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Dutta TK, Santhoshkumar K, Veeresh A, Waghmare C, Mathur C, Sreevathsa R. RNAi-based knockdown of candidate gut receptor genes altered the susceptibility of Spodoptera frugiperda and S. litura larvae to a chimeric toxin Cry1AcF. PeerJ 2023; 11:e14716. [PMID: 36710863 PMCID: PMC9881468 DOI: 10.7717/peerj.14716] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 12/19/2022] [Indexed: 01/25/2023] Open
Abstract
Background A multitude of Cry toxins (secreted by Bacillus thuringiensis or Bt) has been deployed globally either via transgenic mean or bio-pesticidal formulations in order to manage insect pests. However, Bt resistance development in insects is emerging as a major concern. To avoid this problem, multiple gene pyramiding or protein-engineered chimeric toxin-based strategy has been analyzed. Methods In the present study, one such chimeric toxin Cry1AcF (contain the swapped domains of Cry1Ac and Cry1F) was used to investigate its in vivo pathogenesis process in lepidopteran pests Spodoptera frugiperda and S. litura. A number of biochemical and molecular analysis were performed. Results Oral ingestion of Cry1AcF caused greater toxicity in S. frugiperda than S. litura with larvae displaying increased hemolymph melanization. Histopathology of the midgut transverse sections exhibited Cry1AcF-induced extensive gut damage in both the test insects followed by cytotoxicity in terms of reduced hemocyte numbers and viability. Elevated hemolymph phenoloxidase activity indicated the immune-stimulatory nature of Cry1AcF. In order to analyze the role of gut receptor proteins in Cry1AcF intoxication in test insects, we performed RNAi-mediated silencing using bacterially-expressed dsRNAs of individual receptor-encoding genes including CAD, ABCC2, ALP1 and APN. Target-specific induced downregulation of receptor mRNAs differentially altered the insect susceptibility to Cry1AcF toxin in our study. The susceptibility of ALP1 and APN dsRNA pre-treated S. frugiperda was considerably decreased when treated with Cry1AcF in LD50 and LD90 doses, whereas susceptibility of CAD and ABCC2 dsRNA pre-treated S. litura was significantly reduced when ingested with Cry1AcF in different doses. CAD/ABCC2-silenced S. frugiperda and ALP1/APN-silenced S. litura were vulnerable to Cry1AcF alike of control larvae. In conclusion, our results indicate ALP1/APN and CAD/ABCC2 as the functional receptor for Cry1AcF toxicity in S. frugiperda and S. litura, respectively.
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Affiliation(s)
- Tushar K. Dutta
- Division of Nematology, ICAR-Indian Agricultural Research Institute, New Delhi, Delhi, India
| | | | - Arudhimath Veeresh
- Division of Nematology, ICAR-Indian Agricultural Research Institute, New Delhi, Delhi, India
| | - Chandramani Waghmare
- Division of Nematology, ICAR-Indian Agricultural Research Institute, New Delhi, Delhi, India
| | - Chetna Mathur
- Division of Nematology, ICAR-Indian Agricultural Research Institute, New Delhi, Delhi, India
| | - Rohini Sreevathsa
- ICAR-National Institute for Plant Biotechnology, New Delhi, Delhi, India
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Díaz-Valerio S, Lev Hacohen A, Schöppe R, Liesegang H. IDOPS, a Profile HMM-Based Tool to Detect Pesticidal Sequences and Compare Their Genetic Context. Front Microbiol 2021; 12:664476. [PMID: 34276598 PMCID: PMC8279765 DOI: 10.3389/fmicb.2021.664476] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Accepted: 05/13/2021] [Indexed: 11/13/2022] Open
Abstract
Biopesticide-based crop protection is constantly challenged by insect resistance. Thus, expansion of available biopesticides is crucial for sustainable agriculture. Although Bacillus thuringiensis is the major agent for pesticide bioprotection, the number of bacteria species synthesizing proteins with biopesticidal potential is much higher. The Bacterial Pesticidal Protein Resource Center (BPPRC) offers a database of sequences for the control of insect pests, grouped in structural classes. Here we present IDOPS, a tool that detects novel biopesticidal sequences and analyzes them within their genetic environment. The backbone of the IDOPS detection unit is a curated collection of high-quality hidden Markov models that is in accordance with the BPPRC nomenclature. IDOPS was positively benchmarked with BtToxin_Digger and Cry_Processor. In addition, a scan of the UniProtKB database using the IDOPS models returned an abundance of new pesticidal protein candidates distributed across all of the structural groups. Gene expression depends on the genomic environment, therefore, IDOPS provides a comparative genomics module to investigate the genetic regions surrounding pesticidal genes. This feature enables the investigation of accessory elements and evolutionary traits relevant for optimal toxin expression and functional diversification. IDOPS contributes and expands our current arsenal of pesticidal proteins used for crop protection.
