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Pacheco S, Gallegos AS, Peláez-Aguilar ÁE, Sánchez J, Gómez I, Soberón M, Bravo A. CRISPR-Cas9 knockout of membrane-bound alkaline phosphatase or cadherin does not confer resistance to Cry toxins in Aedes aegypti. PLoS Negl Trop Dis 2024; 18:e0012256. [PMID: 38870209 PMCID: PMC11207138 DOI: 10.1371/journal.pntd.0012256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2024] [Revised: 06/26/2024] [Accepted: 05/30/2024] [Indexed: 06/15/2024] Open
Abstract
The Aedes aegypti cadherin-like protein (Aae-Cad) and the membrane-bound alkaline phosphatase (Aae-mALP) are membrane proteins identified as putative receptors for the larvicidal Cry toxins produced by Bacillus thuringiensis subsp. israelensis bacteria. Cry toxins are the most used toxins in the control of different agricultural pest and mosquitos. Despite the relevance of Aae-Cad and Aae-mALP as possible toxin-receptors in mosquitoes, previous efforts to establish a clear functional connection among them and Cry toxins activity have been relatively limited. In this study, we used CRISPR-Cas9 to generate knockout (KO) mutations of Aae-Cad and Aae-mALP. The Aae-mALP KO was successfully generated, in contrast to the Aae-Cad KO which was obtained only in females. The female-linked genotype was due to the proximity of aae-cad gene to the sex-determining loci (M:m). Both A. aegypti KO mutant populations were viable and their insect-development was not affected, although a tendency on lower egg hatching rate was observed. Bioassays were performed to assess the effects of these KO mutations on the susceptibility of A. aegypti to Cry toxins, showing that the Aae-Cad female KO or Aae-mALP KO mutations did not significantly alter the susceptibility of A. aegypti larvae to the mosquitocidal Cry toxins, including Cry11Aa, Cry11Ba, Cry4Ba, and Cry4Aa. These findings suggest that besides the potential participation of Aae-Cad and Aae-mALP as Cry toxin receptors in A. aegypti, additional midgut membrane proteins are involved in the mode of action of these insecticidal toxins.
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Affiliation(s)
- Sabino Pacheco
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), Cuernavaca, Morelos, Mexico
| | - Adrián S. Gallegos
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), Cuernavaca, Morelos, Mexico
| | - Ángel E. Peláez-Aguilar
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), Cuernavaca, Morelos, Mexico
| | - Jorge Sánchez
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), Cuernavaca, Morelos, Mexico
| | - Isabel Gómez
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), Cuernavaca, Morelos, Mexico
| | - Mario Soberón
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), Cuernavaca, Morelos, Mexico
| | - Alejandra Bravo
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), 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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Alam I, Batool K, Idris AL, Tan W, Guan X, Zhang L. Role of Lectin in the Response of Aedes aegypti Against Bt Toxin. Front Immunol 2022; 13:898198. [PMID: 35634312 PMCID: PMC9136036 DOI: 10.3389/fimmu.2022.898198] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Accepted: 04/19/2022] [Indexed: 12/05/2022] Open
Abstract
Aedes aegypti is one of the world’s most dangerous mosquitoes, and a vector of diseases such as dengue fever, chikungunya virus, yellow fever, and Zika virus disease. Currently, a major global challenge is the scarcity of antiviral medicine and vaccine for arboviruses. Bacillus thuringiensis var israelensis (Bti) toxins are used as biological mosquito control agents. Endotoxins, including Cry4Aa, Cry4Ba, Cry10Aa, Cry11Aa, and Cyt1Aa, are toxic to mosquitoes. Insect eradication by Cry toxin relies primarily on the interaction of cry toxins with key toxin receptors, such as aminopeptidase (APN), alkaline phosphatase (ALP), cadherin (CAD), and ATP-binding cassette transporters. The carbohydrate recognition domains (CRDs) of lectins and domains II and III of Cry toxins share similar structural folds, suggesting that midgut proteins, such as C-type lectins (CTLs), may interfere with interactions among Cry toxins and receptors by binding to both and alter Cry toxicity. In the present review, we summarize the functional role of C-type lectins in Ae. aegypti mosquitoes and the mechanism underlying the alteration of Cry toxin activity by CTLs. Furthermore, we outline future research directions on elucidating the Bti resistance mechanism. This study provides a basis for understanding Bti resistance, which can be used to develop novel insecticides.
