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de Oliveira JL, Gómez I, Sánchez J, Soberón M, Polanczyk RA, Bravo A. Performance insights into spray-dryer microencapsulated Bacillus thuringiensis cry pesticidal proteins with gum arabic and maltodextrin for effective pest control. Appl Microbiol Biotechnol 2024; 108:181. [PMID: 38285209 PMCID: PMC10824793 DOI: 10.1007/s00253-023-12990-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Revised: 11/28/2023] [Accepted: 12/26/2023] [Indexed: 01/30/2024]
Abstract
Bacillus thuringiensis (Bt) produces crystals composed mainly of Cry pesticidal proteins with insecticidal activity against pests but are highly susceptible to degradation by abiotic factors. In this sense, encapsulation techniques are designed to improve their performance and lifetime. However, the effects of polymeric matrix encapsulation such as gum arabic and maltodextrin by spray-dryer in the mechanisms of action of Bt kurstaki and Bt aizawai are unknown. We analyzed crystal solubilization, protoxin activation, and receptor binding after microencapsulation and compared them with commercial non-encapsulated products. Microencapsulation did not alter protein crystal solubilization, providing 130 kDa (Cry1 protoxin) and 70 kDa (Cry2 protoxin). Activation with trypsin, chymotrypsin, and larval midgut juice was analyzed, showing that this step is highly efficient, and the protoxins were cleaved producing similar ~ 55 to 65 kDa activated proteins for both formulations. Binding assays with brush border membrane vesicles of Manduca sexta and Spodoptera frugiperda larvae provided a similar binding for both formulations. LC50 bioassays showed no significant differences between treatments but the microencapsulated treatment provided higher mortality against S. frugiperda when subjected to UV radiation. Microencapsulation did not affect the mechanism of action of Cry pesticidal proteins while enhancing protection against UV radiation. These data will contribute to the development of more efficient Bt biopesticide formulations. KEY POINTS: • Microencapsulation did not affect the mechanisms of action of Cry pesticidal proteins produced by Bt. • Microencapsulation provided protection against UV radiation for Bt-based biopesticides. • The study's findings can contribute to the development of more efficient Bt biopesticide formulations.
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Affiliation(s)
- Jhones Luiz de Oliveira
- Department of Agricultural Production Sciences, Faculty of Agronomy and Veterinary Sciences, São Paulo State University (UNESP), Jaboticabal, São Paulo, 14884-900, Brazil
- Department of Molecular Microbiology, Instituto de Biotecnología, Universidad Nacional Autónoma de Mexico, Cuernavaca, Morelos, Mexico
| | - Isabel Gómez
- Department of Molecular Microbiology, Instituto de Biotecnología, Universidad Nacional Autónoma de Mexico, Cuernavaca, Morelos, Mexico
| | - Jorge Sánchez
- Department of Molecular Microbiology, Instituto de Biotecnología, Universidad Nacional Autónoma de Mexico, Cuernavaca, Morelos, Mexico
| | - Mario Soberón
- Department of Molecular Microbiology, Instituto de Biotecnología, Universidad Nacional Autónoma de Mexico, Cuernavaca, Morelos, Mexico
| | - Ricardo Antonio Polanczyk
- Department of Agricultural Production Sciences, Faculty of Agronomy and Veterinary Sciences, São Paulo State University (UNESP), Jaboticabal, São Paulo, 14884-900, Brazil.
| | - Alejandra Bravo
- Department of Molecular Microbiology, Instituto de Biotecnología, Universidad Nacional Autónoma de Mexico, Cuernavaca, Morelos, Mexico.
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He X, Yang Y, Soberón M, Bravo A, Zhang L, Zhang J, Wang Z. Bacillus thuringiensis Cry9Aa Insecticidal Protein Domain I Helices α3 and α4 Are Two Core Regions Involved in Oligomerization and Toxicity. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2024; 72:1321-1329. [PMID: 38175929 DOI: 10.1021/acs.jafc.3c08070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2024]
Abstract
Bacillus thuringiensis Cry9 proteins show high insecticidal activity against different lepidopteran pests. Cry9 could be a valuable alternative to Cry1 proteins because it showed a synergistic effect with no cross-resistance. However, the pore-formation region of the Cry9 proteins is still unclear. In this study, nine mutations of certain Cry9Aa helices α3 and α4 residues resulted in a complete loss of insecticidal activity against the rice pest Chilo suppressalis; however, the protein stability and receptor binding ability of these mutants were not affected. Among these mutants, Cry9Aa-D121R, Cry9Aa-D125R, Cry9Aa-D163R, Cry9Aa-E165R, and Cry9Aa-D167R are unable to form oligomers in vitro, while the oligomers formed by Cry9Aa-R156D, Cry9Aa-R158D, and Cry9Aa-R160D are unstable and failed to insert into the membrane. These data confirmed that helices α3 and α4 of Cry9Aa are involved in oligomerization, membrane insertion, and toxicity. The knowledge of Cry9 pore-forming action may promote its application as an alternative to Cry1 insecticidal proteins.
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Affiliation(s)
- Xiang He
- Anhui Province Engineering Laboratory for Green Pesticide Development and Application, School of Plant Protection, Anhui Agricultural University, Hefei, Anhui Province 230036, China
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Yanchao Yang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Mario Soberón
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Apdo. Postal 510-3, Morelos 62250, Mexico
| | - Alejandra Bravo
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Apdo. Postal 510-3, Morelos 62250, Mexico
| | - Lihong Zhang
- Anhui Province Engineering Laboratory for Green Pesticide Development and Application, School of Plant Protection, Anhui Agricultural University, Hefei, Anhui Province 230036, China
| | - Jie Zhang
- Anhui Province Engineering Laboratory for Green Pesticide Development and Application, School of Plant Protection, Anhui Agricultural University, Hefei, Anhui Province 230036, China
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
| | - Zeyu Wang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
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Torres J, Surya W, Boonserm P. Channel Formation in Cry Toxins: An Alphafold-2 Perspective. Int J Mol Sci 2023; 24:16809. [PMID: 38069132 PMCID: PMC10705909 DOI: 10.3390/ijms242316809] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Revised: 11/23/2023] [Accepted: 11/24/2023] [Indexed: 12/18/2023] Open
Abstract
Bacillus thuringiensis (Bt) strains produce pore-forming toxins (PFTs) that attack insect pests. Information for pre-pore and pore structures of some of these Bt toxins is available. However, for the three-domain (I-III) crystal (Cry) toxins, the most used Bt toxins in pest control, this crucial information is still missing. In these Cry toxins, biochemical data have shown that 7-helix domain I is involved in insertion in membranes, oligomerization and formation of a channel lined mainly by helix α4, whereas helices α1 to α3 seem to have a dynamic role during insertion. In the case of Cry1Aa, toxic against Manduca sexta larvae, a tetrameric oligomer seems to precede membrane insertion. Given the experimental difficulty in the elucidation of the membrane insertion steps, we used Alphafold-2 (AF2) to shed light on possible oligomeric structural intermediates in the membrane insertion of this toxin. AF2 very accurately (<1 Å RMSD) predicted the crystal monomeric and trimeric structures of Cry1Aa and Cry4Ba. The prediction of a tetramer of Cry1Aa, but not Cry4Ba, produced an 'extended model' where domain I helices α3 and α2b form a continuous helix and where hydrophobic helices α1 and α2 cluster at the tip of the bundle. We hypothesize that this represents an intermediate that binds the membrane and precedes α4/α5 hairpin insertion, together with helices α6 and α7. Another Cry1Aa tetrameric model was predicted after deleting helices α1 to α3, where domain I produced a central cavity consistent with an ion channel, lined by polar and charged residues in helix α4. We propose that this second model corresponds to the 'membrane-inserted' structure. AF2 also predicted larger α4/α5 hairpin n-mers (14 ≤n ≤ 17) with high confidence, which formed even larger (~5 nm) pores. The plausibility of these models is discussed in the context of available experimental data and current paradigms.
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Affiliation(s)
- Jaume Torres
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Wahyu Surya
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Panadda Boonserm
- Institute of Molecular Biosciences, Mahidol University, Salaya, Phuttamonthon, Nakhon Pathom 73170, Thailand;
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Wei W, Wang L, Pan S, Wang H, Xia Z, Liu L, Xiao Y, Bravo A, Soberón M, Yang Y, Liu K. Helicoverpa armigera GATAe transcriptional factor regulates the expression of Bacillus thuringiensis Cry1Ac receptor gene ABCC2 by its interplay with additional transcription factors. PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 2023; 194:105516. [PMID: 37532331 DOI: 10.1016/j.pestbp.2023.105516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Revised: 06/12/2023] [Accepted: 07/03/2023] [Indexed: 08/04/2023]
Abstract
Helicoverpa armigera is a worldwide pest that has been efficiently controlled by transgenic plants expressing Bt Cry toxins. To exert toxicity, Cry toxins bind to different receptors located in larval midgut cells. Previously, we reported that GATA transcription factor GATAe activates the expression of multiple H. armigera Cry1Ac receptors in different insect cell lines. Here, the mechanism involved in GATAe regulation of HaABCC2 gene expression, a key receptor of Cry1Ac, was analyzed. HaGATAe gene silencing by RNAi in H. armigera larvae confirmed the activation role of HaGATAe on the expression of HaABCC2 in the midgut. The contribution of all potential GATAe-binding sites was analyzed by site-directed mutagenesis using Hi5 cells expressing a reporter gene under regulation of different modified HaABCC2 promoters. DNA pull-down assays revealed that GATAe bound to different predicted GATA-binding sites and mutations of the different GATAe-binding sites identified two binding sites responsible for the promoter activity. The binding site B9, which is located near the transcription initiator site, has a major contribution on HaABCC2 expression. Also, DNA pull-down assays revealed that all other members of GATA TF family in H. armigera, besides GATAe, HaGATAa, HaGATAb, HaGATAc and HaGATAd also bound to the HaABCC2 promoter and decreased the GATAe dependent promoter activity. Finally, the potential participation in the regulation of HaABCC2 promoter of several TFs other than GATA TFs expressed in the midgut cells was analyzed. HaHR3 inhibited the GATAe dependent activity of the HaABCC2 promoter, while two other midgut-related TFs, HaCDX and HaSox21, also bound to the HaABCC2 promoter region and increased the GATAe dependent promoter activity. All these data showed that GATAe induces HaABCC2 expression by binding to HaGATAe binding sites in the promoter region and that additional TFs participate in modulating the HaGATAe-driven expression of HaABCC2.
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Affiliation(s)
- Wei Wei
- School of Life Sciences, Central China Normal University, Wuhan 430070, China; Applied Biotechnology Center, Wuhan University of Bioengineering, Wuhan 430415, China
| | - Ling Wang
- Institute of Hubei Agriculture Academy, Wuhan 430070, China
| | - Shuang Pan
- School of Life Sciences, Central China Normal University, Wuhan 430070, China
| | - Haixia Wang
- School of Life Sciences, Central China Normal University, Wuhan 430070, China
| | - Zhichao Xia
- School of Life Sciences, Central China Normal University, Wuhan 430070, China
| | - Leilei Liu
- School of Life Sciences, Central China Normal University, Wuhan 430070, China; Applied Biotechnology Center, Wuhan University of Bioengineering, Wuhan 430415, China
| | - Yutao Xiao
- Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen 518120, China
| | - Alejandra Bravo
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca 62250, Morelos, Mexico
| | - Mario Soberón
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca 62250, Morelos, Mexico
| | - Yongbo Yang
- School of Life Sciences, Central China Normal University, Wuhan 430070, China.
| | - Kaiyu Liu
- School of Life Sciences, Central China Normal University, Wuhan 430070, China.
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Pacheco S, Gómez I, Peláez-Aguilar AE, Verduzco-Rosas LA, García-Suárez R, do Nascimento NA, Rivera-Nájera LY, Cantón PE, Soberón M, Bravo A. Structural changes upon membrane insertion of the insecticidal pore-forming toxins produced by Bacillus thuringiensis. FRONTIERS IN INSECT SCIENCE 2023; 3:1188891. [PMID: 38469496 PMCID: PMC10926538 DOI: 10.3389/finsc.2023.1188891] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/18/2023] [Accepted: 04/04/2023] [Indexed: 03/13/2024]
Abstract
Different Bacillus thuringiensis (Bt) strains produce a broad variety of pore-forming toxins (PFTs) that show toxicity against insects and other invertebrates. Some of these insecticidal PFT proteins have been used successfully worldwide to control diverse insect crop pests. There are several studies focused on describing the mechanism of action of these toxins that have helped to improve their performance and to cope with the resistance evolved by different insects against some of these proteins. However, crucial information that is still missing is the structure of pores formed by some of these PFTs, such as the three-domain crystal (Cry) proteins, which are the most commercially used Bt toxins in the biological control of insect pests. In recent years, progress has been made on the identification of the structural changes that certain Bt insecticidal PFT proteins undergo upon membrane insertion. In this review, we describe the models that have been proposed for the membrane insertion of Cry toxins. We also review the recently published structures of the vegetative insecticidal proteins (Vips; e.g. Vip3) and the insecticidal toxin complex (Tc) in the membrane-inserted state. Although different Bt PFTs show different primary sequences, there are some similarities in the three-dimensional structures of Vips and Cry proteins. In addition, all PFTs described here must undergo major structural rearrangements to pass from a soluble form to a membrane-inserted state. It is proposed that, despite their structural differences, all PFTs undergo major structural rearrangements producing an extended α-helix, which plays a fundamental role in perforating their target membrane, resulting in the formation of the membrane pore required for their insecticidal activity.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - Alejandra Bravo
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, Mexico
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Xiong L, Liu Z, Li J, Yao S, Li Z, Chen X, Shen L, Zhang Z, Li Y, Hou Q, Zhang Y, You M, Yuchi Z, You S. Analysis of the Effect of Plutella xylostella Polycalin and ABCC2 Transporter on Cry1Ac Susceptibility by CRISPR/Cas9-Mediated Knockout. Toxins (Basel) 2023; 15:toxins15040273. [PMID: 37104211 PMCID: PMC10145054 DOI: 10.3390/toxins15040273] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Revised: 03/28/2023] [Accepted: 04/04/2023] [Indexed: 04/28/2023] Open
Abstract
Many insects, including the Plutella xylostella (L.), have developed varying degrees of resistance to many insecticides, including Bacillus thuringiensis (Bt) toxins, the bioinsecticides derived from Bt. The polycalin protein is one of the potential receptors for Bt toxins, and previous studies have confirmed that the Cry1Ac toxin can bind to the polycalin protein of P. xylostella, but whether polycalin is associated with the resistance of Bt toxins remains controversial. In this study, we compared the midgut of larvae from Cry1Ac-susceptible and -resistant strains, and found that the expression of the Pxpolycalin gene was largely reduced in the midgut of the resistant strains. Moreover, the spatial and temporal expression patterns of Pxpolycalin showed that it was mainly expressed in the larval stage and midgut tissue. However, genetic linkage experiments showed that the Pxpolycalin gene and its transcript level were not linked to Cry1Ac resistance, whereas both the PxABCC2 gene and its transcript levels were linked to Cry1Ac resistance. The larvae fed on a diet containing the Cry1Ac toxin showed no significant change in the expression of the Pxpolycalin gene in a short term. Furthermore, the knockout of polycalin and ATP-binding cassette transporter subfamily C2 (ABCC2) genes separately by CRISPR/Cas9 technology resulted in resistance to decreased susceptibility to Cry1Ac toxin. Our results provide new insights into the potential role of polycalin and ABCC2 proteins in Cry1Ac resistance and the mechanism underlying the resistance of insects to Bt toxins.