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Affiliation(s)
- Stefani Díaz-Valerio
- Genomic and Applied Microbiology & Göttingen Genomics Laboratory, Institute of Microbiology and Genetics, Georg-August University of Göttingen, Göttingen, Germany
| | - Anat Lev Hacohen
- Genomic and Applied Microbiology & Göttingen Genomics Laboratory, Institute of Microbiology and Genetics, Georg-August University of Göttingen, Göttingen, Germany
| | - Raphael Schöppe
- Genomic and Applied Microbiology & Göttingen Genomics Laboratory, Institute of Microbiology and Genetics, Georg-August University of Göttingen, Göttingen, Germany
| | - Heiko Liesegang
- Genomic and Applied Microbiology & Göttingen Genomics Laboratory, Institute of Microbiology and Genetics, Georg-August University of Göttingen, Göttingen, Germany
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Karthik K, Negi J, Rathinam M, Saini N, Sreevathsa R. Exploitation of Novel Bt ICPs for the Management of Helicoverpa armigera (Hübner) in Cotton ( Gossypium hirsutum L.): A Transgenic Approach. Front Microbiol 2021; 12:661212. [PMID: 33995323 PMCID: PMC8116509 DOI: 10.3389/fmicb.2021.661212] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2021] [Accepted: 03/18/2021] [Indexed: 12/02/2022] Open
Abstract
Cotton is a commercial crop of global importance. The major threat challenging the productivity in cotton has been the lepidopteron insect pest Helicoverpa armigera or cotton bollworm which voraciously feeds on various plant parts. Biotechnological interventions to manage this herbivore have been a universally inevitable option. The advent of plant genetic engineering and exploitation of Bacillus thuringiensis (Bt) insecticidal crystal proteins (ICPs) marked the beginning of plant protection in cotton through transgenic technology. Despite phenomenal success and widespread acceptance, the fear of resistance development in insects has been a perennial concern. To address this issue, alternate strategies like introgression of a combination of cry protein genes and protein-engineered chimeric toxin genes came into practice. The utility of chimeric toxins produced by domain swapping, rearrangement of domains, and other strategies aid in toxins emerging with broad spectrum efficacy that facilitate the avoidance of resistance in insects toward cry toxins. The present study demonstrates the utility of two Bt ICPs, cry1AcF (produced by domain swapping) and cry2Aa (produced by codon modification) in transgenic cotton for the mitigation of H. armigera. Transgenics were developed in cotton cv. Pusa 8–6 by the exploitation of an apical meristem-targeted in planta transformation protocol. Stringent trait efficacy-based selective screening of T1 and T2 generation transgenic plants enabled the identification of plants resistant to H. armigera upon deliberate challenging. Evaluation of shortlisted events in T3 generation identified a total of nine superior transgenic events with both the genes (six with cry1AcF and three with cry2Aa). The transgenic plants depicted 80–100% larval mortality of H. armigera and 10–30% leaf damage. Molecular characterization of the shortlisted transgenics demonstrated stable integration, inheritance and expression of transgenes. The study is the first of its kind to utilise a non-tissue culture-based transformation strategy for the development of stable transgenics in cotton harbouring two novel genes, cry1AcF and cry2Aa for insect resistance. The identified transgenic events can be potential options toward the exploitation of unique cry genes for the management of the polyphagous insect pest H. armigera.
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Affiliation(s)
- Kesiraju Karthik
- ICAR-National Institute for Plant Biotechnology, New Delhi, India
| | - Jyotsana Negi
- ICAR-National Institute for Plant Biotechnology, New Delhi, India
| | - Maniraj Rathinam
- ICAR-National Institute for Plant Biotechnology, New Delhi, India
| | - Navinder Saini
- Division of Genetics, ICAR-Indian Agricultural Research Institute, New Delhi, India
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Vílchez S. Making 3D-Cry Toxin Mutants: Much More Than a Tool of Understanding Toxins Mechanism of Action. Toxins (Basel) 2020; 12:toxins12090600. [PMID: 32948025 PMCID: PMC7551160 DOI: 10.3390/toxins12090600] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 08/15/2020] [Accepted: 08/20/2020] [Indexed: 12/21/2022] Open
Abstract
3D-Cry toxins, produced by the entomopathogenic bacterium Bacillus thuringiensis, have been extensively mutated in order to elucidate their elegant and complex mechanism of action necessary to kill susceptible insects. Together with the study of the resistant insects, 3D-Cry toxin mutants represent one of the pillars to understanding how these toxins exert their activity on their host. The principle is simple, if an amino acid is involved and essential in the mechanism of action, when substituted, the activity of the toxin will be diminished. However, some of the constructed 3D-Cry toxin mutants have shown an enhanced activity against their target insects compared to the parental toxins, suggesting that it is possible to produce novel versions of the natural toxins with an improved performance in the laboratory. In this report, all mutants with an enhanced activity obtained by accident in mutagenesis studies, together with all the variants obtained by rational design or by directed mutagenesis, were compiled. A description of the improved mutants was made considering their historical context and the parallel development of the protein engineering techniques that have been used to obtain them. This report demonstrates that artificial 3D-Cry toxins made in laboratories are a real alternative to natural toxins.