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Affiliation(s)
- Intikhab Alam
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
- Key Lab of Biopesticides and Chemical Biology, MOE, Fujian Agriculture and Forestry University, Fuzhou, China
- College of Life Sciences, South China Agricultural University, Guangzhou, China
| | - Khadija Batool
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
- Key Lab of Biopesticides and Chemical Biology, MOE, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Aisha Lawan Idris
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
- Key Lab of Biopesticides and Chemical Biology, MOE, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Weilong Tan
- Nanjing Bioengineering (Gene) Technology Center for Medicines, Nanjing, China
| | - Xiong Guan
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
- Key Lab of Biopesticides and Chemical Biology, MOE, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Lingling Zhang
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
- Key Lab of Biopesticides and Chemical Biology, MOE, Fujian Agriculture and Forestry University, Fuzhou, China
- *Correspondence: Lingling Zhang,
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Zhu Q, Gao M, Lu L, Liu X. Synergism of Bacillus thuringiensis Toxin Cry1Ac by a Fragment of Toxin-Binding Polycalin from Plutella xylostella. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2021; 69:11816-11824. [PMID: 34596393 DOI: 10.1021/acs.jafc.1c03156] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The continued success of pest control using insecticidal crystal (Cry) proteins from Bacillus thuringiensis (Bt) in transgenic plants was threatened by the evolution of resistance. Previous studies suggested that polycalin from Plutella xylostella could bind to Cry1Ac toxin as a potential receptor. In this study, a fragment of P. xylostella polycalin (Pxpolycalinf, G2209-A2942) containing a carboxyl-terminal GPI-anchored signal peptide was cloned and expressed. Purified Pxpolycalinf retained the binding ability to Cry1Ac and synergized Cry1Ac toxicity to the third larvae of P. xylostella in bioassays. Moreover, the polyclonal antibody of Pxpolycalinf decreased the Cry1Ac activity after being fed together with normal food. Further, the ELISA results showed the concentration-dependent binding of Pxpolycalinf to P. xylostella brush border membrane vesicles (BBMV). Spodoptera frugiperda 9 (Sf9) cells expressing Pxpolycalinf were not susceptive to Cry1Ac, whereas Pxpolycalinf increased Cry1Ac cytotoxicity to Sf9 cells expressing P. xylostella ATP-dependent binding cassette transporter C2 (PxABCC2). Immunolocalization presented the binding of Pxpolycalinf to the Sf9 cell membrane, and ELISA showed the concentration-dependent binding of Pxpolycalinf to Sf9 cell extraction. These results here provide the first evidence that a fragment of P. xylostella polycalin, a potential receptor of Cry1Ac, synergizes Cry1Ac toxicity to P. xylostella larvae and Sf9 cells expressing PxABCC2.
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Affiliation(s)
- Qing Zhu
- Key Lab of Food Quality and Safety of Jiangsu Province-State Key Laboratory Breeding Base, Key Laboratory of Control Technology and Standard for Agro -product Safety and Quality, Ministry of Agriculture, Institute of Food Safety and Nutrition, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China
| | - Meijing Gao
- Key Lab of Food Quality and Safety of Jiangsu Province-State Key Laboratory Breeding Base, Key Laboratory of Control Technology and Standard for Agro -product Safety and Quality, Ministry of Agriculture, 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, Key Laboratory of Control Technology and Standard for Agro -product Safety and Quality, Ministry of Agriculture, Institute of Food Safety and Nutrition, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China
| | - Xianjin Liu
- Key Lab of Food Quality and Safety of Jiangsu Province-State Key Laboratory Breeding Base, Key Laboratory of Control Technology and Standard for Agro -product Safety and Quality, Ministry of Agriculture, Institute of Food Safety and Nutrition, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China
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Bacterial Toxins Active against Mosquitoes: Mode of Action and Resistance. Toxins (Basel) 2021; 13:toxins13080523. [PMID: 34437394 PMCID: PMC8402332 DOI: 10.3390/toxins13080523] [Citation(s) in RCA: 45] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 06/18/2021] [Accepted: 06/19/2021] [Indexed: 12/25/2022] Open
Abstract
Larvicides based on the bacteria Bacillus thuringiensis svar. israelensis (Bti) and Lysinibacillus sphaericus are effective and environmentally safe compounds for the control of dipteran insects of medical importance. They produce crystals that display specific and potent insecticidal activity against larvae. Bti crystals are composed of multiple protoxins: three from the three-domain Cry type family, which bind to different cell receptors in the midgut, and one cytolytic (Cyt1Aa) protoxin that can insert itself into the cell membrane and act as surrogate receptor of the Cry toxins. Together, those toxins display a complex mode of action that shows a low risk of resistance selection. L. sphaericus crystals contain one major binary toxin that display an outstanding persistence in field conditions, which is superior to Bti. However, the action of the Bin toxin based on its interaction with a single receptor is vulnerable for resistance selection in insects. In this review we present the most recent data on the mode of action and synergism of these toxins, resistance issues, and examples of their use worldwide. Data reported in recent years improved our understanding of the mechanism of action of these toxins, showed that their combined use can enhance their activity and counteract resistance, and reinforced their relevance for mosquito control programs in the future years.