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Affiliation(s)
- Lei Xiong
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Institute of Applied Ecology, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Joint International Research Laboratory of Ecological Pest Control, Ministry of Education, Fuzhou 350002, China
| | - Zhaoxia Liu
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Institute of Applied Ecology, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Joint International Research Laboratory of Ecological Pest Control, Ministry of Education, Fuzhou 350002, China
- College of Oceanology and Food Science, Quanzhou Normal University, Quanzhou 362000, China
| | - Jingge Li
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Institute of Applied Ecology, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Joint International Research Laboratory of Ecological Pest Control, Ministry of Education, Fuzhou 350002, China
| | - Shuyuan Yao
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Institute of Applied Ecology, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Joint International Research Laboratory of Ecological Pest Control, Ministry of Education, Fuzhou 350002, China
| | - Zeyun Li
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Institute of Applied Ecology, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Joint International Research Laboratory of Ecological Pest Control, Ministry of Education, Fuzhou 350002, China
| | - Xuanhao Chen
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Institute of Applied Ecology, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Joint International Research Laboratory of Ecological Pest Control, Ministry of Education, Fuzhou 350002, China
| | - Lingling Shen
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Institute of Applied Ecology, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Joint International Research Laboratory of Ecological Pest Control, Ministry of Education, Fuzhou 350002, China
| | - Zhen Zhang
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Institute of Applied Ecology, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Joint International Research Laboratory of Ecological Pest Control, Ministry of Education, Fuzhou 350002, China
| | - Yongbin Li
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Institute of Applied Ecology, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Joint International Research Laboratory of Ecological Pest Control, Ministry of Education, Fuzhou 350002, China
| | - Qing Hou
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Institute of Applied Ecology, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Joint International Research Laboratory of Ecological Pest Control, Ministry of Education, Fuzhou 350002, China
| | - Yuhang Zhang
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Institute of Applied Ecology, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Joint International Research Laboratory of Ecological Pest Control, Ministry of Education, Fuzhou 350002, China
| | - Minsheng You
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Institute of Applied Ecology, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Joint International Research Laboratory of Ecological Pest Control, Ministry of Education, Fuzhou 350002, China
| | - Zhiguang Yuchi
- School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, China
| | - Shijun You
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Institute of Applied Ecology, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, Fujian Agriculture and Forestry University, Fuzhou 350002, China
- Joint International Research Laboratory of Ecological Pest Control, Ministry of Education, Fuzhou 350002, China
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Zhang J, Liu Y, Li S, Zhou Q, Zhang L, Zhang S, Zhou X, Wu C, Qian ZY. A 90-day rodent feeding study with grain for genetically modified maize L4 conferring insect resistance and glyphosate tolerance. Food Chem Toxicol 2023; 176:113733. [PMID: 36966880 DOI: 10.1016/j.fct.2023.113733] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Revised: 03/06/2023] [Accepted: 03/15/2023] [Indexed: 04/16/2023]
Abstract
A 90-day rat feeding study was performed to conduct a safety assessment on L4, a multi-gene genetically modified maize, conferring "Bt" insect resistance and glyphosate tolerance. A total of 140 Wistar rats were assigned to seven groups, 10 animals/group/sex, which comprised three genetically modified groups fed diets containing different concentrations of L4, three corresponding non-genetically modified groups fed diets containing different concentrations of zheng58 (parent plants), and a basal diet group fed the standard basal diet for 13 weeks. The fed diets contained L4 and Zheng58 at w/w% percentages of 12.5%, 25.0%, and 50% of the total. Animals were evaluated on some research parameters, including general behaviour, body weight/gain, feed consumption/efficiency, ophthalmology, clinical pathology, organ weights, and histopathology. Throughout the feeding trial, all animals were in good condition. No mortality and no biologically relevant effects or toxicologically significant alterations were observed in the total research parameters of the rats in the genetically modified groups compared with those in the basal diet group or their corresponding non-genetically modified groups. No adverse effects were observed in any of the animals. The results indicated that L4 is as safe and wholesome as conventional, non-genetically modified control maize.
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Affiliation(s)
- Jing Zhang
- Tianjin Centers for Disease Control and Prevention, Tianjin, 300011, China
| | - Yinghua Liu
- Tianjin Centers for Disease Control and Prevention, Tianjin, 300011, China
| | - Shufei Li
- Tianjin Centers for Disease Control and Prevention, Tianjin, 300011, China
| | - Qinghong Zhou
- Tianjin Centers for Disease Control and Prevention, Tianjin, 300011, China
| | - Li Zhang
- Tianjin Centers for Disease Control and Prevention, Tianjin, 300011, China
| | - Shujing Zhang
- Tianjin Centers for Disease Control and Prevention, Tianjin, 300011, China
| | - Xiaoli Zhou
- Tianjin Centers for Disease Control and Prevention, Tianjin, 300011, China
| | - Chao Wu
- Tianjin Centers for Disease Control and Prevention, Tianjin, 300011, China
| | - Zhi Yong Qian
- Tianjin Centers for Disease Control and Prevention, Tianjin, 300011, China.
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8
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Yang Y, Lu K, Qian J, Guo J, Xu H, Lu Z. Identification and characterization of ABC proteins in an important rice insect pest, Cnaphalocrocis medinalis unveil their response to Cry1C toxin. Int J Biol Macromol 2023; 237:123949. [PMID: 36894061 DOI: 10.1016/j.ijbiomac.2023.123949] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Revised: 03/01/2023] [Accepted: 03/03/2023] [Indexed: 03/09/2023]
Abstract
Rice leaffolder (Cnaphalocrocis medinalis) is an important insect pest in paddy fields. Due to their essential role in the physiology and insecticidal resistance, ATP-binding cassette (ABC) proteins were studied in many insects. In this study, we identified the ABC proteins in C. medinalis through genomic data and analyzed their molecular characteristics. A total of 37 sequences with nucleotide-binding domain (NBD) were identified as ABC proteins and belonged to eight families (ABCA-ABCH). Four structure styles of ABC proteins were found in C. medinalis, including full structure, half structure, single structure, and ABC2 structure. In addition to these structures, TMD-NBD-TMD, NBD-TMD-NBD, and NBD-TMD-NBD-NBD were found in C. medinalis ABC proteins. Docking studies suggested that in addition to the soluble ABC proteins, other ABC proteins including ABCC4, ABCH1, ABCG3, ABCB5, ABCG1, ABCC7, ABCB3, ABCA3, and ABCC5 binding with Cry1C had higher weighted scores. The upregulation of ABCB1 and downregulation of ABCB3, ABCC1, ABCC7, ABCG1, ABCG3, and ABCG6 were associated with the C. medinalis response to Cry1C toxin. Collectively, these results help elucidate the molecular characteristics of C. medinalis ABC proteins, pave the way for further functional studies of C. medinalis ABC proteins, including their interaction with Cry1C toxin, and provide potential insecticide targets.
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Affiliation(s)
- Yajun Yang
- State Key Laboratory for Managing Biotic and Chemical Treats to the Quality and Safety of Agro-products, Key Laboratory of Biotechnology in Plant Protection, Ministry of Agriculture and Rural Affairs, Institute of Plant Protection and Microbiology, Zhejiang Academy of Agriculture Sciences, Hangzhou 310021, China
| | - Ke Lu
- State Key Laboratory for Managing Biotic and Chemical Treats to the Quality and Safety of Agro-products, Key Laboratory of Biotechnology in Plant Protection, Ministry of Agriculture and Rural Affairs, Institute of Plant Protection and Microbiology, Zhejiang Academy of Agriculture Sciences, Hangzhou 310021, China; Department of Entomology, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China
| | - Jianing Qian
- State Key Laboratory for Managing Biotic and Chemical Treats to the Quality and Safety of Agro-products, Key Laboratory of Biotechnology in Plant Protection, Ministry of Agriculture and Rural Affairs, Institute of Plant Protection and Microbiology, Zhejiang Academy of Agriculture Sciences, Hangzhou 310021, China
| | - Jiawen Guo
- State Key Laboratory for Managing Biotic and Chemical Treats to the Quality and Safety of Agro-products, Key Laboratory of Biotechnology in Plant Protection, Ministry of Agriculture and Rural Affairs, Institute of Plant Protection and Microbiology, Zhejiang Academy of Agriculture Sciences, Hangzhou 310021, China
| | - Hongxing Xu
- State Key Laboratory for Managing Biotic and Chemical Treats to the Quality and Safety of Agro-products, Key Laboratory of Biotechnology in Plant Protection, Ministry of Agriculture and Rural Affairs, Institute of Plant Protection and Microbiology, Zhejiang Academy of Agriculture Sciences, Hangzhou 310021, China.
| | - Zhongxian Lu
- State Key Laboratory for Managing Biotic and Chemical Treats to the Quality and Safety of Agro-products, Key Laboratory of Biotechnology in Plant Protection, Ministry of Agriculture and Rural Affairs, Institute of Plant Protection and Microbiology, Zhejiang Academy of Agriculture Sciences, Hangzhou 310021, China.
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Fabrick JA, Li X, Carrière Y, Tabashnik BE. Molecular Genetic Basis of Lab- and Field-Selected Bt Resistance in Pink Bollworm. INSECTS 2023; 14:insects14020201. [PMID: 36835770 PMCID: PMC9959750 DOI: 10.3390/insects14020201] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Revised: 02/03/2023] [Accepted: 02/14/2023] [Indexed: 05/17/2023]
Abstract
Transgenic crops producing insecticidal proteins from the bacterium Bacillus thuringiensis (Bt) control some important insect pests. However, evolution of resistance by pests reduces the efficacy of Bt crops. Here we review resistance to Bt cotton in the pink bollworm, Pectinophora gossypiella, one of the world's most damaging pests of cotton. Field outcomes with Bt cotton and pink bollworm during the past quarter century differ markedly among the world's top three cotton-producing countries: practical resistance in India, sustained susceptibility in China, and eradication of this invasive lepidopteran pest from the United States achieved with Bt cotton and other tactics. We compared the molecular genetic basis of pink bollworm resistance between lab-selected strains from the U.S. and China and field-selected populations from India for two Bt proteins (Cry1Ac and Cry2Ab) produced in widely adopted Bt cotton. Both lab- and field-selected resistance are associated with mutations affecting the cadherin protein PgCad1 for Cry1Ac and the ATP-binding cassette transporter protein PgABCA2 for Cry2Ab. The results imply lab selection is useful for identifying genes important in field-evolved resistance to Bt crops, but not necessarily the specific mutations in those genes. The results also suggest that differences in management practices, rather than genetic constraints, caused the strikingly different outcomes among countries.
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Affiliation(s)
- Jeffrey A. Fabrick
- USDA ARS, U.S. Arid Land Agricultural Research Center, Maricopa, AZ 85138, USA
- Correspondence:
| | - Xianchun Li
- Department of Entomology, University of Arizona, Tucson, AZ 85721, USA
| | - Yves Carrière
- Department of Entomology, University of Arizona, Tucson, AZ 85721, USA
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10
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García-Gomez BI, Sánchez TA, Cano SN, do Nascimento NA, Bravo A, Soberón M. Insect chaperones Hsp70 and Hsp90 cooperatively enhance toxicity of Bacillus thuringiensis Cry1A toxins and counteract insect resistance. Front Immunol 2023; 14:1151943. [PMID: 37153577 PMCID: PMC10157212 DOI: 10.3389/fimmu.2023.1151943] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Accepted: 04/11/2023] [Indexed: 05/09/2023] Open
Abstract
Bacillus thuringiensis (Bt) produces different insecticidal proteins effective for pest control. Among them, Cry insecticidal proteins have been used in transgenic plants for the control of insect pests. However, evolution of resistance by insects endangers this technology. Previous work showed that the lepidopteran insect Plutella xylostella PxHsp90 chaperone enhanced the toxicity of Bt Cry1A protoxins by protecting them from degradation by the larval gut proteases and by enhancing binding of the protoxin to its receptors present in larval midgut cells. In this work, we show that PxHsp70 chaperone also protects Cry1Ab protoxin from gut proteases degradation, enhancing Cry1Ab toxicity. We also show that both PxHsp70 and PxHsp90 chaperones act cooperatively, increasing toxicity and the binding of Cry1Ab439D mutant, affected in binding to midgut receptors, to cadherin receptor. Also, insect chaperones recovered toxicity of Cry1Ac protein to a Cry1Ac-highly resistant P. xylostella population, NO-QAGE, that has a disruptive mutation in an ABCC2 transporter linked to Cry1Ac resistance. These data show that Bt hijacked an important cellular function for enhancing its infection capability, making use of insect cellular chaperones for enhancing Cry toxicity and for lowering the evolution of insect resistance to these toxins.
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11
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Pacheco S, Gómez I, Soberón M, Bravo A. A major conformational change of N-terminal helices of Bacillus thuringiensis Cry1Ab insecticidal protein is necessary for membrane insertion and toxicity. FEBS J 2022; 290:2692-2705. [PMID: 36560841 DOI: 10.1111/febs.16710] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Revised: 12/01/2022] [Accepted: 12/21/2022] [Indexed: 12/24/2022]
Abstract
Pore forming toxins rely on oligomerization for membrane insertion to kill their targets. Bacillus thuringiensis produces insecticidal Cry-proteins composed of three domains that form pores that kill the insect larvae. Domain I is involved in oligomerization and membrane insertion, whereas Domains II and III participate in receptor binding and specificity. However, the structural changes involved in membrane insertion of these proteins remain unsolved. The most widely accepted model for membrane insertion, the 'umbrella model', proposed that the α-4/α-5 hairpin of Domain I swings away and is inserted into the membrane. To determine the topology of Cry1Ab in the membrane, disulfide bonds linking α-helices of Domain I were introduced to restrict their movement. Disulfide bonds between helices α-2/α-3 or α-3/α-4 lost oligomerization and toxicity, indicating that movement of these helices is needed for insecticidal activity. By contrast, disulfide bonds linking helices α-5/α-6 did not affect toxicity, which contradicts the 'umbrella model'. Additionally, Föster resonance energy transfer closest approach analyses measuring distances of different points in the toxin to the membrane plane and collisional quenching assays analysing the protection of specific fluorescent-labeled residues to the soluble potassium iodide quencher in the membrane inserted state were performed. Overall, the data show that Domain I from Cry1Ab may undergo a major conformational change during its membrane insertion, where the N-terminal region (helices α-1 to α-4) participates in oligomerization and toxicity, probably forming an extended helix. These data break a paradigm, showing a new 'folding white-cane model', which better explains the structural changes of Cry toxins during insertion into the membrane.