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Affiliation(s)
- Susana Vílchez
- Institute of Biotechnology, Department of Biochemistry and Molecular Biology I, Faculty of Science, University of Granada, 18071 Granada, Spain
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Rathinam M, Kesiraju K, Singh S, Thimmegowda V, Rai V, Pattanayak D, Sreevathsa R. Molecular Interaction-Based Exploration of the Broad Spectrum Efficacy of a Bacillus thuringiensis Insecticidal Chimeric Protein, Cry1AcF. Toxins (Basel) 2019; 11:toxins11030143. [PMID: 30832332 PMCID: PMC6468889 DOI: 10.3390/toxins11030143] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2018] [Revised: 02/04/2019] [Accepted: 02/06/2019] [Indexed: 11/16/2022] Open
Abstract
Bacillus thuringiensis insecticidal proteins (Bt ICPs) are reliable and valuable options for pest management in crops. Protein engineering of Bt ICPs is a competitive alternative for resistance management in insects. The primary focus of the study was to reiterate the translational utility of a protein-engineered chimeric Cry toxin, Cry1AcF, for its broad spectrum insecticidal efficacy using molecular modeling and docking studies. In-depth bioinformatic analysis was undertaken for structure prediction of the Cry toxin as the ligand and aminopeptidase1 receptors (APN1) from Helicoverpa armigera (HaAPN1) and Spodoptera litura (SlAPN1) as receptors, followed by interaction studies using protein-protein docking tools. The study revealed feasible interactions between the toxin and the two receptors through H-bonding and hydrophobic interactions. Further, molecular dynamics simulations substantiated the stability of the interactions, proving the broad spectrum efficacy of Cry1AcF in controlling H. armigera and S. litura. These findings justify the utility of protein-engineered toxins in pest management.
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Affiliation(s)
- Maniraj Rathinam
- ICAR-National Research Centre on Plant Biotechnology, New Delhi 110012, India.
| | - Karthik Kesiraju
- ICAR-National Research Centre on Plant Biotechnology, New Delhi 110012, India.
| | - Shweta Singh
- ICAR-National Research Centre on Plant Biotechnology, New Delhi 110012, India.
| | - Vinutha Thimmegowda
- Division of Biochemistry, ICAR-Indian Agricultural Research Institute, New Delhi 110012, India.
| | - Vandna Rai
- ICAR-National Research Centre on Plant Biotechnology, New Delhi 110012, India.
| | - Debasis Pattanayak
- ICAR-National Research Centre on Plant Biotechnology, New Delhi 110012, India.
| | - Rohini Sreevathsa
- ICAR-National Research Centre on Plant Biotechnology, New Delhi 110012, India.
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Qiu X, Lu X, Ren X, Li R, Wu B, Yang S, Qi L, Mo X, Ding X, Xia L, Sun Y. Solubility enhancement of Cry2Aa crystal through carboxy-terminal extension and synergism between the chimeric protein and Cry1Ac. Appl Microbiol Biotechnol 2019; 103:2243-2250. [PMID: 30617818 DOI: 10.1007/s00253-018-09606-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Revised: 12/26/2018] [Accepted: 12/28/2018] [Indexed: 11/26/2022]
Abstract
It was reported that the highly conserved C-terminal region of Bacillus thuringiensis Cry1A protoxins was very important for parasporal crystal formation and solubility feature in alkaline environment. In order to improve the solubilization efficiency of Cry2Aa crystal, the coding sequences of Cry2Aa protein and the C-terminal half of Cry1Ac were fused seamlessly through Red/ET homologous recombination and expressed in an acrystalliferous B. thuringiensis strain under the control of the cry1Ac promoter and terminator. Microscopic observation revealed that the recombinant strain containing the chimeric gene cry2Aa-1Ac produced distinct parasporal inclusion with semispherical to approximately cuboidal shape during sporulation. SDS-PAGE analysis showed that this strain expressed stable 130-kDa Cry2Aa-1Ac chimeric protein, which was confirmed to be the correctly expressed product by LC-MS/MS. The chimeric protein inclusion could be effectively dissolved at pH 10.5 and activated by trypsin like the parental Cry1Ac crystal. While, the parental Cry2Aa crystal exhibited very low solubility under this condition. Bioassays against third-instar larvae of Helicoverpa armigera proved that the chimeric protein was more toxic than Cry2Aa. Additionally, synergistic effect was clearly detected between the chimeric protein and Cry1Ac against H. armigera, while there was only additive effect for the combination of wild Cry2Aa and Cry1Ac. These results indicated that the developed chimeric protein might serve as a potent insecticidal toxin used in the field against lepidopteran pests.