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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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Munawar K, Alahmed AM, Khalil SMS. Delivery Methods for RNAi in Mosquito Larvae. JOURNAL OF INSECT SCIENCE (ONLINE) 2020; 20:5877674. [PMID: 32725159 PMCID: PMC7387866 DOI: 10.1093/jisesa/ieaa074] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2020] [Indexed: 05/23/2023]
Abstract
Mosquito-transmitted diseases pose a threat for a great portion of the world population. Chemical insecticides are the main tool for mosquito control. Heavy dependence on chemicals created several problems such as resistance development in many mosquito species, environmental effects, and human health issues. Other tools for mosquito control were developed and used in some parts of the world. Ribonucleic acid interference (RNAi) is a reverse genetic mechanism that was recently introduced as a new tool for pest control. Regarding mosquito, RNAi was used to study gene function and to discover genes that can be used as targets for control purposes. Several delivery methods are used to induce RNAi in mosquito larvae. Some methods such as injection and soaking are used routinely in RNAi research but have no application in the field. Other methods such as nanoparticles and microbes have some characteristics that make them good candidates for field application. In this report, we will focus on delivery methods for RNAi in mosquito larvae and will give examples for each method.
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Affiliation(s)
- Kashif Munawar
- Plant Protection Department, College of Food and Agricultural Sciences, King Saud University, Riyadh, Saudi Arabia
| | - Azzam M Alahmed
- Plant Protection Department, College of Food and Agricultural Sciences, King Saud University, Riyadh, Saudi Arabia
| | - Sayed M S Khalil
- Plant Protection Department, College of Food and Agricultural Sciences, King Saud University, Riyadh, Saudi Arabia
- Agricultural Genetic Engineering Research Institute, Agricultural Research Center, Giza, Egypt
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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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Chen J, Aimanova KG, Gill SS. Aedes cadherin receptor that mediates Bacillus thuringiensis Cry11A toxicity is essential for mosquito development. PLoS Negl Trop Dis 2020; 14:e0007948. [PMID: 32012156 PMCID: PMC7018227 DOI: 10.1371/journal.pntd.0007948] [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: 05/04/2019] [Revised: 02/13/2020] [Accepted: 11/25/2019] [Indexed: 11/20/2022] Open
Abstract
Aedes cadherin (AaeCad, AAEL024535) has been characterized as a receptor for Bacillus thuringiensis subsp. israelensis (Bti) Cry11A toxins. However, its role in development is still unknown. In this study, we modified the cadherin gene using ZFN and TALEN. Even though we obtained heterozygous deletions, no homozygous mutants were viable. Because ZFN and TALEN have lower off-targets than CRISPR/Cas9, we conclude the cadherin gene is essential for Aedes development. In contrast, in lepidopteran insects loss of a homologous cadherin does not appear to be lethal, since homozygous mutants are viable. To analyze the role of AaeCad in vivo, we tagged this protein with EGFP using CRISPR-Cas9-mediated homologous recombination and obtained a homozygous AaeCad-EGFP line. Addition of Aedes Rad51 mRNA enhanced the rate of recombination. We then examined AaeCad protein expression in most tissues and protein dynamics during mosquito development. We observe that AaeCad is expressed in larval and adult midgut-specific manner and its expression pattern changed during the mosquito development. Confocal images showed AaeCad has high expression in larval caecae and posterior midgut, and also in adult midgut. Expression of AaeCad is observed primarily in the apical membranes of epithelial cells, and not in cell-cell junctions. The expression pattern observed suggests AaeCad does not appear to play a role in these junctions. However, we cannot exclude its role beyond cell-cell adhesion in the midgut. We also observed that Cry11A bound to the apical side of larval gastric caecae and posterior midgut cells exactly where AaeCad-EGFP was expressed. Their co-localization suggests that AaeCad is indeed a receptor for the Cry11A toxin. Using this mosquito line we also observed that low doses of Cry11A toxin caused the cells to slough off membranes, which likely represents a defense mechanism, to limit cell damage from Cry11A toxin pores formed in the cell membrane. A number of receptors for Bt Cry toxins, have been identified and characterized, including cadherin proteins. However, the role of these proteins in the insect is unknown and there have been few efforts to elucidate their function. First, in this study we show that in the mosquito, Aedes aegypti, the cadherin protein is essential for development. Secondly, we provide evidence that AaeCad plays a role in the apical membrane and the maintenance of midgut integrity by gene tagging using CRISPR/Cas9, which overcomes the limitation of receptor localization using antibodies in previous studies. These investigations are helpful to further investigate the physiological function of AaeCad. Moreover, this study demonstrated successful tagging of an essential gene with fluorescence protein in a non-model insect. In addition, this study showed that epithelium thinning is possibly a conserved mechanism for host defense against pore-forming toxins, like Cry11A.