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Affiliation(s)
- Sabino Pacheco
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), Cuernavaca, Mexico
| | - Isabel Gómez
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), Cuernavaca, Mexico
| | - Mario Soberón
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), Cuernavaca, Mexico
| | - Alejandra Bravo
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), Cuernavaca, Mexico
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12
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The Crystal Structure of Bacillus thuringiensis Tpp80Aa1 and Its Interaction with Galactose-Containing Glycolipids. Toxins (Basel) 2022; 14:toxins14120863. [PMID: 36548760 PMCID: PMC9784298 DOI: 10.3390/toxins14120863] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Revised: 11/21/2022] [Accepted: 11/24/2022] [Indexed: 12/13/2022] Open
Abstract
Tpp80Aa1 from Bacillus thuringiensis is a Toxin_10 family protein (Tpp) with reported action against Culex mosquitoes. Here, we demonstrate an expanded target range, showing Tpp80Aa1 is also active against the larvae of Anopheles gambiae and Aedes aegypti mosquitoes. We report the first crystal structure of Tpp80Aa1 at a resolution of 1.8 Å, which shows Tpp80Aa1 consists of two domains: an N-terminal β-trefoil domain resembling a ricin B lectin and a C-terminal putative pore-forming domain sharing structural similarity with the aerolysin family. Similar to other Tpp family members, we observe Tpp80Aa1 binds to the mosquito midgut, specifically the posterior midgut and the gastric caecum. We also identify that Tpp80Aa1 can interact with galactose-containing glycolipids and galactose, and this interaction is critical for exerting full insecticidal action against mosquito target cell lines.
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13
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Zhang C, Wei J, Naing ZL, Soe ET, Tang J, Liang G. Up-regulated serpin gene involved in Cry1Ac resistance in Helicoverpa armigera. PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 2022; 188:105269. [PMID: 36464374 DOI: 10.1016/j.pestbp.2022.105269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Revised: 09/29/2022] [Accepted: 10/15/2022] [Indexed: 06/17/2023]
Abstract
Insect resistance to Bacillus thuringiensis (Bt) is a critical limiting factor for applying the Bt crops. Some studies indicated that decreased protoxin activation because of lower enzymatic activities of trypsin and chymotrypsin and increased expression of serpin might involve in Bt resistance. Our previous study identified an endogenous serpin could inhibit the midgut proteases to activate Cry1Ac and reduce the insecticide activity to Helicoverpa armigera. We hypothesis that up-regulated serpin involve in resistance via inhibiting enzymatic activities of trypsin and chymotrypsin to decrease protoxin activation. Herein, we found the serpin-e gene relative expression in midgut was significantly higher in the LF30 resistant strain than that in the susceptible strain during all developmental stages. Importantly, RNAi-mediated silencing of serpin-e gene expression caused 4.46-fold mortality changes in LF30 strain, but the trypsin and chymotrypsin proteases activities were only changed 0.79-fold and 2.22-fold. In addition, although proteases activities were significantly lower in LF30 strain than that in the susceptible strain, the resistance ratios of LF30 to Cry1Ac protoxin and to activated Cry1Ac toxin were no difference. The results indicated serpins caused insect resistance to Cry1Ac protoxins partly through inhibiting the trypsin and chymotrypsin proteases activities, but it also existed other mechanisms in LF30.
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Affiliation(s)
- Caihong Zhang
- State key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, PR China
| | - Jizhen Wei
- College of Plant Protection, Henan Agricultural University, Zhengzhou 450002, PR China
| | - Zaw Lin Naing
- State key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, PR China
| | - Ei Thinzar Soe
- State key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, PR China
| | - Jinrong Tang
- State key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, PR China
| | - Gemei Liang
- State key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, PR China; Western Agricultural Research Center, Chinese Academy of Agricultural Sciences, Changji 831100,PR China.
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14
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Functional Diversity of the Lepidopteran ATP-Binding Cassette Transporters. J Mol Evol 2022; 90:258-270. [PMID: 35513601 DOI: 10.1007/s00239-022-10056-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Accepted: 04/05/2022] [Indexed: 10/18/2022]
Abstract
The ATP-binding cassette (ABC) transporter gene family is ubiquitous in the living world. ABC proteins bind and hydrolyze ATP to transport a myriad of molecules across various lipid-containing membrane systems. They have been studied well in plants for transport of a variety of compounds and particularly, in vertebrates due to their direct involvement in resistance mechanisms against several toxic molecules/metabolites. ABC transporters in insects are found within large multigene families involved in the efflux of chemical insecticides and toxic/undesired metabolites originating from food and endogenous metabolism. This review deals with ABC transporter subfamilies of few agronomically important Lepidopteran pests. The transcriptional dynamics and regulation of ABC transporters during insect development emphasizes their functional diversity against insecticides, Cry toxins, and plant specialized metabolites. To generate insights about molecular function and physiological roles of ABCs, functional and structural characterization is necessary. Also, expansion and divergence of ABC transporter gene subfamilies in Lepidopteran insects needs more systematic investigation. We anticipate that newer methods of insect control in agriculture can benefit from an understanding of ABC transporter interactions with a vast range of natural specialized molecules and synthetic compounds.
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Bacillus thuringiensis Cry1Ac Protoxin and Activated Toxin Exert Differential Toxicity Due to a Synergistic Interplay of Cadherin with ABCC Transporters in the Cotton Bollworm. Appl Environ Microbiol 2022; 88:e0250521. [PMID: 35262369 DOI: 10.1128/aem.02505-21] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Bacillus thuringiensis Cry proteins are used worldwide for insect control. It was proposed that Cry-protoxins must be converted into activated toxin by proteases to bind midgut cell proteins to kill insects. However, Cry-protoxins also bind to midgut proteins and kill insects that have evolved resistance to activated toxins suggesting an independent toxicity pathway. Cadherin (CAD) and ABCC transporters are recognized as important receptors for Cry proteins. Here we constructed different Helicoverpa armigera mutations in these receptors by CRISPR/Cas9. HaCAD-KO mutant showed much higher resistance to Cry1Ac activated toxin than to Cry1Ac protoxin. In contrast, the HaABCC2-M and HaABCC3-M mutants showed higher resistance to Cry1Ac-protoxin than to activated toxin. However, in the double HaABCC2/3-KO mutant, very high levels of resistance were observed to both Cry1Ac protoxin and activated toxin, supporting that both ABC transporters have redundant functions for these two proteins. In addition, Hi5 cells transfected with HaCAD were susceptible only to the activated toxin but not to protoxin. In contrast, both forms of Cry1Ac were similarly toxic to Hi5 cells expressing HaABCC2 or HaABCC3. Co-expression of HaCAD with HaABCC2 or HaABCC3 revealed a more important synergistic effect for activated toxin compared to protoxin. Overall, our results show that toxicity of Cry1Ac activated toxin involves synergistic interplay of HaCAD with ABCC transporters, while the Cry1Ac protoxin toxicity is mainly mediated by ABCC transporters with little participation of HaCAD. These data help to understand the mode of action of Cry proteins that will be relevant to enhance efficacy and durability of Bt-crops. IMPORTANCE Better understanding of the mode of action of Bacillus thuringiensis toxins is beneficial for the sustainable application of Bt crops. It is generally accepted that Cry-protoxins need to be activated by proteases to bind with midgut cell proteins and exert toxicity against insects. Here, we provide new insights into the toxic pathway of Cry proteins in the cotton bollworm. First, our results demonstrate that Cry1Ac protoxin is able to exert cytotoxicity against the insect cells expressing ABCC transporters. Second, we reveal that CAD plays a critical role in the different toxicity of protoxin and toxin by facilitating a synergistic interplay with ABCC transporters. Our results provide in vivo and in vitro experimental evidence supporting that Cry1Ac protoxin exerts toxicity against H. armigera via different steps from that of toxin. These new findings on the mode of action of Cry proteins could be beneficial for efficacy enhancement and durability of Bt-crops.
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Khorramnejad A, Bel Y, Talaei-Hassanloui R, Escriche B. Activation of Bacillus thuringiensis Cry1I to a 50 kDa stable core impairs its full toxicity to Ostrinia nubilalis. Appl Microbiol Biotechnol 2022; 106:1745-1758. [PMID: 35138453 PMCID: PMC8882101 DOI: 10.1007/s00253-022-11808-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Revised: 12/28/2021] [Accepted: 01/26/2022] [Indexed: 11/30/2022]
Abstract
Bacillus thuringiensis Cry1I insecticidal proteins are structurally similar to other three-domain Cry proteins, although their size, activity spectrum, and expression at the stationary phase are unique among other members of the Cry1 family. The mode of action of Cry1 proteins is not completely understood but the existence of an activation step prior to specific binding is widely accepted. In this study, we attempted to characterize and determine the importance of the activation process in the mode of action of Cry1I, as Cry1Ia protoxin or its partially processed form showed significantly higher toxicity to Ostrinia nubilalis than the fully processed protein either activated with trypsin or with O. nubilalis midgut juice. Oligomerization studies showed that Cry1Ia protoxin, in solution, formed dimers spontaneously, and the incubation of Cry1Ia protoxin with O. nubilalis brush border membrane vesicles (BBMV) promoted the formation of dimers of the partially processed form. While no oligomerization of fully activated proteins after incubation with BBMV was detected. The results of the in vitro competition assays showed that both the Cry1Ia protoxin and the approx. 50 kDa activated proteins bind specifically to the O. nubilalis BBMV and compete for the same binding sites. Accordingly, the in vivo binding competition assays show a decrease in toxicity following the addition of an excess of 50 kDa activated protein. Consequently, as full activation of Cry1I protein diminishes its toxicity against lepidopterans, preventing or decelerating proteolysis might increase the efficacy of this protein in Bt-based products. KEY POINTS: • Processing Cry1I to a 50 kDa stable core impairs its full toxicity to O. nubilalis • Partially processed Cry1Ia protoxin retains the toxicity of protoxin vs O. nubilalis • Protoxin and its final processed forms compete for the same functional binding sites.
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Affiliation(s)
- Ayda Khorramnejad
- Laboratory of Biotechnological Control of Pests, Departamento de Genética, Instituto BioTecMed, Universitat de València, Burjassot, València, Spain.,Laboratory of Biological Control of Pest, Department of Plant Protection, College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran
| | - Yolanda Bel
- Laboratory of Biotechnological Control of Pests, Departamento de Genética, Instituto BioTecMed, Universitat de València, Burjassot, València, Spain.
| | - Reza Talaei-Hassanloui
- Laboratory of Biological Control of Pest, Department of Plant Protection, College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran
| | - Baltasar Escriche
- Laboratory of Biotechnological Control of Pests, Departamento de Genética, Instituto BioTecMed, Universitat de València, Burjassot, València, Spain.
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Roberto Raúl SG, Damaris IA, Ángel de Jesús JC, Leticia MF. Cry1Ac Protoxin Confers Antitumor Adjuvant Effect in a Triple-Negative Breast Cancer Mouse Model by Improving Tumor Immunity. BREAST CANCER: BASIC AND CLINICAL RESEARCH 2022; 16:11782234211065154. [PMID: 35002244 PMCID: PMC8738886 DOI: 10.1177/11782234211065154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Accepted: 11/17/2021] [Indexed: 12/07/2022] Open
Abstract
The Cry1Ac protoxin from Bacillus thuringiensis is a systemic
and mucosal adjuvant, able to confer protective immunity in different infection
murine models and induce both Th1 and TCD8+ cytotoxic lymphocyte responses,
which are required to induce antitumor immunity. The Cry1Ac toxin, despite
having not being characterized as an adjuvant, has also proved to be immunogenic
and able to activate macrophages. Here, we investigated the potential antitumor
adjuvant effect conferred by the Cry1Ac protoxin and Cry1Ac toxin in a triple
negative breast cancer (TNBC) murine model. First, we evaluated the ability of
Cry1Ac proteins to improve dendritic cell (DC) activation and cellular response
through intraperitoneal (i.p.) coadministration with the 4T1 cellular lysate.
Mice coadministered with the Cry1Ac protoxin showed an increase in the number
and activation of CD11c+MHCII- and CD11c+MHCII+low in the peritoneal
cavity and an increase in DC activation (CD11c+MHCII+) in the spleen. Cry1Ac
protoxin increased the proliferation of TCD4+ and TCD8+ lymphocytes in the
spleen and mesenteric lymph nodes (MLN), while the Cry1Ac toxin only increased
the proliferation of TCD4+ and TCD8+ in the MLN. Remarkably, when tested in the
in vivo TNBC mouse model, prophylactic immunizations with 4T1 lysates plus the
Cry1Ac protoxin protected mice from developing tumors. The antitumor effect
conferred by the Cry1Ac protoxin also increased specific cytotoxic T cell
responses, and prevented the typical tumor-related decrease of T cells
(TCD3+ and TCD4+) as well the increase of myeloid-derived suppressor cells
(MDSC) in spleen. Also in the tumor microenvironment of mice coadministered
twice with Cry1Ac protoxin immunological improvements were found such as
reductions in immunosupressive populations (T regulatory lymphocytes and MDSC)
along with increases in macrophages upregulating CD86. These results show a
differential antitumor adjuvant capability of Cry1Ac proteins, highlighting the
ability of Cry1Ac protoxin to enhance local and systemic tumor immunity in TNBC.
Finally, using a therapeutic approach, we evaluated the coadministration of
Cry1Ac protoxin with doxorubicin. A significant reduction in tumor volume and
lung metastasis was found, with increased intratumoral levels of tumor necrosis
factor-α and IL-6 with respect to the vehicle group, further supporting its
antitumor applicability.
