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Tavares CS, Wang X, Ghosh S, Mishra R, Bonning BC. Bacillus thuringiensis-derived pesticidal proteins toxic to the whitefly, Bemisia tabaci. J Invertebr Pathol 2025; 210:108291. [PMID: 39986348 DOI: 10.1016/j.jip.2025.108291] [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: 11/18/2024] [Revised: 02/10/2025] [Accepted: 02/17/2025] [Indexed: 02/24/2025]
Abstract
The whitefly, Bemisia tabaci, is among the most important threats to global agriculture and food security. In addition to losses associated with feeding, B. tabaci vectors hundreds of plant viruses, many of which cause severe disease in staple food crops. The management of B. tabaci is confounded by extensive resistance to chemical insecticides. While pesticidal proteins derived from entomopathogenic bacteria such as Bacillus thuringiensis (Bt) could provide for alternative management approaches, only one pesticidal protein with toxicity to B. tabaci has been identified. Here we screened 11 Bt-derived pesticidal proteins from several different structural classes against the highly invasive, Middle East-Asian Minor 1 (MEAM1) cryptic species of B. tabaci, and assessed the impact of a B. tabaci-active protein on the gut epithelial membrane by transmission electron microscopy. The pesticidal proteins were expressed in Bt or in Escherichia coli and purified for use in bioassays. The toxicity of purified proteins was first assessed by feeding adults on a single dose followed by lethal concentration (LC50) determination for proteins with significant mortality relative to the buffer control. The proteins Tpp78Aa1, Tpp78Ba1, and Cry1Ca were toxic to B. tabaci with LC50 values of 99, 96, and 351 µg/mL, respectively. Disruption of the brush border and severe reduction in microvilli on the gut surface caused by Tpp78Aa1 is consistent with the mode of action of Bt-derived pesticidal proteins. These proteins may provide valuable tools for the integrated management of B. tabaci populations and associated reduced incidence of B. tabaci vectored plant viral diseases.
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Affiliation(s)
- Clebson S Tavares
- Department of Entomology and Nematology, University of Florida, PO Box 110620, Gainesville, FL 32611, USA
| | - Xinyue Wang
- Department of Entomology and Nematology, University of Florida, PO Box 110620, Gainesville, FL 32611, USA
| | - Saptarshi Ghosh
- Department of Entomology and Nematology, University of Florida, PO Box 110620, Gainesville, FL 32611, USA
| | - Ruchir Mishra
- Department of Entomology and Nematology, University of Florida, PO Box 110620, Gainesville, FL 32611, USA
| | - Bryony C Bonning
- Department of Entomology and Nematology, University of Florida, PO Box 110620, Gainesville, FL 32611, USA.
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Tavares CS, Stelinski LL, Bonning BC. The sandwich feeding assay for use with first instar nymphs of the Asian citrus psyllid, Diaphorina citri confirms the high susceptibility of this life stage to bacterial pesticidal proteins. J Invertebr Pathol 2024; 207:108208. [PMID: 39317311 DOI: 10.1016/j.jip.2024.108208] [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: 06/21/2024] [Revised: 08/09/2024] [Accepted: 09/20/2024] [Indexed: 09/26/2024]
Abstract
Citrus greening or huanglongbing is the most important disease of citrus and threatens citrus production worldwide. As nymphs of Diaphorina citri play a crucial role in the acquisition and transmission of the citrus greening bacterium, suppression of this life stage is particularly important. However, the lack of a tractable feeding assay for use with first instar D. citri nymphs has impeded assessment of the toxicity of bioactives. Of several bacterial pesticidal proteins (BPP) that are toxic to D. citri adults, Mpp51Aa1 and Cry1Ba1, which have LC50 values of 110 and 120 µg/mL respectively in adults, were fed to 1st instar nymphs in a newly developed assay. For this new sandwich feeding assay, parafilm layers containing feeding solution were placed on top of two 35 mm Petri dishes, with a concave surface created on each. Fifty nymphs were transferred to the membrane on one Petri dish, and the second Petri dish placed on the top to create a "sandwich" with the 1st instar nymphs in the middle. Nymphs were fed for four days and the LC50 values for Mpp51Aa1 and Cry1Ba1 were calculated at 6.7 and 41.6 µg/mL respectively. Bioassays with bioengineered plants expressing Cry1Ba1 confirmed that the majority of D. citri mortality occurs during the 1st instar nymph stage, while egg laying adults are much less susceptible. Taken together, these results confirm that 1st instar D. citri nymphs are more susceptible to BPP than adults and demonstrate the utility of the sandwich feeding assay for effective screening of BPPs prior to investment into production of transgenic plants.