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Affiliation(s)
- Jianwu Chen
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, California, United States of America
| | - Karly G. Aimanova
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, California, United States of America
| | - Sarjeet S. Gill
- Department of Molecular, Cell and Systems Biology, University of California, Riverside, California, United States of America
- * E-mail:
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Negri A, Ferrari M, Nodari R, Coppa E, Mastrantonio V, Zanzani S, Porretta D, Bandi C, Urbanelli S, Epis S. Gene silencing through RNAi and antisense Vivo-Morpholino increases the efficacy of pyrethroids on larvae of Anopheles stephensi. Malar J 2019; 18:294. [PMID: 31462239 PMCID: PMC6712854 DOI: 10.1186/s12936-019-2925-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Accepted: 08/17/2019] [Indexed: 11/25/2022] Open
Abstract
Background Insecticides are still at the core of insect pest and vector control programmes. Several lines of evidence indicate that ABC transporters are involved in detoxification processes against insecticides, including permethrin and other pyrethroids. In particular, the ABCG4 gene, a member of the G subfamily, has consistently been shown to be up-regulated in response to insecticide treatments in the mosquito malaria vector Anopheles stephensi (both adults and larvae). Methods To verify the actual involvement of this transmembrane protein in the detoxification process of permethrin, bioassays on larvae of An. stephensi, combining the insecticide with a siRNA, specifically designed for the inhibition of ABCG4 gene expression were performed. Administration to larvae of the same siRNA, labeled with a fluorescent molecule, was effected to investigate the systemic distribution of the inhibitory RNA into the larval bodies. Based on siRNA results, similar experiments using antisense Vivo-Morpholinos (Vivo-MOs) were effected. These molecules, compared to siRNA, are expected to guarantee a higher stability in environmental conditions and in the insect gut, and present thus a higher potential for future in-field applications. Results Bioassays using two different concentrations of siRNA, associated with permethrin, led to an increase of larval mortality, compared with results with permethrin alone. These outcomes confirm that ABCG4 transporter plays a role in the detoxification process against the selected insecticide. Moreover, after fluorescent labelling, it was shown the systemic dissemination of siRNA in different body districts of An. stephensi larvae, which suggest a potential systemic effect of the molecule. At the same time, results of Vivo-MO experiments were congruent with those obtained using siRNA, thus confirming the potential of ABCG4 inhibition as a strategy to increase permethrin susceptibility in mosquitoes. For the first time, Vivo-MOs were administered in water to larvae, with evidence for a biological effect. Conclusions Targeting ABCG4 gene for silencing through both techniques resulted in an increased pyrethroid efficacy. These results open the way toward the possibility to exploit ABCG4 inhibition in the context of integrated programmes for the control An. stephensi mosquitoes and malaria transmission.
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Affiliation(s)
- Agata Negri
- Department of Environmental Biology, Sapienza University of Rome, Via dei Sardi 70, 00185, Rome, Italy.,Department of Biosciences and Pediatric Clinical Research Center "Romeo ed Enrica Invernizzi", University of Milan, Via Celoria 26, 20133, Milan, Italy.,Centro Interuniversitario di Ricerca sulla Malaria/Italian Malaria Network, Via del Giochetto, 06126, Perugia, Italy
| | - Marco Ferrari
- Department of Biosciences and Pediatric Clinical Research Center "Romeo ed Enrica Invernizzi", University of Milan, Via Celoria 26, 20133, Milan, Italy.,Texas Biomedical Research Institute, San Antonio, 7620 NW Loop 410, San Antonio, TX, 78227-5301, USA
| | - Riccardo Nodari
- Department of Biosciences and Pediatric Clinical Research Center "Romeo ed Enrica Invernizzi", University of Milan, Via Celoria 26, 20133, Milan, Italy.,Centro Interuniversitario di Ricerca sulla Malaria/Italian Malaria Network, Via del Giochetto, 06126, Perugia, Italy
| | - Edoardo Coppa
- Department of Biosciences and Pediatric Clinical Research Center "Romeo ed Enrica Invernizzi", University of Milan, Via Celoria 26, 20133, Milan, Italy
| | - Valentina Mastrantonio
- Department of Environmental Biology, Sapienza University of Rome, Via dei Sardi 70, 00185, Rome, Italy
| | - Sergio Zanzani
- Department of Veterinary Medicine-DIMEVET, Università degli Studi di Milano, Via Celoria, 10, 20133, Milan, Italy
| | - Daniele Porretta
- Department of Environmental Biology, Sapienza University of Rome, Via dei Sardi 70, 00185, Rome, Italy
| | - Claudio Bandi
- Department of Biosciences and Pediatric Clinical Research Center "Romeo ed Enrica Invernizzi", University of Milan, Via Celoria 26, 20133, Milan, Italy.,Centro Interuniversitario di Ricerca sulla Malaria/Italian Malaria Network, Via del Giochetto, 06126, Perugia, Italy
| | - Sandra Urbanelli
- Department of Environmental Biology, Sapienza University of Rome, Via dei Sardi 70, 00185, Rome, Italy
| | - Sara Epis
- Department of Biosciences and Pediatric Clinical Research Center "Romeo ed Enrica Invernizzi", University of Milan, Via Celoria 26, 20133, Milan, Italy. .,Centro Interuniversitario di Ricerca sulla Malaria/Italian Malaria Network, Via del Giochetto, 06126, Perugia, Italy.