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Affiliation(s)
- Servin-Garrido Roberto Raúl
- Laboratorio de Inmunidad en Mucosas, Unidad de Investigación en Biomedicina, Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de México, Avenida de los Barrios 1 Los Reyes Iztacala CP 54090, Tlalnepantla, Estado de México, México
| | - Ilhuicatzi-Alvarado Damaris
- Laboratorio de Inmunidad en Mucosas, Unidad de Investigación en Biomedicina, Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de México, Avenida de los Barrios 1 Los Reyes Iztacala CP 54090, Tlalnepantla, Estado de México, México
| | - Jiménez-Chávez Ángel de Jesús
- Laboratorio de Inmunidad en Mucosas, Unidad de Investigación en Biomedicina, Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de México, Avenida de los Barrios 1 Los Reyes Iztacala CP 54090, Tlalnepantla, Estado de México, México
| | - Moreno-Fierros Leticia
- Laboratorio de Inmunidad en Mucosas, Unidad de Investigación en Biomedicina, Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de México, Avenida de los Barrios 1 Los Reyes Iztacala CP 54090, Tlalnepantla, Estado de México, México
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Bacillus thuringiensis Cry1Ab Domain III β-16 Is Involved in Binding to Prohibitin, Which Correlates with Toxicity against Helicoverpa armigera (Lepidoptera: Noctuidae). Appl Environ Microbiol 2021; 87:AEM.01930-20. [PMID: 33127814 DOI: 10.1128/aem.01930-20] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Accepted: 10/24/2020] [Indexed: 01/09/2023] Open
Abstract
Helicoverpa armigera is a major insect pest of several crops worldwide. This insect is susceptible to some Bacillus thuringiensis (Bt) Cry insecticidal proteins expressed in transgenic crops or used in biopesticides. Previously, we identified H. armigera prohibitin (HaPHB) as a Cry1Ac-binding protein. Here, we further analyzed the potential role of PHB as a Cry toxin receptor in comparison to cadherin (CAD), well recognized as a Cry1Ac receptor. HaPHB-2 midgut protein and HaCAD toxin-binding region (TBR) fragment from H. armigera were expressed in Escherichia coli cells, and binding assays with different Cry1 toxins were performed. We demonstrated that Cry1Ab, Cry1Ac, and Cry1Fa toxins bound to HaPHB-2 in a manner similar to that seen with HaCAD-TBR. Different Cry1Ab mutant toxins located in domain II (Cry1AbF371A and Cry1AbG439D) or domain III (Cry1AbL511A and Cry1AbN514A), which were previously characterized and found to be affected in receptor binding, were analyzed regarding their binding interaction with HaPHB-2 and toxicity against H. armigera One β-16 mutant (Cry1AbN514A) showed increased binding to HaPHB-2 that correlated with 6-fold-higher toxicity against H. armigera, whereas the other β-16 mutant (Cry1AbL511A) was affected in binding to HaPHB-2 and lost toxicity against H. armigera Our data indicate that β-16 from domain III of Cry1Ab is involved in interactions with HaPHB-2 and in toxicity. This report identifies a region of Cry1Ab involved in binding to HaPHB-2 from a Lepidoptera insect, suggesting that this protein may participate as a novel receptor in the mechanism of action of the Cry1 toxins in H. armigera IMPORTANCE Helicoverpa armigera is a polyphagous pest that feeds on important crops worldwide. This insect pest is sensitive to different Cry1 toxins from Bacillus thuringiensis In this study, we analyzed the potential role of PHB-2 as a Cry1 toxin receptor in comparison to CAD. We show that different Cry1 toxins bound to HaPHB-2 and HaCAD-TBR similarly and identify β-16 from domain III of Cry1Ab as a binding region involved in the interaction with HaPHB-2 and in toxicity. This report characterized HaPHB-Cry1 binding interaction, providing novel insights into potential target sites for improving Cry1 toxicity against H. armigera.
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Bacillus thuringiensis Cry1Ab Domain III β-22 Mutants with Enhanced Toxicity to Spodoptera frugiperda (J. E. Smith). Appl Environ Microbiol 2020; 86:AEM.01580-20. [PMID: 32887720 DOI: 10.1128/aem.01580-20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Accepted: 08/20/2020] [Indexed: 11/20/2022] Open
Abstract
The fall armyworm, Spodoptera frugiperda, is an invasive maize pest that has spread from the Americas into Africa and Asia and causes severe crop damage worldwide. Most populations of S. frugiperda show low susceptibility to Bacillus thuringiensis (Bt) Cry1Ab or Cry1Ac toxins, which have been proved to be effective against several other lepidopteran pests. In addition, S. frugiperda has evolved resistance to transgenic maize expressing Cry1Fa toxin. The specificity and toxicity of Cry toxins are determined by their binding to different larval midgut proteins, such as aminopeptidase N (APN), alkaline phosphatase (ALP), and cadherin (CAD), among other proteins, by means of exposed domain II loop regions and also by the domain III β-sheets β-16 and β-22. Here, we analyzed different Cry1Ab mutants with mutations in the domain III β-22 region. Alanine-scanning mutagenesis of this region revealed that all mutants showed increased toxicity against a nonsusceptible Cry1Ab S. frugiperda population. Further analysis of the mutant toxin Cry1AbS587A (bearing a mutation of S to A at position 587) revealed that, compared to Cry1Ab, it showed significantly increased toxicity to three other S. frugiperda populations from Mexico but retained similar toxicity to Manduca sexta larvae. Cry1AbS587A bound to brush border membrane vesicles (BBMV), and its higher toxicity correlated with higher binding affinities to APN, ALP, and CAD recombinant proteins. Furthermore, silencing the expression of APN1 and CAD receptors in S. frugiperda larvae by RNA interference (RNAi) showed that Cry1AbS587A toxicity relied on CAD expression, in contrast to Cry1Ab. These data support the idea that the increased toxicity of Cry1AbS587A to S. frugiperda is in part due to an improved binding interaction with the CAD receptor.IMPORTANCE Spodoptera frugiperda is an important worldwide pest of maize and rice crops that has evolved resistance to Cry1Fa-expressing maize in different countries. Therefore, identification of additional toxins with different modes of action is needed to provide alternative tools to control this insect pest. Bacillus thuringiensis (Bt) Cry1Ab and Cry1Ac toxins are highly active against several important lepidopteran pests but show varying and low levels of toxicity against different S. frugiperda populations. Thus, the identification of Cry1A mutants that gain toxicity to S. frugiperda and retain toxicity to other pests could be of great value to produce transgenic crops that resist a broader spectrum of lepidopteran pests. Here, we characterized Cry1Ab domain III β-22 mutants, and we found that a Cry1AbS587A mutant displayed increased toxicity against different S. frugiperda populations. Thus, Cry1AbS587A could be a good toxin candidate to produce transgenic maize with broader efficacy against this important insect pest in the field.
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Azizoglu U, Jouzani GS, Yilmaz N, Baz E, Ozkok D. Genetically modified entomopathogenic bacteria, recent developments, benefits and impacts: A review. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 734:139169. [PMID: 32460068 DOI: 10.1016/j.scitotenv.2020.139169] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Revised: 04/10/2020] [Accepted: 04/30/2020] [Indexed: 06/11/2023]
Abstract
Entomopathogenic bacteria (EPBs), insect pathogens that produce pest-specific toxins, are environmentally-friendly alternatives to chemical insecticides. However, the most important problem with EPBs application is their limited field stability. Moreover, environmental factors such as solar radiation, leaf temperature, and vapor pressure can affect the pathogenicity of these pathogens and their toxins. Scientists have conducted intensive research to overcome such problems. Genetic engineering has great potential for the development of new engineered entomopathogens with more resistance to adverse environmental factors. Genetically modified entomopathogenic bacteria (GM-EPBs) have many advantages over wild EPBs, such as higher pathogenicity, lower spraying requirements and longer-term persistence. Genetic manipulations have been mostly applied to members of the bacterial genera Bacillus, Lysinibacillus, Pseudomonas, Serratia, Photorhabdus and Xenorhabdus. Although many researchers have found that GM-EPBs can be used safely as plant protection bioproducts, limited attention has been paid to their potential ecological impacts. The main concerns about GM-EPBs and their products are their potential unintended effects on beneficial insects (predators, parasitoids, pollinators, etc.) and rhizospheric bacteria. This review address recent update on the significant role of GM-EPBs in biological control, examining them through different perspectives in an attempt to generate critical discussion and aid in the understanding of their potential ecological impacts.
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Affiliation(s)
- Ugur Azizoglu
- Department of Crop and Animal Production, Safiye Cikrikcioglu Vocational College, Kayseri University, Kayseri, Turkey.
| | - Gholamreza Salehi Jouzani
- Microbial Biotechnology Department, Agricultural Biotechnology Research Institute of Iran (ABRII), Agricultural Research, Education and Extension Organization (AREEO), Karaj, Iran
| | - Nihat Yilmaz
- Department of Crop and Animal Production, Safiye Cikrikcioglu Vocational College, Kayseri University, Kayseri, Turkey
| | - Ethem Baz
- Laboratory and Veterinary Health Department, Safiye Cikrikcioglu Vocational College, Kayseri University, Kayseri, Turkey
| | - Duran Ozkok
- Department of Crop and Animal Production, Safiye Cikrikcioglu Vocational College, Kayseri University, Kayseri, Turkey
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21
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Heckel DG. How do toxins from Bacillus thuringiensis kill insects? An evolutionary perspective. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2020; 104:e21673. [PMID: 32212396 DOI: 10.1002/arch.21673] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2019] [Revised: 03/11/2020] [Accepted: 03/12/2020] [Indexed: 05/29/2023]
Abstract
Three-domain Cry toxins from the bacterium Bacillus thuringiensis (Bt) are increasingly used in agriculture to replace chemical insecticides in pest control. Most chemical insecticides kill pest insects swiftly, but are also toxic to beneficial insects and other species in the agroecosystem. Cry toxins enjoy the advantages of high selectivity and the possibility of the application by sprays or transgenic plants. However, these benefits are offset by the limited host range and the evolution of resistance to Bt toxins by insect pests. Understanding how Bt toxins kill insects will help to understand the nature of both problems. The recent realization that ABC transporters play a central role in the killing mechanism will play an important role in devising solutions.
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Affiliation(s)
- David G Heckel
- Department of Entomology, Max Planck Institute for Chemical Ecology, Jena, Germany
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22
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Qi L, Qiu X, Yang S, Li R, Wu B, Cao X, He T, Ding X, Xia L, Sun Y. Cry1Ac Protoxin and Its Activated Toxin from Bacillus thuringiensis Act Differentially during the Pathogenic Process. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2020; 68:5816-5824. [PMID: 32379448 DOI: 10.1021/acs.jafc.0c01172] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Although the new dual model of the Bacillus thuringiensis insecticidal mechamism indicated that both Cry1A protoxin and activated toxin have the potency to kill insects, the difference in the toxic pathways elicited by the protoxin and activated toxin was less understood at the molecular level. Through utilizing the CF-203 cell line derived from the midgut of Choristoneura fumiferana, we found that there existed obvious differences in the binding sites and endocytosis pathways for the two forms of Cry1Ac. In addition, it was revealed that Cry1Ac protoxin existed predominantly in the midgut of Plutella xylostella at the early stage after ingesting Cry1Ac crystals, which brought about obvious damage to the midgut epithelium and exhibited different binding sites on the brush border membrane vesicle compared to the toxin. These findings supported the dual mode of action of B. thuringiensis Cry1A proteins and improved our understanding of the molecular features that contribute to the protoxin toxicity.
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Affiliation(s)
- Lingling Qi
- College of Life Science, State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha 410081, People's Republic of China
| | - Xianfeng Qiu
- College of Life Science, State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha 410081, People's Republic of China
| | - Sisi Yang
- College of Life Science, State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha 410081, People's Republic of China
| | - Ran Li
- College of Life Science, State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha 410081, People's Republic of China
| | - Binbin Wu
- College of Life Science, State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha 410081, People's Republic of China
| | - Xiaomei Cao
- College of Life Science, State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha 410081, People's Republic of China
| | - Ting He
- College of Life Science, State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha 410081, People's Republic of China
| | - Xuezhi Ding
- College of Life Science, State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha 410081, People's Republic of China
| | - Liqiu Xia
- College of Life Science, State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha 410081, People's Republic of China
| | - Yunjun Sun
- College of Life Science, State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha 410081, People's Republic of China
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23
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Mackelprang R, Lemaux PG. Genetic Engineering and Editing of Plants: An Analysis of New and Persisting Questions. ANNUAL REVIEW OF PLANT BIOLOGY 2020; 71:659-687. [PMID: 32023090 DOI: 10.1146/annurev-arplant-081519-035916] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Genetic engineering is a molecular biology technique that enables a gene or genes to be inserted into a plant's genome. The first genetically engineered plants were grown commercially in 1996, and the most common genetically engineered traits are herbicide and insect resistance. Questions and concerns have been raised about the effects of these traits on the environment and human health, many of which are addressed in a pair of 2008 and 2009 Annual Review of Plant Biology articles. As new science is published and new techniques like genome editing emerge, reanalysis of some of these issues, and a look at emerging issues, is warranted. Herein, an analysis of relevant scientific literature is used to present a scientific perspective on selected topics related to genetic engineering and genome editing.
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Affiliation(s)
- Rebecca Mackelprang
- Department of Plant and Microbial Biology, University of California, Berkeley, California 94720-3102, USA;
| | - Peggy G Lemaux
- Department of Plant and Microbial Biology, University of California, Berkeley, California 94720-3102, USA;
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24
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Gao M, Hu X, Zhang X, Zhong J, Lu L, Liu Y, Dong S, Wang Y, Liu X. Identification of a Cry1Fa binding site of cadherin in Plutella xylostella through fragment exchanging and molecular docking methods. Int J Biol Macromol 2020; 146:62-69. [PMID: 31836394 DOI: 10.1016/j.ijbiomac.2019.12.063] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Revised: 12/05/2019] [Accepted: 12/08/2019] [Indexed: 11/19/2022]
Abstract
Binding to the cadherin in target pests is the primary step in the action mechanism of Cry toxins, but little is known regarding the interaction of Cry1Fa with cadherin. Our previous study suggested that a Plutella xylostella cadherin fragment (PxCad-TBR) can bind to Cry1Fa, while its homologous fragment (HaCad-TBR) in Helicoverpa armigera cannot. In this study, we expressed two cadherin fragments that combine parts of PxCad-TBR and HaCad-TBR in Escherichia coli and tested their binding to the Cry1Fa. The results showed that the fragment containing amino acids T1202-A1341 of P. xylostella cadherin showed binding ability to Cry1Fa. Furthermore, two regions (V1219-E1233 and D1326-F1337) were predicted as hot spot regions that are involved in the interaction of Cry1Fa and PxCad-TBR with computer-aided molecular docking. We then constructed two PxCad-TBR mutations by fragment exchanging based on the molecular docking results and verified the mutations' binding abilities to the Cry1Fa. The results showed that the region that contains amino acids D1326-F1337 was one important binding site to Cry1Fa in P. xylostella cadherin. These results suggested that a combination of computer-aided molecular docking and fragment exchanging is an effective way to locate the key binding sites of Bt toxins in receptors.
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Affiliation(s)
- Meijing Gao
- Key Lab of Food Quality and Safety of Jiangsu Province-State Key Laboratory Breeding Base, Institute of Food Safety and Nutrition, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China
| | - Xiaodan Hu
- Key Lab of Food Quality and Safety of Jiangsu Province-State Key Laboratory Breeding Base, Institute of Food Safety and Nutrition, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China
| | - Xiao Zhang
- Key Lab of Food Quality and Safety of Jiangsu Province-State Key Laboratory Breeding Base, Institute of Food Safety and Nutrition, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China
| | - Jianfeng Zhong
- Key Lab of Food Quality and Safety of Jiangsu Province-State Key Laboratory Breeding Base, Institute of Food Safety and Nutrition, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China
| | - Lina Lu
- Key Lab of Food Quality and Safety of Jiangsu Province-State Key Laboratory Breeding Base, Institute of Food Safety and Nutrition, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China
| | - Yuan Liu
- Key Lab of Food Quality and Safety of Jiangsu Province-State Key Laboratory Breeding Base, Institute of Food Safety and Nutrition, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China
| | - Sa Dong
- School of Horticulture and Plant Protection, Yangzhou University, China
| | - Yun Wang
- Horticulture Dept, Jinling Institute of Technology, Nanjing, China
| | - Xianjin Liu
- Key Lab of Food Quality and Safety of Jiangsu Province-State Key Laboratory Breeding Base, Institute of Food Safety and Nutrition, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China.