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Affiliation(s)
- Clebson S Tavares
- Entomology and Nematology Department, University of Florida, Gainesville, FL, USA.
| | - Lukasz L Stelinski
- Citrus Research and Education Center, University of Florida, IFAS, Lake Alfred, FL, USA
| | - Bryony C Bonning
- Entomology and Nematology Department, University of Florida, Gainesville, FL, USA
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Tavares CS, Mishra R, Kishk A, Wang X, Ghobrial PN, Killiny N, Bonning BC. The beta pore-forming bacterial pesticidal protein Tpp78Aa1 is toxic to the Asian citrus psyllid vector of the citrus greening bacterium. J Invertebr Pathol 2024; 204:108122. [PMID: 38710321 DOI: 10.1016/j.jip.2024.108122] [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: 04/02/2024] [Revised: 04/22/2024] [Accepted: 05/02/2024] [Indexed: 05/08/2024]
Abstract
The Asian citrus psyllid (ACP) Diaphorina citri transmits the causative agent of huanglongbing, or citrus greening disease, that has decimated global citrus production. Pesticidal proteins derived from bacteria such as Bacillus thuringiensis (Bt) can provide effective and environmentally friendly alternatives for management of D. citri, but few with sufficient toxicity to D. citri have been identified. Here, we report on the toxicity of 14 Bt-derived pesticidal proteins from five different structural groups against D. citri. These proteins were selected based on previously reported toxicity to other hemipteran species and on pesticidal protein availability. Most of the proteins were expressed in Escherichia coli and purified from inclusion bodies or His-tag affinity purification, while App6Aa2 was expressed in Bt and purified from spore/crystal mixtures. Pesticidal proteins were initially screened by feeding psyllids on a single dose, and lethal concentration (LC50) then determined for proteins with significantly greater mortality than the buffer control. The impact of CLas infection of D. citri on toxicity was assessed for selected proteins via topical feeding. The Bt protein Tpp78Aa1 was toxic to D. citri adults with an LC50 of approximately 204 µg/mL. Nymphs were more susceptible to Tpp78Aa1 than adults but no significant difference in susceptibility was observed between healthy and CLas-infected nymphs or adults. Tpp78Aa1 and other reported D. citri-active proteins may provide valuable tools for suppression of D. citri populations.
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Affiliation(s)
- Clebson S Tavares
- Department of Entomology and Nematology, University of Florida, Gainesville, FL, USA.
| | - Ruchir Mishra
- Department of Entomology and Nematology, University of Florida, Gainesville, FL, USA
| | - Abdelaziz Kishk
- Department of Plant Pathology, Citrus Research and Education Center, IFAS, University of Florida, Lake Alfred, FL 33850, USA; Department of Plant Protection, Faculty of Agriculture, Tanta University 31527, Egypt
| | - Xinyue Wang
- Department of Entomology and Nematology, University of Florida, Gainesville, FL, USA
| | - Pierre N Ghobrial
- Department of Entomology and Nematology, University of Florida, Gainesville, FL, USA
| | - Nabil Killiny
- Department of Plant Protection, Faculty of Agriculture, Tanta University 31527, Egypt
| | - Bryony C Bonning
- Department of Entomology and Nematology, University of Florida, Gainesville, FL, USA
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Kishk A, Dos Santos Tavares C, Mishra R, Bonning BC, Killiny N. Influence of 'Candidatus Liberibacter asiaticus' infection on the susceptibility of Asian citrus psyllid, Diaphorina citri to Bacillus thuringiensis pesticidal proteins, Mpp51Aa1 and Cry1Ba1. J Invertebr Pathol 2023; 200:107972. [PMID: 37460056 DOI: 10.1016/j.jip.2023.107972] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Revised: 06/29/2023] [Accepted: 07/14/2023] [Indexed: 07/25/2023]
Abstract
The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae) transmits the Gram-negative bacterium 'Candidatus Liberibacter asiaticus' that causes citrus greening disease. While chemical control has been the main management strategy for limiting D. citri, the widespread usage of chemical sprays has decreased the susceptibility of D. citri to most insecticides. Pesticidal proteins produced by the bacterium Bacillus thuringiensis (Bt) are active against a wide variety of insects and provide a more sustainable approach to insect control. Herein, we investigated the impact of 'Ca. L. asiaticus' infection of D. citri on the toxicity of two Bt proteins (Mpp51Aa1 and Cry1Ba1). Proteins were delivered to healthy and 'Ca. L. asiaticus'-infected D. citri via topical feeding application. The LC50 values of Mpp51Aa1 and Cry1Ba1 were calculated for both nymphs and adults. Additionally, we evaluated the effect of each protein on the survival probability and life span of healthy and 'Ca. L. asiaticus'-infected D. citri. The LC50 values indicated that adults and nymphs were more susceptible to Mpp51Aa1 than to Cry1Ba1 in both healthy and 'Ca. L. asiaticus'-infected D. citri. 'Ca. L. asiaticus'-infected adults and nymphs were more susceptible to Mpp51Aa1 and Cry1Ba1 than healthy insects, and nymphs were more susceptible to Mpp51Aa1 and Cry1Ba1 than adults. Moreover, we found that Mpp51Aa1 had a greater impact than Cry1Ba1 on the survival and lifespan of adults, and 'Ca. L. asiaticus'-infected insects were more affected by these pesticidal proteins than healthy adults. These results have important implications for the use of pesticidal proteins in D. citri management in Florida and elsewhere given the widespread presence of 'Ca. L. asiaticus' in the D. citri population. In this era of eco-friendly control strategies, Bt-derived pesticidal proteins provide a promising avenue to reducing the application of chemical insecticides for D. citri management.