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11
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Du L, Chen G, Han L, Peng Y. Cadherin CsCad plays differential functional roles in Cry1Ab and Cry1C intoxication in Chilo suppressalis. Sci Rep 2019; 9:8507. [PMID: 31186483 PMCID: PMC6559963 DOI: 10.1038/s41598-019-44451-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Accepted: 04/25/2019] [Indexed: 12/11/2022] Open
Abstract
Transgenic rice lines expressing Bacillus thuringiensis (Bt) toxins have been successfully developed for the control of Chilo suppressalis. However, the evolution of insect resistance is a major threat to Bt rice durability. Bt toxins function by binding specific receptors in the midgut of target insects; specifically, cadherin proteins have been identified as Cry toxin receptors in diverse lepidopteran species. Here, we report the functional roles of cadherin CsCad in the midgut of C. suppressalis in Cry1Ab and Cry1C toxicity. We expressed a recombinant truncated CsCad peptide (CsCad-CR11-MPED) in Escherichia coli that included the eleventh cadherin repeat and MPED region. Based on ligand blotting and ELISA binding assays, the CsCad-CR11-MPED peptide specifically bound Cry1Ab with high affinity but weakly bound Cry1C. The CsCad-CR11-MPED peptide significantly enhanced the susceptibility of C. suppressalis larvae to Cry1Ab but not Cry1C. Furthermore, the knockdown of endogenous CsCad with Stealth siRNA reduced C. suppressalis larval susceptibility to Cry1Ab but not Cry1C, suggesting that CsCad plays differential functional roles in Cry1Ab and Cry1C intoxication in C. suppressalis. This information directly enhances our understanding of the potential resistance mechanisms of C. suppressalis against Bt toxins and may assist in the development of effective strategies for delaying insect resistance.
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Affiliation(s)
- Lixiao Du
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, 100193, Beijing, China
| | - Geng Chen
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, 100193, Beijing, China
| | - Lanzhi Han
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, 100193, Beijing, China.
| | - Yufa Peng
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, 100193, Beijing, China
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12
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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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13
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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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14
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Silva-Brandão KL, Peruchi A, Seraphim N, Murad NF, Carvalho RA, Farias JR, Omoto C, Cônsoli FL, Figueira A, Brandão MM. Loci under selection and markers associated with host plant and host-related strains shape the genetic structure of Brazilian populations of Spodoptera frugiperda (Lepidoptera, Noctuidae). PLoS One 2018; 13:e0197378. [PMID: 29787608 PMCID: PMC5963752 DOI: 10.1371/journal.pone.0197378] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Accepted: 05/01/2018] [Indexed: 11/18/2022] Open
Abstract
We applied the ddRAD genotyping-by-sequencing technique to investigate the genetic distinctiveness of Brazilian populations of the noctuid moth Spodoptera frugiperda, the fall armyworm (FAW), and the role of host-plant association as a source of genetic diversification. By strain-genotyping all field-collected individuals we found that populations collected from corn were composed primarily of corn-strain individuals, while the population collected from rice was composed almost entirely of rice-strain individuals. Outlier analyses indicated 1,184 loci putatively under selection (ca. 15% of the total) related to 194 different Gene Ontologies (GOs); the most numerous GOs were nucleotide binding, ATP binding, metal-ion binding and nucleic-acid binding. The association analyses indicated 326 loci associated with the host plant, and 216 loci associated with the individual strain, including functions related to Bacillus thuringiensis and insecticide resistance. The genetic-structure analyses indicated a moderate level of differentiation among all populations, and lower genetic structure among populations collected exclusively from corn, which suggests that the population collected from rice has a strong influence on the overall genetic structure. Populations of S. frugiperda are structured partially due to the host plant, and pairs of populations using the same host plant are more genetically similar than pairs using different hosts. Loci putatively under selection are the main factors responsible for the genetic structure of these populations, which indicates that adaptive selection on important traits, including the response to control tactics, is acting in the genetic differentiation of FAW populations in Brazil.
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Affiliation(s)
- Karina Lucas Silva-Brandão
- Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, Campus "Luiz de Queiroz", Laboratório de Melhoramento de Plantas, Piracicaba, São Paulo, Brazil
- * E-mail:
| | - Aline Peruchi
- Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, Campus "Luiz de Queiroz", Laboratório de Melhoramento de Plantas, Piracicaba, São Paulo, Brazil
| | - Noemy Seraphim
- Instituto Federal de Educação, Ciência e Tecnologia de São Paulo, campus Campinas CTI Renato Archer, Campinas, São Paulo, Brazil
| | - Natália Faraj Murad
- Programa de Pós-graduação em Genética e Biologia Molecular, Centro de Biologia Molecular e Engenharia Genética, Universidade Estadual de Campinas, Campinas, São Paulo, Brazil
| | | | - Juliano Ricardo Farias
- Instituto Phytus, Departamento de Entomologia, Rua Duque de Caxias, Santa Maria, Rio Grande do Sul, Brazil
| | - Celso Omoto
- Escola Superior de Agricultura "Luiz de Queiroz", Universidade de São Paulo, Departamento de Entomologia e Acarologia, Piracicaba, São Paulo, Brazil
| | - Fernando Luis Cônsoli
- Escola Superior de Agricultura "Luiz de Queiroz", Universidade de São Paulo, Departamento de Entomologia e Acarologia, Piracicaba, São Paulo, Brazil
| | - Antonio Figueira
- Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, Campus "Luiz de Queiroz", Laboratório de Melhoramento de Plantas, Piracicaba, São Paulo, Brazil