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25
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Khorramnejad A, Domínguez-Arrizabalaga M, Caballero P, Escriche B, Bel Y. Study of the Bacillus thuringiensis Cry1Ia Protein Oligomerization Promoted by Midgut Brush Border Membrane Vesicles of Lepidopteran and Coleopteran Insects, or Cultured Insect Cells. Toxins (Basel) 2020; 12:toxins12020133. [PMID: 32098045 PMCID: PMC7076784 DOI: 10.3390/toxins12020133] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Revised: 01/31/2020] [Accepted: 02/19/2020] [Indexed: 12/18/2022] Open
Abstract
Bacillus thuringiensis (Bt) produces insecticidal proteins that are either secreted during the vegetative growth phase or accumulated in the crystal inclusions (Cry proteins) in the stationary phase. Cry1I proteins share the three domain (3D) structure typical of crystal proteins but are secreted to the media early in the stationary growth phase. In the generally accepted mode of action of 3D Cry proteins (sequential binding model), the formation of an oligomer (tetramer) has been described as a major step, necessary for pore formation and subsequent toxicity. To know if this could be extended to Cry1I proteins, the formation of Cry1Ia oligomers was studied by Western blot, after the incubation of trypsin activated Cry1Ia with insect brush border membrane vesicles (BBMV) or insect cultured cells, using Cry1Ab as control. Our results showed that Cry1Ia oligomers were observed only after incubation with susceptible coleopteran BBMV, but not following incubation with susceptible lepidopteran BBMV or non-susceptible Sf21 insect cells, while Cry1Ab oligomers were persistently detected after incubation with all insect tissues tested, regardless of its host susceptibility. The data suggested oligomerization may not necessarily be a requirement for the toxicity of Cry1I proteins.
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Affiliation(s)
- Ayda Khorramnejad
- Departamento de Genética/ERI BioTecMed, Universitat de València, Burjassot, 46100 València, Spain; (A.K.); (B.E.)
- Department of Plant Protection, College of Agriculture and Natural Resources, University of Tehran, Karaj 31578-77871, Alborz, Iran
| | - Mikel Domínguez-Arrizabalaga
- Departamento de Agronomía, Biotecnología y Alimentación, Universidad Pública de Navarra, Pamplona, 31006 Navarra, Spain; (M.D.-A.); (P.C.)
| | - Primitivo Caballero
- Departamento de Agronomía, Biotecnología y Alimentación, Universidad Pública de Navarra, Pamplona, 31006 Navarra, Spain; (M.D.-A.); (P.C.)
| | - Baltasar Escriche
- Departamento de Genética/ERI BioTecMed, Universitat de València, Burjassot, 46100 València, Spain; (A.K.); (B.E.)
| | - Yolanda Bel
- Departamento de Genética/ERI BioTecMed, Universitat de València, Burjassot, 46100 València, Spain; (A.K.); (B.E.)
- Correspondence:
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26
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Rolim GDS, Plata-Rueda A, Martínez LC, Ribeiro GT, Serrão JE, Zanuncio JC. Side effects of Bacillus thuringiensis on the parasitoid Palmistichus elaeisis (Hymenoptera: Eulophidae). ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2020; 189:109978. [PMID: 31761554 DOI: 10.1016/j.ecoenv.2019.109978] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Revised: 11/12/2019] [Accepted: 11/14/2019] [Indexed: 06/10/2023]
Abstract
The endoparasitoid wasp Palmistichus elaeisis Delvare & LaSalle (Hymenoptera: Eulophidae) is used to control defoliating lepidopteran pests. Chemical insecticides are not compatible with natural enemies, but bioinsecticides, such as Bacillus thuringiensis Berliner (Bt), have great potential for use in integrated pest management. However, interactions between Bt and P. elaeisis still need to be investigated. This study aimed to evaluate the effects of Bt on parental and first-generation P. elaeisis parasitizing Bt-susceptible and -resistant Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae). An additional aim was to determine the toxicity of Bt to susceptible third-instar S. frugiperda larvae. Larvae were exposed to lethal concentrations (LC50 and LC90) of Bt and then allowed to be parasitized by P. elaeisis. Parasitoid longevity, immature production, reproductive performance, and behavioral responses were evaluated. Bt repelled P. elaeisis and reduced immature production. Parental and first filial generation parasitoids of both sexes emerged from Bt-treated larvae showed lower survivorship than controls. Parasitoids had poorer reproductive performance in Bt-susceptible and -resistant pupae than in untreated pupae. Palmistichus elaeisis emerged from Bt-susceptible and -resistant S. frugiperda showed altered host-searching behavior and reproductive parameters, which indicates low compatibility between the bioinsecticide agent and the parasitoid wasp.
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Affiliation(s)
- Gabriela da Silva Rolim
- Departamento de Fitotecnia, Universidade Federal de Viçosa, 36570-900, Viçosa, Minas Gerais, Brazil
| | - Angelica Plata-Rueda
- Instituto de Ciências Agrárias, Universidade Federal de Viçosa, 38810-000, Viçosa, Minas Gerais, Brazil
| | - Luis Carlos Martínez
- Departamento de Biologia Geral, Universidade Federal de Viçosa, 36570-000, Viçosa, Minas Gerais, Brazil.
| | - Genésio Tâmara Ribeiro
- Universidade Federal de Sergipe - Departamento de Ciências Florestais, 49100-000, São Cristóvão, Sergipe, Brazil
| | - José Eduardo Serrão
- Departamento de Biologia Geral, Universidade Federal de Viçosa, 36570-000, Viçosa, Minas Gerais, Brazil
| | - José Cola Zanuncio
- Departamento de Entomologia, Universidade Federal de Viçosa, 36570-000, Viçosa, Minas Gerais, Brazil
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27
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Guo Z, Gong L, Kang S, Zhou J, Sun D, Qin J, Guo L, Zhu L, Bai Y, Bravo A, Soberón M, Zhang Y. Comprehensive analysis of Cry1Ac protoxin activation mediated by midgut proteases in susceptible and resistant Plutella xylostella (L.). PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 2020; 163:23-30. [PMID: 31973862 DOI: 10.1016/j.pestbp.2019.10.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Revised: 09/21/2019] [Accepted: 10/13/2019] [Indexed: 06/10/2023]
Abstract
Insecticidal Cry toxins produced by Bacillus thuringiensis (Bt) have been widely used to control agricultural pests in both foliage sprays and transgenic crops. Nevertheless, rapid evolution of insect resistance to Cry toxins requires elucidation of the molecular mechanisms involved in Cry resistance. Two proposed models have been described to explain the toxicity of Cry proteins, the classic model states that Cry protoxin is activated by midgut proteases resulting in activated toxin that binds to receptors and forms a pore in the midgut cells triggering larval death, and the newly proposed dual model of the mode of action of Bt Cry toxins states that protoxin and activated toxins may have different mechanisms of action since several resistant strains to activated Cry toxins are still susceptible to the same Cry-protoxin. Protoxin activation by midgut proteases is a key step in both models. Herein, we evaluated Cry1Ac protoxin activation in a susceptible Plutella xylostella (L.) strain (DBM1Ac-S) and in the near-isogenic strain (NIL-R) with high field-evolved Cry1Ac resistance. Previous work showed that Cry1Ac resistance in NIL-R correlates with reduced binding to midgut receptors due to enhanced MAPK signaling pathway and down regulation of ABCC2 receptor. However, reduced midgut trypsin levels and altered midgut protease gene transcription were also observed in the Cry1Ac-resistant field isolated strain that is parent of the NIL-R strain. Therefore, we analyzed the midgut protease activities in both DBM1Ac-S and NIL-R strains. Detection of enzymatic activities showed that caseinolytic protease, trypsin and chymotrypsin activities were not significantly different between the susceptible and resistant strains. Furthermore, treatment with different trypsin or chymotrypsin inhibitors, such as Nα-tosyl-l-lysine chloromethyl ketone (TLCK) or Np-tosyl-L-phenylalanine chloromethyl ketone (TPCK) did not affect the susceptibility to Cry1Ac protoxin of the DBM1Ac-S and NIL-R larvae. Bioassay results indicated that the NIL-R larvae showed similar resistant levels to both Cry1Ac protoxin and trypsin-activated toxin. Taken together, our results demonstrated that high-level field-evolved Cry1Ac resistance in the NIL-R strain is independent of Cry1Ac protoxin activation and the specific protoxin mechanism of action. This discovery will strengthen our comprehensive understanding of the complex mechanistic basis of Bt resistance in different insects.
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Affiliation(s)
- Zhaojiang Guo
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
| | - Lijun Gong
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Shi Kang
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Junlei Zhou
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Dan Sun
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Jianying Qin
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Le Guo
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Liuhong Zhu
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Yang Bai
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Alejandra Bravo
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca 62250, Morelos, Mexico
| | - Mario Soberón
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca 62250, Morelos, Mexico
| | - Youjun Zhang
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
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28
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Liu S, Wang S, Wu S, Wu Y, Yang Y. Proteolysis activation of Cry1Ac and Cry2Ab protoxins by larval midgut juice proteases from Helicoverpa armigera. PLoS One 2020; 15:e0228159. [PMID: 32004347 PMCID: PMC6994024 DOI: 10.1371/journal.pone.0228159] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Accepted: 01/08/2020] [Indexed: 12/31/2022] Open
Abstract
Proteolytic processing of Bacillus thuringiensis (Bt) Cry protoxins by insect midgut proteases is critical to their insecticidal activities against target insects. Although transgenic Bt cotton expressing Cry1Ac and Cry2Ab proteins have been widely used for control of the cotton bollworm (Helicoverpa armigera) in the field, the proteolytic cleavage sites in the two protoxins targeted by H. armigera midgut proteases are still not clear. In this study, the proteolysis of Cry1Ac and Cry2Ab protoxins by midgut juice prepared from midgut tissue of H. armigera larvae was investigated. Cleavage of Cry1Ac protoxin by midgut proteases formed a major protein fragment of ~65 kDa, and N-terminal sequencing revealed that cleavage occurred at Arg28 in the fore-end of helix α-1 in domain I of Cry1Ac. Cleavage of Cry2Ab protoxin by midgut juice proteases produced a major protein fragment of ~50 kDa, and the cleavage occurred at Arg139 between helices α-3 and α-4 in domain I of Cry2Ab. The amino acids Arg28 of Cry1Ac and Arg139 of Cry2Ab were predicted as putative trypsin cleavage sites. Bioassay data showed that the toxicities (LC50s) of Cry1Ac and Cry2Ab protoxins were equivalent to those of their respective midgut juice-activated toxins in the susceptible SCD strain of H. armigera. Identification of the exact sites of N-terminal activation of Cry1Ac and Cry2Ab protoxins will provide a basis for a better understanding of the mode of action and resistance mechanisms based on aberrant activation of these protoxins in H. armigera.
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Affiliation(s)
- Shaoyan Liu
- College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Shuo Wang
- College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Shuwen Wu
- College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Yidong Wu
- College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Yihua Yang
- College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu, China
- * E-mail:
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29
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Gong L, Kang S, Zhou J, Sun D, Guo L, Qin J, Zhu L, Bai Y, Ye F, Akami M, Wu Q, Wang S, Xu B, Yang Z, Bravo A, Soberón M, Guo Z, Wen L, Zhang Y. Reduced Expression of a Novel Midgut Trypsin Gene Involved in Protoxin Activation Correlates with Cry1Ac Resistance in a Laboratory-Selected Strain of Plutella xylostella (L.). Toxins (Basel) 2020; 12:toxins12020076. [PMID: 31979385 PMCID: PMC7076802 DOI: 10.3390/toxins12020076] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Revised: 01/18/2020] [Accepted: 01/21/2020] [Indexed: 12/05/2022] Open
Abstract
Bacillus thuringiensis (Bt) produce diverse insecticidal proteins to kill insect pests. Nevertheless, evolution of resistance to Bt toxins hampers the sustainable use of this technology. Previously, we identified down-regulation of a trypsin-like serine protease gene PxTryp_SPc1 in the midgut transcriptome and RNA-Seq data of a laboratory-selected Cry1Ac-resistant Plutella xylostella strain, SZ-R. We show here that reduced PxTryp_SPc1 expression significantly reduced caseinolytic and trypsin protease activities affecting Cry1Ac protoxin activation, thereby conferring higher resistance to Cry1Ac protoxin than activated toxin in SZ-R strain. Herein, the full-length cDNA sequence of PxTryp_SPc1 gene was cloned, and we found that it was mainly expressed in midgut tissue in all larval instars. Subsequently, we confirmed that the PxTryp_SPc1 gene was significantly decreased in SZ-R larval midgut and was further reduced when selected with high dose of Cry1Ac protoxin. Moreover, down-regulation of the PxTryp_SPc1 gene was genetically linked to resistance to Cry1Ac in the SZ-R strain. Finally, RNAi-mediated silencing of PxTryp_SPc1 gene expression decreased larval susceptibility to Cry1Ac protoxin in the susceptible DBM1Ac-S strain, supporting that low expression of PxTryp_SPc1 gene is involved in Cry1Ac resistance in P. xylostella. These findings contribute to understanding the role of midgut proteases in the mechanisms underlying insect resistance to Bt toxins.
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Affiliation(s)
- Lijun Gong
- College of Plant Protection, Hunan Agricultural University, Changsha 410125, China; (L.G.); (L.G.); (F.Y.); (Z.Y.)
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China; (S.K.); (J.Z.); (D.S.); (J.Q.); (L.Z.); (Y.B.); (M.A.); (Q.W.); (S.W.); (B.X.)
| | - Shi Kang
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China; (S.K.); (J.Z.); (D.S.); (J.Q.); (L.Z.); (Y.B.); (M.A.); (Q.W.); (S.W.); (B.X.)
| | - Junlei Zhou
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China; (S.K.); (J.Z.); (D.S.); (J.Q.); (L.Z.); (Y.B.); (M.A.); (Q.W.); (S.W.); (B.X.)
| | - Dan Sun
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China; (S.K.); (J.Z.); (D.S.); (J.Q.); (L.Z.); (Y.B.); (M.A.); (Q.W.); (S.W.); (B.X.)
| | - Le Guo
- College of Plant Protection, Hunan Agricultural University, Changsha 410125, China; (L.G.); (L.G.); (F.Y.); (Z.Y.)