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Affiliation(s)
- Abdelaziz Kishk
- Department of Plant Pathology, Citrus Research and Education Center, IFAS, University of Florida, Lake Alfred, FL, 33850, USA; Department of Plant Protection, Faculty of Agriculture, Tanta University, 31527, Egypt
| | | | - Ruchir Mishra
- Department of Entomology and Nematology, IFAS, University of Florida, Gainesville, FL 32611, USA
| | - Bryony C Bonning
- Department of Entomology and Nematology, IFAS, University of Florida, Gainesville, FL 32611, USA
| | - Nabil Killiny
- Department of Plant Pathology, Citrus Research and Education Center, IFAS, University of Florida, Lake Alfred, FL, 33850, USA.
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Mishra R, Narayana R, Ibanez F, Achor D, Shilts T, El-Mohtar C, Orbović V, Stelinski LL, Bonning BC. Bacterial Pesticidal Protein Mpp51Aa1 Delivered via Transgenic Citrus Severely Impacts the Fecundity of Asian Citrus Psyllid, Diaphorina citri. Appl Environ Microbiol 2023; 89:e0072323. [PMID: 37458593 PMCID: PMC10467345 DOI: 10.1128/aem.00723-23] [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: 05/03/2023] [Accepted: 06/26/2023] [Indexed: 08/31/2023] Open
Abstract
The Asian citrus psyllid (ACP) Diaphorina citri vectors the causative agent of citrus greening disease that has the capacity to decimate citrus production. As an alternative and more sustainable approach to manage D. citri than repeated application of chemical insecticides, we investigated the potential use of the bacteria-derived pesticidal protein, Mpp51Aa1, when delivered by transgenic Citrus sinensis cv. Valencia sweet orange or Citrus paradisi cv. Duncan grapefruit. Following confirmation of transcription and translation of mpp51aa1 by transgenic plants, no impact of Mpp51Aa1 expression was seen on D. citri host plant choice between transgenic and control Duncan grapefruit plants. A slight but significant drop in survival of adult psyllids fed on these transgenic plants was noted relative to those fed on control plants. In line with this result, damage to the gut epithelium consistent with that caused by pore-forming proteins was only observed in a minority of adult D. citri fed on the transgenic Duncan grapefruit. However, greater impacts were observed on nymphs than on adults, with a 40% drop in the survival of nymphs fed on transgenic Duncan grapefruit relative to those fed on control plants. For Valencia sweet orange, a 70% decrease in the number of eggs laid by adult D. citri on transgenic plants was noted relative to those on control plants, with a 90% drop in emergence of progeny. These impacts that contrast with those associated with other bacterial pesticidal proteins and the potential for use of Mpp51Aa1-expressing transgenic plants for suppression of D. citri populations are discussed. IMPORTANCE Pesticidal proteins derived from bacteria such as Bacillus thuringiensis are valuable tools for management of agricultural insect pests and provide a sustainable alternative to the application of chemical insecticides. However, relatively few bacterial pesticidal proteins have been used for suppression of hemipteran or sap-sucking insects such as the Asian citrus psyllid, Diaphorina citri. This insect is particularly important as the vector of the causative agent of citrus greening, or huanglongbing disease, which severely impacts global citrus production. In this study, we investigated the potential of transgenic citrus plants that produce the pesticidal protein Mpp51Aa1. While adult psyllid mortality on transgenic plants was modest, the reduced number of eggs laid by exposed adults and the decreased survival of progeny was such that psyllid populations dropped by more than 90%. These results provide valuable insight for potential deployment of Mpp51Aa1 in combination with other control agents for the management of D. citri.
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Affiliation(s)
- Ruchir Mishra
- Entomology and Nematology Department, University of Florida, Gainesville, Florida, USA
| | - Ravishankar Narayana
- Citrus Research and Education Center, University of Florida, IFAS, Lake Alfred, Florida, USA
| | - Freddy Ibanez
- Citrus Research and Education Center, University of Florida, IFAS, Lake Alfred, Florida, USA
| | - Diann Achor
- Citrus Research and Education Center, University of Florida, IFAS, Lake Alfred, Florida, USA
| | - Turksen Shilts
- Citrus Research and Education Center, University of Florida, IFAS, Lake Alfred, Florida, USA
| | - Choaa El-Mohtar
- Citrus Research and Education Center, University of Florida, IFAS, Lake Alfred, Florida, USA
| | - Vladimir Orbović
- Citrus Research and Education Center, University of Florida, IFAS, Lake Alfred, Florida, USA
| | - Lukasz L. Stelinski
- Citrus Research and Education Center, University of Florida, IFAS, Lake Alfred, Florida, USA
| | - Bryony C. Bonning
- Entomology and Nematology Department, University of Florida, Gainesville, Florida, USA
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