| | - Marcelo Mendes Brandão
- Centro de Biologia Molecular e Engenharia Genética, Universidade Estadual de Campinas, Campinas, São Paulo, Brazil
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15
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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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16
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Chen J, Aimanova K, Gill SS. Functional characterization of Aedes aegypti alkaline phosphatase ALP1 involved in the toxicity of Cry toxins from Bacillus thuringiensis subsp. israelensis and jegathesan. Peptides 2017; 98:78-85. [PMID: 28587836 PMCID: PMC5705450 DOI: 10.1016/j.peptides.2017.05.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Revised: 05/24/2017] [Accepted: 05/30/2017] [Indexed: 10/19/2022]
Abstract
Presently three major groups of proteins from Aedes aegypti, cadherin, alkaline phosphatases (ALP) and aminopeptidases N (APN), have been identified as Cry11Aa toxin receptors. To further characterize their role on toxicity, transgenic mosquitoes with silenced Aedes cadherin expression were previously generated and the role of cadherin in mediating the toxicity of four different mosquitocidal toxins (Cry11Aa, Cry11Ba, Cry4Aa and Cry4Ba) was demonstrated. Here, we investigated the role of another reported Cry11Aa receptor, ALP1. As with Aedes cadherin, this protein is localized in the apical cell membrane of distal and proximal gastric caecae and the posterior midgut. We also successfully generated transgenic mosquitoes that knockdowned ALP1 transcript levels using an inducible Aedes heat shock promoter, Hsp70A driving dsALP1RNA. Four different mosquitocidal toxins were used for larval bioassays against this transgenic mosquito. Bioassay results show thatCry11Aa toxicity to these transgenic larvae following a heat shock decreased (4.4 fold) and Cry11Ba toxicity is slightly attenuated. But Cry4Aa and Cry4Ba toxicity to ALP1 silenced larvae is unchanged. Without heat shock, toxicity of all four toxins does not change, suggesting this heat shock promoter is heat-inducible. Notably, transgenic mosquitoes with ALP1 knockdown are about 3.7 times less resistant to Cry11Aa toxin than those with Aedes cadherin knockdown. These results demonstrate that the ALP1 is an important secondary receptor for Cry11Aa and Cry11Ba, but it might not be involved in Cry4Aa and Cry4Ba toxicity.
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Affiliation(s)
- Jianwu Chen
- Departmentof Cell Biology and Neurosciences, University of California, Riverside, CA 92521, United States.
| | - Karly Aimanova
- Departmentof Cell Biology and Neurosciences, University of California, Riverside, CA 92521, United States
| | - Sarjeet S Gill
- Departmentof Cell Biology and Neurosciences, University of California, Riverside, CA 92521, United States
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17
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Zhang Q, Hua G, Adang MJ. Effects and mechanisms of Bacillus thuringiensis crystal toxins for mosquito larvae. INSECT SCIENCE 2017; 24:714-729. [PMID: 27628909 DOI: 10.1111/1744-7917.12401] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Revised: 08/15/2016] [Accepted: 08/22/2016] [Indexed: 06/06/2023]
Abstract
Bacillus thuringiensis is a Gram-positive aerobic bacterium that produces insecticidal crystalline inclusions during sporulation phases of the mother cell. The virulence factor, known as parasporal crystals, is composed of Cry and Cyt toxins. Most Cry toxins display a common 3-domain topology. Cry toxins exert intoxication through toxin activation, receptor binding and pore formation in a suitable larval gut environment. The mosquitocidal toxins of Bt subsp. israelensis (Bti) were found to be highly active against mosquito larvae and are widely used for vector control. Bt subsp. jegathesan is another strain which possesses high potency against broad range of mosquito larvae. The present review summarizes characterized receptors for Cry toxins in mosquito larvae, and will also discuss the diversity and effects of 3-D mosquitocidal Cry toxin and the ongoing research for Cry toxin mechanisms generated from investigations of lepidopteran and dipteran larvae.
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Affiliation(s)
- Qi Zhang
- College of Plant Protection, Shenyang Agricultural University, Shenyang, China
- Department of Entomology, University of Georgia, Athens, GA, USA
| | - Gang Hua
- Department of Entomology, University of Georgia, Athens, GA, USA
| | - Michael J Adang
- Department of Entomology, University of Georgia, Athens, GA, USA
- Department of Biochemistry & Molecular Biology, University of Georgia, Athens, GA, USA
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18
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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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19
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Airs PM, Bartholomay LC. RNA Interference for Mosquito and Mosquito-Borne Disease Control. INSECTS 2017; 8:E4. [PMID: 28067782 PMCID: PMC5371932 DOI: 10.3390/insects8010004] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Revised: 12/15/2016] [Accepted: 12/21/2016] [Indexed: 11/16/2022]
Abstract
RNA interference (RNAi) is a powerful tool to silence endogenous mosquito and mosquito-borne pathogen genes in vivo. As the number of studies utilizing RNAi in basic research grows, so too does the arsenal of physiological targets that can be developed into products that interrupt mosquito life cycles and behaviors and, thereby, relieve the burden of mosquitoes on human health and well-being. As this technology becomes more viable for use in beneficial and pest insect management in agricultural settings, it is exciting to consider its role in public health entomology. Existing and burgeoning strategies for insecticide delivery could be adapted to function as RNAi trigger delivery systems and thereby expedite transformation of RNAi from the lab to the field for mosquito control. Taken together, development of RNAi-based vector and pathogen management techniques & strategies are within reach. That said, tools for successful RNAi design, studies exploring RNAi in the context of vector control, and studies demonstrating field efficacy of RNAi trigger delivery have yet to be honed and/or developed for mosquito control.