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China; (S.K.); (J.Z.); (D.S.); (J.Q.); (L.Z.); (Y.B.); (M.A.); (Q.W.); (S.W.); (B.X.)
| | - Jianying Qin
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China; (S.K.); (J.Z.); (D.S.); (J.Q.); (L.Z.); (Y.B.); (M.A.); (Q.W.); (S.W.); (B.X.)
| | - Liuhong Zhu
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China; (S.K.); (J.Z.); (D.S.); (J.Q.); (L.Z.); (Y.B.); (M.A.); (Q.W.); (S.W.); (B.X.)
| | - Yang Bai
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China; (S.K.); (J.Z.); (D.S.); (J.Q.); (L.Z.); (Y.B.); (M.A.); (Q.W.); (S.W.); (B.X.)
| | - Fan Ye
- College of Plant Protection, Hunan Agricultural University, Changsha 410125, China; (L.G.); (L.G.); (F.Y.); (Z.Y.)
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China; (S.K.); (J.Z.); (D.S.); (J.Q.); (L.Z.); (Y.B.); (M.A.); (Q.W.); (S.W.); (B.X.)
| | - Mazarin Akami
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China; (S.K.); (J.Z.); (D.S.); (J.Q.); (L.Z.); (Y.B.); (M.A.); (Q.W.); (S.W.); (B.X.)
| | - Qingjun Wu
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China; (S.K.); (J.Z.); (D.S.); (J.Q.); (L.Z.); (Y.B.); (M.A.); (Q.W.); (S.W.); (B.X.)
| | - Shaoli Wang
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China; (S.K.); (J.Z.); (D.S.); (J.Q.); (L.Z.); (Y.B.); (M.A.); (Q.W.); (S.W.); (B.X.)
| | - Baoyun Xu
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China; (S.K.); (J.Z.); (D.S.); (J.Q.); (L.Z.); (Y.B.); (M.A.); (Q.W.); (S.W.); (B.X.)
| | - Zhongxia Yang
- College of Plant Protection, Hunan Agricultural University, Changsha 410125, China; (L.G.); (L.G.); (F.Y.); (Z.Y.)
| | - Alejandra Bravo
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca, Morelos 62250, Mexico; (A.B.); (M.S.)
| | - Mario Soberón
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca, Morelos 62250, Mexico; (A.B.); (M.S.)
| | - Zhaojiang Guo
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China; (S.K.); (J.Z.); (D.S.); (J.Q.); (L.Z.); (Y.B.); (M.A.); (Q.W.); (S.W.); (B.X.)
- Correspondence: (Z.G.); (L.W.); (Y.Z.); Tel.: +86-10-82109518 (Z.G.); +86-0731-84618163 (L.W.); +86-10-62152945 (Y.Z.)
| | - Lizhang Wen
- College of Plant Protection, Hunan Agricultural University, Changsha 410125, China; (L.G.); (L.G.); (F.Y.); (Z.Y.)
- Correspondence: (Z.G.); (L.W.); (Y.Z.); Tel.: +86-10-82109518 (Z.G.); +86-0731-84618163 (L.W.); +86-10-62152945 (Y.Z.)
| | - Youjun Zhang
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China; (S.K.); (J.Z.); (D.S.); (J.Q.); (L.Z.); (Y.B.); (M.A.); (Q.W.); (S.W.); (B.X.)
- Correspondence: (Z.G.); (L.W.); (Y.Z.); Tel.: +86-10-82109518 (Z.G.); +86-0731-84618163 (L.W.); +86-10-62152945 (Y.Z.)
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Insect Hsp90 Chaperone Assists Bacillus thuringiensis Cry Toxicity by Enhancing Protoxin Binding to the Receptor and by Protecting Protoxin from Gut Protease Degradation. mBio 2019; 10:mBio.02775-19. [PMID: 31772047 PMCID: PMC6879724 DOI: 10.1128/mbio.02775-19] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Bacillus thuringiensis took advantage of important insect cellular proteins, such as chaperones, involved in maintaining protein homeostasis, to enhance its insecticidal activity. This constitutes a positive loop where the concentrations of Hsp90 and Hsp70 in the gut lumen are likely to increase as midgut cells burst due to Cry1A pore formation action. Hsp90 protects Cry1A protoxin from degradation and enhances receptor binding, resulting in increased toxicity. The effect of insect chaperones on Cry toxicity could have important biotechnological applications to enhance the toxicity of Cry proteins to insect pests, especially those that show low susceptibility to these toxins. Bacillus thuringiensis Cry proteins are pore-forming insecticidal toxins with specificity against different crop pests and insect vectors of human diseases. Previous work suggested that the insect host Hsp90 chaperone could be involved in Cry toxin action. Here, we show that the interaction of Cry toxins with insect Hsp90 constitutes a positive loop to enhance the performance of these toxins. Plutella xylostella Hsp90 (PxHsp90) greatly enhanced Cry1Ab or Cry1Ac toxicity when fed together to P. xylostella larvae and also in the less susceptible Spodoptera frugiperda larvae. PxHsp90 bound Cry1Ab and Cry1Ac protoxins in an ATP- and chaperone activity-dependent interaction. The chaperone Hsp90 participates in the correct folding of proteins and may suppress mutations of some client proteins, and we show here that PxHsp90 recovered the toxicity of the Cry1AbG439D protoxin affected in receptor binding, in contrast to the Cry1AbR99E or Cry1AbE129K mutant, affected in oligomerization or membrane insertion, respectively, which showed a slight toxicity improvement. Specifically, PxHsp90 enhanced the binding of Cry1AbG439D protoxin to the cadherin receptor. Furthermore, PxHsp90 protected Cry1A protoxins from degradation by insect midgut proteases. Our data show that PxHsp90 assists Cry1A proteins by enhancing their binding to the receptor and by protecting Cry protoxin from gut protease degradation. Finally, we show that the insect cochaperone protein PxHsp70 also increases the toxicity of Cry1Ac in P. xylostella larvae, in contrast to a bacterial GroEL chaperone, which had a marginal effect, indicating that the use of insect chaperones along with Cry toxins could have important biotechnological applications for the improvement of Cry insecticidal activity, resulting in effective control of insect pests.
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31
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West MEJ, Moore PA. Bt Proteins Exacerbate Negative Growth Effects in Juvenile Rusty (F. rusticus) Crayfish Fed Corn Diet. ARCHIVES OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY 2019; 77:452-460. [PMID: 31451889 DOI: 10.1007/s00244-019-00664-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Accepted: 08/17/2019] [Indexed: 06/10/2023]
Abstract
The adoption of genetically modified (GM) crops has occurred rapidly in the United States. The transfer of GM corn byproducts from agricultural fields to nearby streams after harvest is significant and occurs well into the post-harvest year. These corn leaves, stems, and cobs then become a detrital food source for organisms, such as shredders in the stream ecosystem. Considering that the nontarget effects of Bt corn have been observed in some terrestrial organisms, we assessed whether Bt toxins affect an important aquatic organism, juvenile F. rusticus crayfish. Juvenile crayfish were fed six distinct diet treatments: two varieties of Bt corn, two non-Bt controls of herbicide tolerant corn, and two controls: fish gelatin and river detritus. Juveniles were fed these diets while housed in flow-through artificial streams that received natural stream water from a local source. Specific growth rate and survivorship of the crayfish were measured throughout the study. Juveniles fed corn diets grew significantly less and had reduced survival compared with juveniles fed fish gelatin or river detritus diets. Furthermore, juveniles fed one Bt variety of corn (VT Triple Pro®) exhibited significantly less growth than those fed one of the herbicide tolerant varieties (Roundup Ready 2®). Our study shows that corn inputs to streams may be detrimental to the growth and survivorship of juvenile crayfish and that certain Bt varieties may exacerbate these negative effects. These effects on crayfish will have repercussions for the entire ecosystem, because crayfish are conduits of energy between many trophic levels.
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Affiliation(s)
- Molly E J West
- Laboratory for Sensory Ecology, Department of Biological Sciences, Bowling Green State University, Bowling Green, OH, 43403, USA
- University of Michigan Biological Station, Pellston, MI, 49769, USA
| | - Paul A Moore
- Laboratory for Sensory Ecology, Department of Biological Sciences, Bowling Green State University, Bowling Green, OH, 43403, USA.
- University of Michigan Biological Station, Pellston, MI, 49769, USA.
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32
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Synthesis and Characterization of Cry2Ab-AVM Bioconjugate: Enhanced Affinity to Binding Proteins and Insecticidal Activity. Toxins (Basel) 2019; 11:toxins11090497. [PMID: 31461921 PMCID: PMC6783867 DOI: 10.3390/toxins11090497] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Revised: 08/15/2019] [Accepted: 08/15/2019] [Indexed: 12/23/2022] Open
Abstract
Bacillus thuringiensis insecticidal proteins (Bt toxins) have been widely used in crops for agricultural pest management and to reduce the use of chemical insecticides. Here, we have engineered Bt toxin Cry2Ab30 and bioconjugated it with 4"-O-succinyl avermectin (AVM) to synthesize Cry2Ab-AVM bioconjugate. It was found that Cry2Ab-AVM showed higher insecticidal activity against Plutella xylostella, up to 154.4 times compared to Cry2Ab30. The binding results showed that Cry2Ab-AVM binds to the cadherin-like binding protein fragments, the 10th and 11th cadherin repeat domains in the P. xylostella cadherin (PxCR10-11), with a much higher affinity (dissociation equilibrium constant KD = 3.44 nM) than Cry2Ab30 (KD = 28.7 nM). Molecular docking suggested that the macrolide lactone group of Cry2Ab-AVM ligand docking into the PxCR10-11 is a potential mechanism to enhance the binding affinity of Cry2Ab-AVM to PxCR10-11. These findings offer scope for the engineering of Bt toxins by bioconjugation for improved pest management.
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Bacillus thuringiensis Vip1 Functions as a Receptor of Vip2 Toxin for Binary Insecticidal Activity against Holotrichia parallela. Toxins (Basel) 2019; 11:toxins11080440. [PMID: 31349641 PMCID: PMC6723666 DOI: 10.3390/toxins11080440] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Revised: 07/17/2019] [Accepted: 07/24/2019] [Indexed: 11/17/2022] Open
Abstract
Bacillus thuringiensis is a well-known entomopathogenic bacterium that produces vegetative insecticidal proteins (Vips, including Vip1, Vip2, Vip3, and Vip4) during the vegetative phase. Here, we purified Vip1 and Vip2 from B. thuringiensis and characterized the insecticidal effects of these protoxins. Bioassay results showed that a 1:1 mixture of Vip1Ad and Vip2Ag, purified by ion-affinity chromatography independently, exhibited insecticidal activity against Holotrichia parallela larvae, with a 50% lethal concentration value of 2.33 μg/g soil. The brush border membrane (BBM) in the midgut of H. parallela larvae was destroyed after feeding the Vip1Ad and Vip2Ag mixture. Vacuolization of the cytoplasm and slight destruction of BBM were detected with Vip2Ag alone, but not with Vip1Ad alone. Notably, Vip1Ad bound to BBM vesicles (BBMVs) strongly, whereas Vip2Ag showed weak binding; however, binding of Vip2Ag to BBMV was increased when Vip1Ad was added. Ligand blotting showed that Vip2Ag did not bind to Vip1Ad but bound to Vip1Ad-t (Vip1Ad was activated by trypsin), suggesting the activation of Vip1Ad was important for their binary toxicity. Thus, our findings suggested that Vip1Ad may facilitate the binding of Vip2Ag to BBMVs, providing a basis for studies of the insecticidal mechanisms of Vip1Ad and Vip2Ag.
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Lv J, Zhang X, Gao T, Cui T, Peng Q, Zhang J, Song F. Effect of the spoIIID mutation on mother cell lysis in Bacillus thuringiensis. Appl Microbiol Biotechnol 2019; 103:4103-4112. [PMID: 30953122 DOI: 10.1007/s00253-019-09722-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Revised: 02/19/2019] [Accepted: 02/23/2019] [Indexed: 11/28/2022]
Abstract
SpoIIID is a small, sequence-specific DNA-binding protein which can direct many genes' transcription and has an effect on spore formation in Bacillus subtilis. We investigated the role of SpoIIID in mother cell lysis in Bacillus thuringiensis. A β-galactosidase assay based on the promoter fusions with lacZ indicated that the sigK gene was positively regulated by SpoIIID and σK negatively regulated the expression of sigE. The spoIIID mutant strain exhibited no mother cell lysis in Schaeffer's sporulation medium (SSM) but did in ½ Luria-Bertani (LB) medium. cwlC is an essential hydrolase gene for mother cell lysis. Moreover, the expression of a PcwlC-lacZ fusion in spoIIID mutant was proved to be higher in ½ LB medium than in SSM. HD (ΔspoIIID)(ΔcwlC) mutant was obtained by knocking out the cwlC gene in HD(ΔspoIIID) and displayed no mother cell lysis in both SSM and ½ LB mediums. The deletion of spoIIID decreased the crystal protein production in HD73. The expression of Porf1cry8E and P5014 promoter fusions with lacZ gene in the acrystalliferous HD-(ΔspoIIID) mutant showed similar activity to that in the acrystalliferous HD73- strain before T7 and slightly higher than that in the acrystalliferous HD73- after T7. Sodium dodecyl sulfate polyacrylamide gel electrophoresis showed that Cry1Ac production in HD-(ΔspoIIID) directed by the Porf1cry8E and P5014 promoters was at a similar level as that in HD73 wild strain. Altogether, these results suggested that the spoIIID mutant with Porf1cry8E or P5014 promoters could be an alternative delivery system for cry gene expression with no mature spore formation and medium-dependent mother cell lysis.
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Affiliation(s)
- Jing Lv
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
| | - Xin Zhang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
| | - Tantan Gao
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
| | - Tingting Cui
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
| | - Qi Peng
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
| | - Jie Zhang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China
| | - Fuping Song
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China.