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Affiliation(s)
- 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
| | - Xiuqing Lu
- College of Life Science, State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha, 410081, People's Republic of China
| | - Xiaomeng Ren
- 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
| | - 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
| | - 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
| | - Xiangtao Mo
- 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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Florez AM, Suarez-Barrera MO, Morales GM, Rivera KV, Orduz S, Ochoa R, Guerra D, Muskus C. Toxic Activity, Molecular Modeling and Docking Simulations of Bacillus thuringiensis Cry11 Toxin Variants Obtained via DNA Shuffling. Front Microbiol 2018; 9:2461. [PMID: 30386315 PMCID: PMC6199390 DOI: 10.3389/fmicb.2018.02461] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Accepted: 09/25/2018] [Indexed: 11/23/2022] Open
Abstract
The Cry11 family belongs to a large group of δ-endotoxins that share three distinct structural domains. Among the dipteran-active toxins referred to as three-domain Cry11 toxins, the Cry11Aa protein from Bacillus thuringiensis subsp. israelensis (Bti) has been the most extensively studied. Despite the potential of Bti as an effective biological control agent, the understanding of Cry11 toxins remains incomplete. In this study, five Cry11 variants obtained via DNA shuffling displayed toxic activity against Aedes aegypti and Culex quinquefasciatus. Three of these Cry11 variants (8, 23, and 79) were characterized via 3D modeling and analysis of docking with ALP1. The relevant mutations in these variants, such as deletions, insertions and point mutations, are discussed in relation to their structural domains, toxic activities and toxin-receptor interactions. Importantly, deletion of the N-terminal segment in domain I was not associated with any change in toxic activity, and domain III exhibited higher sequence variability than domains I and II. Variant 8 exhibited up to 3.78- and 6.09-fold higher toxicity to A. aegypti than Cry11Bb and Cry11Aa, respectively. Importantly, variant 79 showed an α-helix conformation at the C-terminus and formed crystals retaining toxic activity. These findings indicate that five Cry11 variants were preferentially reassembled from the cry11Aa gene during DNA shuffling. The mutations described in loop 2 and loop 3 of domain II provide valuable information regarding the activity of Cry11 toxins against A. aegypti and C. quinquefasciatus larvae and reveal new insights into the application of directed evolution strategies to study the genetic variability of specific domains in cry11 family genes.
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Affiliation(s)
- Alvaro Mauricio Florez
- RG Microbial Ecology: Metabolism, Genomics & Evolution, Microbiomas Foundation, Chía, Colombia
| | - Miguel Orlando Suarez-Barrera
- Laboratorio de Biología Molecular y Biotecnología, Universidad de Santander, Bucaramanga, Colombia.,Escuela de Medicina, Facultad de Salud, Universidad Industrial de Santander, Bucaramanga, Colombia
| | - Gloria M Morales
- Laboratorio de Biología Molecular y Biotecnología, Universidad de Santander, Bucaramanga, Colombia
| | - Karen Viviana Rivera
- Laboratorio de Biología Molecular y Biotecnología, Universidad de Santander, Bucaramanga, Colombia
| | - Sergio Orduz
- Grupo Biologa Funcional, Laboratorio de Prospección y Diseo de Biomoléculas, Escuela de Biociencias, Universidad Nacional, Sede Medellín, Colombia
| | - Rodrigo Ochoa
- Programa de Estudio y Control de Enfermedades Tropicales PECET, Unidad de Biologa Molecular y Computacional-UBMC, Universidad de Antioquía, Medellín, Colombia
| | - Diego Guerra
- Programa de Estudio y Control de Enfermedades Tropicales PECET, Unidad de Biologa Molecular y Computacional-UBMC, Universidad de Antioquía, Medellín, Colombia
| | - Carlos Muskus
- Programa de Estudio y Control de Enfermedades Tropicales PECET, Unidad de Biologa Molecular y Computacional-UBMC, Universidad de Antioquía, Medellín, Colombia
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