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Affiliation(s)
- Paul M Airs
- Department of Pathobiological Sciences, University of Wisconsin-Madison, Madison, WI 53706, USA.
| | - Lyric C Bartholomay
- Department of Pathobiological Sciences, University of Wisconsin-Madison, Madison, WI 53706, USA.
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20
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Sriwimol W, Aroonkesorn A, Sakdee S, Kanchanawarin C, Uchihashi T, Ando T, Angsuthanasombat C. Potential Prepore Trimer Formation by the Bacillus thuringiensis Mosquito-specific Toxin: MOLECULAR INSIGHTS INTO A CRITICAL PREREQUISITE OF MEMBRANE-BOUND MONOMERS. J Biol Chem 2015; 290:20793-20803. [PMID: 26112409 DOI: 10.1074/jbc.m114.627554] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Indexed: 12/31/2022] Open
Abstract
The insecticidal feature of the three-domain Cry δ-endotoxins from Bacillus thuringiensis is generally attributed to their capability to form oligomeric pores, causing lysis of target larval midgut cells. However, the molecular description of their oligomerization process has not been clearly defined. Here a stable prepore of the 65-kDa trypsin-activated Cry4Ba mosquito-specific toxin was established through membrane-mimetic environments by forming an ∼200-kDa octyl-β-D-glucoside micelle-induced trimer. The SDS-resistant trimer caused cytolysis to Sf9 insect cells expressing Aedes-mALP (a Cry4Ba receptor) and was more effective than a toxin monomer in membrane perturbation of calcein-loaded liposomes. A three-dimensional model of toxin trimer obtained by negative-stain EM in combination with single-particle reconstruction at ∼5 nm resolution showed a propeller-shaped structure with 3-fold symmetry. Fitting the three-dimensional reconstructed EM map with a 100-ns molecular dynamics-simulated Cry4Ba structure interacting with an octyl-β-D-glucoside micelle showed relative positioning of individual domains in the context of the trimeric complex with a major protrusion from the pore-forming domain. Moreover, high-speed atomic force microscopy imaging at nanometer resolution and a subsecond frame rate demonstrated conformational transitions from a propeller-like to a globularly shaped trimer upon lipid membrane interactions, implying prepore-to-pore conversion. Real-time trimeric arrangement of monomers associated with L-α-dimyristoylphosphatidylcholine/3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxy-1-propanesulfonic acid bicelle membranes was also envisaged by successive high-speed atomic force microscopy imaging, depicting interactions among three individual subunits toward trimer formation. Together, our data provide the first pivotal insights into the structural requirement of membrane-induced conformational changes of Cry4Ba toxin monomers for the molecular assembly of a prepore trimer capable of inserting into target membranes to generate a lytic pore.
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Affiliation(s)
- Wilaiwan Sriwimol
- Department of Clinical Chemistry, Faculty of Medical Technology, Mahidol University, Nakornpathom 73170, Thailand; Department of Bacterial Protein Toxin Research Cluster, Institute of Molecular Biosciences, Mahidol University, Nakornpathom 73170, Thailand
| | - Aratee Aroonkesorn
- Department of Bacterial Protein Toxin Research Cluster, Institute of Molecular Biosciences, Mahidol University, Nakornpathom 73170, Thailand
| | - Somsri Sakdee
- Department of Bacterial Protein Toxin Research Cluster, Institute of Molecular Biosciences, Mahidol University, Nakornpathom 73170, Thailand
| | - Chalermpol Kanchanawarin
- Laboratory of Theoretical and Computational Biophysics, Department of Physics, Faculty of Science, Kasetsart University, Bangkok 10900, Thailand
| | - Takayuki Uchihashi
- Department of Physics and Bio-AFM Frontier Research Center, Kanazawa University, Kanazawa, Ishikawa 920-1192, Japan
| | - Toshio Ando
- Department of Physics and Bio-AFM Frontier Research Center, Kanazawa University, Kanazawa, Ishikawa 920-1192, Japan
| | - Chanan Angsuthanasombat
- Department of Bacterial Protein Toxin Research Cluster, Institute of Molecular Biosciences, Mahidol University, Nakornpathom 73170, Thailand; Laboratory of Molecular Biophysics and Structural Biochemistry, Biophysics Institute for Research and Development, Bangkok 10160, Thailand.