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Marques LH, Santos AC, Castro BA, Moscardini VF, Rosseto J, Silva OABN, Babcock JM. Assessing the Efficacy of Bacillus thuringiensis (Bt) Pyramided Proteins Cry1F, Cry1A.105, Cry2Ab2, and Vip3Aa20 Expressed in Bt Maize Against Lepidopteran Pests in Brazil. JOURNAL OF ECONOMIC ENTOMOLOGY 2019; 112:803-811. [PMID: 30561710 PMCID: PMC6427033 DOI: 10.1093/jee/toy380] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Indexed: 05/10/2023]
Abstract
Field studies across four states in maize-producing areas of Brazil were conducted to characterize the efficacy of a new pyramided Bacillus thuringiensis (Bt) Berliner technology in maize, Zea mays L., and compare it to existing single and pyramided commercial Bt technologies, to control Helicoverpa zea Boddie (Lepidoptera: Noctuidae), Elasmopalpus lignosellus Zeller (Lepidoptera: Pyralidae), Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae), and Diatraea saccharalis F. (Lepidoptera: Crambidae). Bt maize expressing Vip3Aa20 protein and pyramided Bt maize expressing proteins Cry1F + Cry1A.105 + Cry2Ab2 + Vip3Aa20 provided excellent protection against kernel feeding by H. zea compared to Bt technologies expressing only Cry1F or Cry1A.105 + Cry2Ab2. Bt maize expressing Cry1F, Cry1A.105 + Cry2Ab2, Cry1F + Cry1A.105 + Cry2Ab2, and Cry1F + Cry1A.105 + Cry2Ab2 + Vip3Aa20 resulted in less than 5% of plants injured by E. lignosellus, significantly less than Bt maize expressing only Vip3Aa20 and a non-Bt maize iso-hybrid with and without a thiamethoxam seed treatment. The highest protection against plant cutting injury caused by A. ipsilon was observed in the pyramid Bt maize technology expressing Cry1F + Cry1A.105 + Cry2Ab2 + Vip3Aa20. However, it did not differ statistically from the Bt maize expressing Vip3Aa20, Cry1F, or Cry1F + Cry1A.105 + Cry2Ab2. All Bt maize hybrids evaluated in our study were highly effective in reducing tunneling injury caused by D. saccharalis. These results show that a new maize technology expressing pyramided Bt proteins Cry1F + Cry1A.105 + Cry2Ab2 + Vip3Aa20 offers a higher level of protection from feeding by the above lepidopteran pest complex compared to maize with a single Bt protein or double pyramided Bt proteins.
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Affiliation(s)
- Luiz H Marques
- Dow AgroSciences Industrial Ltda, Av. Nações Unidas, São Paulo, Brazil
- Corresponding author, e-mail:
| | - Antonio C Santos
- Dow AgroSciences Industrial Ltda, Av. Nações Unidas, São Paulo, Brazil
| | | | | | - Jaedino Rosseto
- Dow AgroSciences Industrial Ltda, Av. Nações Unidas, São Paulo, Brazil
| | - Oscar A B N Silva
- Dow AgroSciences Industrial Ltda, Av. Nações Unidas, São Paulo, Brazil
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36
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Expression of
cry
genes in
Bacillus thuringiensis
biotechnology. Appl Microbiol Biotechnol 2019; 103:1617-1626. [DOI: 10.1007/s00253-018-9552-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2018] [Revised: 11/28/2018] [Accepted: 11/29/2018] [Indexed: 01/03/2023]
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Peña-Cardeña A, Grande R, Sánchez J, Tabashnik BE, Bravo A, Soberón M, Gómez I. The C-terminal protoxin region of Bacillus thuringiensis Cry1Ab toxin has a functional role in binding to GPI-anchored receptors in the insect midgut. J Biol Chem 2018; 293:20263-20272. [PMID: 30385510 PMCID: PMC6311509 DOI: 10.1074/jbc.ra118.005101] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 10/15/2018] [Indexed: 12/20/2022] Open
Abstract
Bacillus thuringiensis Cry toxins are used worldwide for controlling insects. Cry1Ab is produced as a 130-kDa protoxin that is activated by proteolytic removal of an inert 500 amino-acid-long C-terminal region, enabling the activated toxin to bind to insect midgut receptor proteins, leading to its membrane insertion and pore formation. It has been proposed that the C-terminal region is only involved in toxin crystallization, but its role in receptor binding is undefined. Here we show that the C-terminal region of Cry1Ab protoxin provides additional binding sites for alkaline phosphatase (ALP) and aminopeptidase N (APN) insect receptors. ELISA, ligand blot, surface plasmon resonance, and pulldown assays revealed that the Cry1Ab C-terminal region binds to both ALP and APN but not to cadherin. Thus, the C-terminal region provided a higher binding affinity of the protoxin to the gut membrane that correlated with higher toxicity of protoxin than activated toxin. Moreover, Cry1Ab domain II loop 2 or 3 mutations reduced binding of the protoxin to cadherin but not to ALP or APN, supporting the idea that protoxins have additional binding sites. These results imply that two different regions mediate the binding of Cry1Ab protoxin to membrane receptors, one located in domain II-III of the toxin and another in its C-terminal region, suggesting an active role of the C-terminal protoxin fragment in the mode of action of Cry toxins. These results suggest that future manipulations of the C-terminal protoxin region could alter the specificity and increase the toxicity of B. thuringiensis proteins.
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Affiliation(s)
| | - Ricardo Grande
- Unidad de Secuenciación Masiva y Bioinformática, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Avenida Universidad 2001, Colonia Chamilpa, Cuernavaca, Morelos 62210, México and
| | - Jorge Sánchez
- From the Departamento de Microbiología Molecular and
| | - Bruce E Tabashnik
- the Department of Entomology, University of Arizona, Tucson, Arizona 85721
| | | | - Mario Soberón
- From the Departamento de Microbiología Molecular and
| | - Isabel Gómez
- From the Departamento de Microbiología Molecular and.
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An aromatic cluster in Lysinibacillus sphaericus BinB involved in toxicity and proper in-membrane folding. Arch Biochem Biophys 2018; 660:29-35. [PMID: 30321498 DOI: 10.1016/j.abb.2018.10.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Revised: 10/09/2018] [Accepted: 10/11/2018] [Indexed: 12/29/2022]
Abstract
The binary toxin from Lysinibacillus sphaericus has been successfully used for controlling mosquito-transmitted diseases. Based on structural alignments with other toxins, an aromatic cluster in the C-terminal domain of BinB (termed here BC) has been proposed to be important for toxicity. We tested this experimentally using BinB mutants bearing single mutations in this aromatic cluster. Consistent with the hypothesis, two of these mutations, F311A and F315A, were not toxic to Culex quinquefasciatus larvae and were unable to permeabilize liposomes or elicit ion channel activity, in contrast to wild-type BinB. Despite these effects, none of these mutations altered significantly the interaction between the activated forms of the two subunits in solution. These results indicate that these aromatic residues on the C-terminal domain of BinB are critical for toxin insertion in membranes. The latter can be by direct contact of these residues with the membrane surface, or by facilitating the formation a membrane-inserting oligomer.
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Schubert E, Vetter IR, Prumbaum D, Penczek PA, Raunser S. Membrane insertion of α-xenorhabdolysin in near-atomic detail. eLife 2018; 7:38017. [PMID: 30010541 PMCID: PMC6086661 DOI: 10.7554/elife.38017] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Accepted: 07/15/2018] [Indexed: 12/24/2022] Open
Abstract
α-Xenorhabdolysins (Xax) are α-pore-forming toxins (α-PFT) that form 1–1.3 MDa large pore complexes to perforate the host cell membrane. PFTs are used by a variety of bacterial pathogens to attack host cells. Due to the lack of structural information, the molecular mechanism of action of Xax toxins is poorly understood. Here, we report the cryo-EM structure of the XaxAB pore complex from Xenorhabdus nematophila and the crystal structures of the soluble monomers of XaxA and XaxB. The structures reveal that XaxA and XaxB are built similarly and appear as heterodimers in the 12–15 subunits containing pore, classifying XaxAB as bi-component α-PFT. Major conformational changes in XaxB, including the swinging out of an amphipathic helix are responsible for membrane insertion. XaxA acts as an activator and stabilizer for XaxB that forms the actual transmembrane pore. Based on our results, we propose a novel structural model for the mechanism of Xax intoxication. Some bacteria make toxins that punch large holes into the membranes of host cells, destroying them like a puncture destroys a football. These “pore-forming toxins” allow many bacterial species to infect a variety of organisms, from insects to humans. Some sophisticated pore-forming toxins, such as the anthrax toxin, do not only form a pore but also use it to flood lethal toxins into the cell to kill it. One bacterium called Xenorhabdus nematophila punctures the membranes of insect cells, using the same type of pore-forming toxins that other bacteria use to infect humans. Previous research has shown that two proteins – components A and B – form these pore-forming toxins. Given this two-protein formation, some scientists predicted these pore-forming toxins might act like those of the anthrax bacterium: one component forms the pore; the other component poisons the cell. But without detailed images of this pore-forming toxin’s structure, understanding exactly how these two components work together is almost impossible. To explore how components A and B operate within X. nematophila, Schubert et al. captured images of the molecular structure of the two proteins. Common methods reliant on X-rays and electron microscopes revealed the layouts of both components. By visualizing the proteins at different stages, Schubert et al. observed key structural changes that enable them to form the pore and puncture a host cell. Component A binds to component B’s back, forming a subunit – twelve to fifteen of which then conjoin as the pore-forming toxin. Schubert et al. conclude that component A stabilizes each subunit on the membrane and activates component B, which then punctures the membrane by swinging out its lower end. Unlike the anthrax pore-forming toxin, both components collaborate to form the pore complex and puncture the membrane. These results provide a foundation of knowledge about what these toxins look like and how they operate. More research building upon this structural analysis may help scientists develop antibiotics that prevent bacteria from destroying human cells.
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Affiliation(s)
- Evelyn Schubert
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Ingrid R Vetter
- Department of Mechanistic Cell Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Daniel Prumbaum
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Pawel A Penczek
- Department of Biochemistry and Molecular Biology, Houston Medical School, The University of Texas, Houston, United States
| | - Stefan Raunser
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany
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40
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Helix α-3 inter-molecular salt bridges and conformational changes are essential for toxicity of Bacillus thuringiensis 3D-Cry toxin family. Sci Rep 2018; 8:10331. [PMID: 29985464 PMCID: PMC6037675 DOI: 10.1038/s41598-018-28753-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Accepted: 06/29/2018] [Indexed: 12/31/2022] Open
Abstract
Bacillus thuringiensis insecticidal Cry toxins break down larval midgut-cells after forming pores. The 3D-structures of Cry4Ba and Cry5Ba revealed a trimeric-oligomer after cleavage of helices α-1 and α-2a, where helix α-3 is extended and made contacts with adjacent monomers. Molecular dynamic simulations of Cry1Ab-oligomer model based on Cry4Ba-coordinates showed that E101 forms a salt-bridge with R99 from neighbor monomer. An additional salt bridge was identified in the trimeric-Cry5Ba, located at the extended helix α-3 in the region corresponding to the α-2b and α-3 loop. Both salt-bridges were analyzed by site directed mutagenesis. Single-point mutations in the Lepidoptera-specific Cry1Ab and Cry1Fa toxins were affected in toxicity, while reversed double-point mutant partially recovered the phenotype, consistent with a critical role of these salt-bridges. The single-point mutations in the salt-bridge at the extended helix α-3 of the nematicidal Cry5Ba were also non-toxic. The incorporation of this additional salt bridge into the nontoxic Cry1Ab-R99E mutant partially restored oligomerization and toxicity, supporting that the loop between α-2b and α-3 forms part of an extended helix α-3 upon oligomerization of Cry1 toxins. Overall, these results highlight the role in toxicity of salt-bridge formation between helices α-3 of adjacent monomers supporting a conformational change in helix α-3.
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Hu X, Zhang X, Zhong J, Liu Y, Zhang C, Xie Y, Lin M, Xu C, Lu L, Zhu Q, Liu X. Expression of Cry1Ac toxin-binding region in Plutella xyllostella cadherin-like receptor and studying their interaction mode by molecular docking and site-directed mutagenesis. Int J Biol Macromol 2018; 111:822-831. [DOI: 10.1016/j.ijbiomac.2017.12.135] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Revised: 12/15/2017] [Accepted: 12/25/2017] [Indexed: 01/16/2023]
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Xu L, Pan ZZ, Zhang J, Niu LY, Li J, Chen Z, Liu B, Zhu YJ, Chen QX. Exposure of helices α4 and α5 is required for insecticidal activity of Cry2Ab by promoting assembly of a prepore oligomeric structure. Cell Microbiol 2018; 20:e12827. [PMID: 29380507 DOI: 10.1111/cmi.12827] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Revised: 01/15/2018] [Accepted: 01/17/2018] [Indexed: 12/15/2022]
Abstract
Cry2Ab, a pore-forming toxin derived from Bacillus thuringiensis, is widely used as a bio-insecticide to control lepidopteran pests around the world. A previous study revealed that proteolytic activation of Cry2Ab by Plutella xylostella midgut juice was essential for its insecticidal activity against P. xylostella, although the exact molecular mechanism remained unknown. Here, we demonstrated for the first time that proteolysis of Cry2Ab uncovered an active region (the helices α4 and α5 in Domain I), which was required for the mode of action of Cry2Ab. Either the masking or the removal of helices α4 and α5 mediated the pesticidal activity of Cry2Ab. The exposure of helices α4 and α5 did not facilitate the binding of Cry2Ab to P. xylostella midgut receptors but did induce Cry2Ab monomer to aggregate and assemble a 250-kDa prepore oligomer. Site-directed mutagenesis assay was performed to generate Cry2Ab mutants site directed on the helices α4 and α5, and bioassays suggested that some Cry2Ab variants that could not form oligomers had significantly lowered their toxicities against P. xylostella. Taken together, our data highlight the importance of helices α4 and α5 in the mode of action of Cry2Ab and could lead to more detailed studies on the insecticidal activity of Cry2Ab.
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Affiliation(s)
- Lian Xu
- State Key Laboratory of Cellular Stress Biology, Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, School of Life Sciences, Xiamen University, Xiamen, Fujian, People's Republic of China
| | - Zhi-Zhen Pan
- Agricultural Bio-Resources Research Institute, Fujian Academy of Agricultural Sciences, Fuzhou, Fujian, People's Republic of China
| | - Jing Zhang
- State Key Laboratory of Cellular Stress Biology, Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, School of Life Sciences, Xiamen University, Xiamen, Fujian, People's Republic of China
| | - Li-Yang Niu
- State Key Laboratory of Cellular Stress Biology, Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, School of Life Sciences, Xiamen University, Xiamen, Fujian, People's Republic of China
| | - Jie Li
- State Key Laboratory of Cellular Stress Biology, Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, School of Life Sciences, Xiamen University, Xiamen, Fujian, People's Republic of China
| | - Zheng Chen
- Agricultural Bio-Resources Research Institute, Fujian Academy of Agricultural Sciences, Fuzhou, Fujian, People's Republic of China
| | - Bo Liu
- Agricultural Bio-Resources Research Institute, Fujian Academy of Agricultural Sciences, Fuzhou, Fujian, People's Republic of China
| | - Yu-Jing Zhu
- Agricultural Bio-Resources Research Institute, Fujian Academy of Agricultural Sciences, Fuzhou, Fujian, People's Republic of China
| | - Qing-Xi Chen
- State Key Laboratory of Cellular Stress Biology, Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, School of Life Sciences, Xiamen University, Xiamen, Fujian, People's Republic of China
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Li X, Zhao F, Qiu X, Ren X, Mo X, Ding X, Xia L, Sun Y. The full-length Cry1Ac protoxin without proteolytic activation exhibits toxicity against insect cell line CF-203. J Invertebr Pathol 2018; 152:25-29. [PMID: 29408155 DOI: 10.1016/j.jip.2018.01.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Revised: 01/06/2018] [Accepted: 01/17/2018] [Indexed: 11/19/2022]
Abstract
The new dual model for Bacillus thuringiensis insecticidal mechanism proposed that Cry1A protoxins without proteolytic activation could bind to insect midgut receptors to exert toxicity. To evaluate insecticidal potency of Cry1Ac protoxin at precluding interference of midgut proteases, the cytotoxicity of Cry1Ac protoxin against midgut cell line CF-203 derived from Choristoneura fumiferana was analyzed. It was revealed that Cry1Ac protoxin was toxic to CF-203 cells and there existed certain differences in the cytological changes when treated with protoxin and toxin. Our cell-based study provided direct evidence for the proposed dual model and shed light on exploring the difference between two toxic pathways elicited by intact protoxin and activated toxin.
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Affiliation(s)
- Xiaodi Li
- College of Life Science, State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha 410081, PR China
| | - Feng Zhao
- College of Life Science, State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha 410081, PR China
| | - Xianfeng Qiu
- College of Life Science, State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha 410081, PR China
| | - Xiaomeng Ren
- College of Life Science, State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha 410081, PR China
| | - Xiangtao Mo
- College of Life Science, State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha 410081, PR China
| | - Xuezhi Ding
- College of Life Science, State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha 410081, PR China
| | - Liqiu Xia
- College of Life Science, State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha 410081, PR China
| | - Yunjun Sun
- College of Life Science, State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha 410081, PR China.
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Soberón M, Portugal L, Garcia-Gómez BI, Sánchez J, Onofre J, Gómez I, Pacheco S, Bravo A. Cell lines as models for the study of Cry toxins from Bacillus thuringiensis. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2018; 93:66-78. [PMID: 29269111 DOI: 10.1016/j.ibmb.2017.12.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Revised: 12/15/2017] [Accepted: 12/16/2017] [Indexed: 06/07/2023]
Abstract
Cell lines have been use extensively for the study of the mode of action of different pore forming toxins produced by different bacterial species. Bacillus thuringiensis Cry toxins are not the exception and their mechanism of action has been analyzed in different cell lines. Here we review the data obtained with different cell lines, including those that are naturally susceptible to the three domain Cry toxins (3d-Cry) and other non-susceptible cell lines that have been transformed with 3d-Cry toxin binding molecules cloned from the susceptible insects. The effects on Cry toxin action after expressing different insect gut proteins, such as glycosyl-phosphatidyl-inositol (GPI) anchored proteins (like alkaline phosphatase (ALP) aminopeptidase (APN)), or trans-membrane proteins (like cadherin (CAD) or ATP-binding cassette subfamily C member 2 (ABCC2) transporter) in cell lines showed that, with few exceptions, expression of GPI-anchored proteins do not correlated with increased susceptibility to the toxin, while the expression of CAD or ABCC2 proteins correlated with induced susceptibility to Cry toxins in the transformed cells lines. Also, that the co-expression of CAD and ABCC2 transporter induced a synergistic effect in the toxicity of 3d-Cry toxins. Overall the data show that in susceptible cell lines, the 3d-Cry toxins induce pore formation that correlates with toxicity. However, the intracellular responses remain controversial since it was shown that the same 3d-Cry toxin in different cell lines activated different responses such as adenylate cyclase-PKA death response or apoptosis. Parasporins are Cry toxins that are toxic to cancer cell lines that have structural similarities with the insecticidal Cry toxins. They belong to the 3d-Cry toxin or to MTX-like Cry toxin families but also show important differences with the insecticidal Cry proteins. Some parasporins are pore-forming toxins, and some activate apoptosis. In this review we summarized the results of the different studies about the Cry toxins mode of action using cultured cell lines and discuss their relation with the studies performed in insect larvae.
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Affiliation(s)
- Mario Soberón
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca 62250, Morelos, Mexico.
| | - Leivi Portugal
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca 62250, Morelos, Mexico.
| | - Blanca-Ines Garcia-Gómez
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca 62250, Morelos, Mexico.
| | - Jorge Sánchez
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca 62250, Morelos, Mexico
| | - Janette Onofre
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca 62250, Morelos, Mexico
| | - Isabel Gómez
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca 62250, Morelos, Mexico.
| | - Sabino Pacheco
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca 62250, Morelos, Mexico.
| | - Alejandra Bravo
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca 62250, Morelos, Mexico.
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Soberón M, Monnerat R, Bravo A. Mode of Action of Cry Toxins from Bacillus thuringiensis and Resistance Mechanisms. TOXINOLOGY 2018. [DOI: 10.1007/978-94-007-6449-1_28] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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Zhang L, Zhao G, Hu X, Liu J, Li M, Batool K, Chen M, Wang J, Xu J, Huang T, Pan X, Xu L, Yu XQ, Guan X. Cry11Aa Interacts with the ATP-Binding Protein from Culex quinquefasciatus To Improve the Toxicity. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2017; 65:10884-10890. [PMID: 29215274 DOI: 10.1021/acs.jafc.7b04427] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Cry11Aa displays high toxicity to the larvae of several mosquito species, including Aedes, Culex, and Anopheles. To study its binding characterization against Culex quinquefasciatus, Cry11Aa was purified and western blot results showed that Cry11Aa could bind successfully to the brush border membrane vesicles. To identify Cry11Aa-binding proteins in C. quinquefasciatus, a biotin-based protein pull-down experiment was performed and seven Cry11Aa-binding proteins were isolated from the midgut of C. quinquefasciatus larvae. Analysis of liquid chromatography-tandem mass spectrometry showed that one of the Cry11Aa-binding proteins is the ATP-binding domain 1 family member B. To investigate its binding property and effect on the toxicity of Cry11Aa, western blot, far-western blot, enzyme-linked immunosorbent assay, and bioassays of Cry11Aa in the presence and absence of the recombinant ATP-binding protein were performed. Our results showed that the ATP-binding protein interacted with Cry11Aa and increased the toxicity of Cry11Aa against C. quinquefasciatus. Our study suggests that midgut proteins other than the toxin receptors may modulate the toxicity of Cry toxins against mosquitoes.
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Affiliation(s)
- Lingling Zhang
- Division of Cell Biology and Biophysics, University of Missouri-Kansas City , Kansas City, Missouri 64110, United States
| | | | | | | | | | | | | | | | | | | | | | | | - Xiao-Qiang Yu
- Division of Cell Biology and Biophysics, University of Missouri-Kansas City , Kansas City, Missouri 64110, United States
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Onofre J, Gaytán MO, Peña-Cardeña A, García-Gomez BI, Pacheco S, Gómez I, Bravo A, Soberón M. Identification of Aminopeptidase-N2 as a Cry2Ab binding protein in Manduca sexta. Peptides 2017; 98:93-98. [PMID: 28108197 DOI: 10.1016/j.peptides.2017.01.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Revised: 01/06/2017] [Accepted: 01/09/2017] [Indexed: 11/15/2022]
Abstract
Bacillus thuringiensis Cry2Ab toxin has been used in combination with Cry1Ac for resistance management on the Bt-cotton that is widely planted worldwide. However, little is known regarding Cry2Ab mode of action. Particularly, there is a gap of knowledge on the identification of insect midgut proteins that bind Cry2Ab and mediate toxicity. In the case of Cry1Ab toxin, a transmembrane cadherin protein and glycosyl-phosphatidylinositol (GPI) anchored proteins like aminopeptidase-N1 (APN1) or alkaline-phosphatase (ALP) from Manduca sexta, have been shown to be important for oligomer formation and insertion into the membrane. Binding competition experiments showed that Cry2Ab toxin does not share binding sites with Cry1Ab toxin in M. sexta brush border membrane vesicles (BBMV). Also, that Cry2Ab shows reduced binding to the Cry1Ab binding molecules cadherin, APN1 or ALP. Finally, ligand blot experiments and protein sequence by LC-MS/MS identified APN2 isoform as a Cry2Ab binding protein. Cloning and expression of APN2 confirmed that APN2 is a Cry2Ab binding protein.
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Affiliation(s)
- Janette Onofre
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo, Postal 510-3, Cuernavaca 62250, Morelos, Mexico
| | - Meztlli O Gaytán
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo, Postal 510-3, Cuernavaca 62250, Morelos, Mexico
| | - Arlen Peña-Cardeña
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo, Postal 510-3, Cuernavaca 62250, Morelos, Mexico
| | - Blanca I García-Gomez
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo, Postal 510-3, Cuernavaca 62250, Morelos, Mexico
| | - Sabino Pacheco
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo, Postal 510-3, Cuernavaca 62250, Morelos, Mexico
| | - Isabel Gómez
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo, Postal 510-3, Cuernavaca 62250, Morelos, Mexico
| | - Alejandra Bravo
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo, Postal 510-3, Cuernavaca 62250, Morelos, Mexico
| | - Mario Soberón
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo, Postal 510-3, Cuernavaca 62250, Morelos, Mexico.
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Martínez de Castro DL, García-Gómez BI, Gómez I, Bravo A, Soberón M. Identification of Bacillus thuringiensis Cry1AbMod binding-proteins from Spodoptera frugiperda. Peptides 2017; 98:99-105. [PMID: 28958733 DOI: 10.1016/j.peptides.2017.09.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Revised: 09/06/2017] [Accepted: 09/22/2017] [Indexed: 12/12/2022]
Abstract
Bacillus thuringiensis Cry toxins are currently used for pest control in transgenic crops but evolution of resistance by the insect pests threatens the use of this technology. The Cry1AbMod toxin was engineered to lack the alpha helix-1 of the parental Cry1Ab toxin and was shown to counter resistance to Cry1Ab and Cry1Ac toxins in different insect species including the fall armyworm Spodoptera frugiperda. In addition, Cry1AbMod showed enhanced toxicity to Cry1Ab-susceptible S. frugiperda populations. To gain insights into the mechanisms of this Cry1AbMod-enhanced toxicity, we isolated the Cry1AbMod toxin binding proteins from S. frugiperda brush border membrane vesicles (BBMV), which were identified by pull-down assay and liquid chromatography-tandem mass spectrometry (LC-MS/MS). The LC-MS/MS results indicated that Cry1AbMod toxin could bind to four classes of aminopeptidase (N1, N3, N4 y N5) and actin, with the highest amino acid sequence coverage acquired for APN 1 and APN4. In addition to these proteins, we found other proteins not previously described as Cry toxin binding proteins. This is the first report that suggests the interaction between Cry1AbMod and APN in S. frugiperda.
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Affiliation(s)
- Diana L Martínez de Castro
- Instituto de Biotecnología, Universidad Nacional Autónoma de México. Apdo. Postal 510-3, Cuernavaca, 62250 Morelos, Mexico
| | - Blanca I García-Gómez
- Instituto de Biotecnología, Universidad Nacional Autónoma de México. Apdo. Postal 510-3, Cuernavaca, 62250 Morelos, Mexico
| | - Isabel Gómez
- Instituto de Biotecnología, Universidad Nacional Autónoma de México. Apdo. Postal 510-3, Cuernavaca, 62250 Morelos, Mexico
| | - Alejandra Bravo
- Instituto de Biotecnología, Universidad Nacional Autónoma de México. Apdo. Postal 510-3, Cuernavaca, 62250 Morelos, Mexico
| | - Mario Soberón
- Instituto de Biotecnología, Universidad Nacional Autónoma de México. Apdo. Postal 510-3, Cuernavaca, 62250 Morelos, Mexico.
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An Intramolecular Salt Bridge in Bacillus thuringiensis Cry4Ba Toxin Is Involved in the Stability of Helix α-3, Which Is Needed for Oligomerization and Insecticidal Activity. Appl Environ Microbiol 2017; 83:AEM.01515-17. [PMID: 28802270 DOI: 10.1128/aem.01515-17] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Accepted: 08/04/2017] [Indexed: 01/30/2023] Open
Abstract
Bacillus thuringiensis three-domain Cry toxins kill insects by forming pores in the apical membrane of larval midgut cells. Oligomerization of the toxin is an important step for pore formation. Domain I helix α-3 participates in toxin oligomerization. Here we identify an intramolecular salt bridge within helix α-3 of Cry4Ba (D111-K115) that is conserved in many members of the family of three-domain Cry toxins. Single point mutations such as D111K or K115D resulted in proteins severely affected in toxicity. These mutants were also altered in oligomerization, and the mutant K115D was more sensitive to protease digestion. The double point mutant with reversed charges, D111K-K115D, recovered both oligomerization and toxicity, suggesting that this salt bridge is highly important for conservation of the structure of helix α-3 and necessary to promote the correct oligomerization of the toxin.IMPORTANCE Domain I has been shown to be involved in oligomerization through helix α-3 in different Cry toxins, and mutations affecting oligomerization also elicit changes in toxicity. The three-dimensional structure of the Cry4Ba toxin reveals an intramolecular salt bridge in helix α-3 of domain I. Mutations that disrupt this salt bridge resulted in changes in Cry4Ba oligomerization and toxicity, while a double point reciprocal mutation that restored the salt bridge resulted in recovery of toxin oligomerization and toxicity. These data highlight the role of oligomer formation as a key step in Cry4Ba toxicity.
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ABCC2 is associated with Bacillus thuringiensis Cry1Ac toxin oligomerization and membrane insertion in diamondback moth. Sci Rep 2017; 7:2386. [PMID: 28539590 PMCID: PMC5443830 DOI: 10.1038/s41598-017-02545-y] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 04/12/2017] [Indexed: 12/19/2022] Open
Abstract
Cry1A insecticidal toxins bind sequentially to different larval gut proteins facilitating oligomerization, membrane insertion and pore formation. Cry1Ac interaction with cadherin triggers oligomerization. However, a mutation in an ABC transporter gene (ABCC2) is linked to Cry1Ac resistance in Plutella xylostella. Cry1AcMod, engineered to lack helix α-1, was able to form oligomers without cadherinbinding and effectively countered Cry1Ac resistance linked to ABCC2. Here we analyzed Cry1Ac and Cry1AcMod binding and oligomerization by western blots using brush border membrane vesicles (BBMV) from a strain of P. xylostella susceptible to Cry1Ac (Geneva 88) and a strain with resistance to Cry1Ac (NO-QAGE) linked to an ABCC2 mutation. Resistance correlated with lack of specific binding and reduced oligomerization of Cry1Ac in BBMV from NO-QAGE. In contrast, Cry1AcMod bound specifically and still formed oligomers in BBMV from both strains. We compared association of pre-formed Cry1Ac oligomer, obtained by incubating Cry1Ac toxin with a Manduca sexta cadherin fragment, with BBMV from both strains. Our results show that pre-formed oligomers associate more efficiently with BBMV from Geneva 88 than with BBMV from NO-QAGE, indicating that the ABCC2 mutation also affects the association of Cry1Ac oligomer with the membrane. These data indicate, for the first time, that ABCC2 facilitates Cry1Ac oligomerization and oligomer membrane insertion in P. xylostella.
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