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21
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Lee SB, Chen J, Aimanova KG, Gill SS. Aedes cadherin mediates the in vivo toxicity of the Cry11Aa toxin to Aedes aegypti. Peptides 2015; 68:140-147. [PMID: 25064814 PMCID: PMC4305047 DOI: 10.1016/j.peptides.2014.07.015] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/11/2014] [Revised: 07/07/2014] [Accepted: 07/07/2014] [Indexed: 12/16/2022]
Abstract
Cadherin plays an important role in the toxicity of Bacillus thuringiensis Cry proteins. We previously cloned a full-length cadherin from Aedes aegypti larvae and reported this protein binds Cry11Aa toxin from B. thuringiensis subsp. israelensis with high affinity, ≈16.7nM. Based on these results, we investigated if Aedes cadherin is involved in the in vivo toxicity of Cry11Aa toxin to Ae. aegypti. We established a mosquito cell line stably expressing the full-length Aedes cadherin and transgenic mosquitoes with silenced Aedes cadherin expression. Cells expressing the Aedes cadherin showed increased sensitivity to Cry11Aa toxin. Cry11Aa toxin at 400nM killed approximately 37% of the cells in 3h. Otherwise, transgenic mosquitoes with silenced Aedes cadherin expression showed increased tolerance to Cry11Aa toxin. Furthermore, cells expressing Aedes cadherin triggered Cry11Aa oligomerization. These results show the Aedes cadherin plays a pivotal role in Cry11Aa toxicity to Ae. aegypti larvae by mediating Cry11Aa oligomerization. However, since high toxicity was not obtained in cadherin-expressing cells, an additional receptor may be needed for manifestation of full toxicity. Moreover, cells expressing Aedes cadherin were sensitive to Cry4Aa and Cry11Ba, but not Cry4Ba. However transgenic mosquitoes with silenced Aedes cadherin expression showed no tolerance to Cry4Aa, Cry4Ba, and Cry11Ba toxins. These results suggest that while Aedes cadherin may mediate Cry4Aa and Cry11Ba toxicity, this cadherin but is not the main receptor of Cry4Aa, Cry4Ba and Cry11Ba toxin in Ae. aegypti.
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Affiliation(s)
- Su-Bum Lee
- Environmental Toxicology graduate program, University of California, Riverside, CA, 92521, USA
| | - Jianwu Chen
- Department of Cell Biology and Neuroscience, University of California, Riverside, CA, 92521, USA
| | - Karlygash G. Aimanova
- Department of Cell Biology and Neuroscience, University of California, Riverside, CA, 92521, USA
| | - Sarjeet S. Gill
- Environmental Toxicology graduate program, University of California, Riverside, CA, 92521, USA
- Department of Cell Biology and Neuroscience, University of California, Riverside, CA, 92521, USA
- Corresponding author: . Tel: 951-827-4621/3547
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Zhang Q, Hua G, Adang MJ. Chitosan/DsiRNA nanoparticle targeting identifies AgCad1 cadherin in Anopheles gambiae larvae as an in vivo receptor of Cry11Ba toxin of Bacillus thuringiensis subsp. jegathesan. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2015; 60:33-38. [PMID: 25758367 DOI: 10.1016/j.ibmb.2015.03.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Revised: 02/18/2015] [Accepted: 03/01/2015] [Indexed: 06/04/2023]
Abstract
The Cry11Ba protein of Bacillus thuringiensis subsp. jegathesan crystals has uniquely high toxicity against a spectrum of mosquito species. The high potency of Cry11Ba against Anopheles gambiae is caused by recognition of multiple midgut proteins including glycosyl phosphatidylinositol-anchored alkaline phosphatase AgALP1, aminopeptidase AgAPN2, α-amylase AgAmy1 and α-glucosidase Agm3 that bind Cry11Ba with high affinity and function as putative receptors. The cadherin AgCad2 in An. gambiae larvae also binds Cry11Ba with high affinity (Kd = 12 nM) and is considered a putative receptor, while cadherin AgCad1 bound Cry11Ba with low affinity (Kd = 766 nM), a property not supportive for a Cry11Ba receptor role. Here, we show the in vivo involvement of AgCad1 in Cry11Ba toxicity in An. gambiae larvae using chitosan/DsiRNA nanoparticles to inhibit AgCad expression in larvae. Cry11Ba was significantly less toxic to AgCad1-silenced larvae than to control larvae. Because AgCad1 was co-suppressed by AgCad2 DsRNAi, the involvement of AgCad2 in Cry11Ba toxicity could not be ascertained. The ratio of AgCad1:AgCad2 transcript level is 36:1 for gut tissue in 4th instar larvae. Silencing AgCad expression had no effect on transcript levels of other binding receptors of Cry11Ba. We conclude that AgCad1 and possibly AgCad2 in An. gambiae larvae are functional receptors of Cry11Ba toxin in vivo.
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Affiliation(s)
- Qi Zhang
- Department of Entomology, University of Georgia, Athens, GA 30602-2603, USA
| | - Gang Hua
- Department of Entomology, University of Georgia, Athens, GA 30602-2603, USA
| | - Michael J Adang
- Department of Entomology, University of Georgia, Athens, GA 30602-2603, USA; Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602-2603, USA.
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A toxin-binding alkaline phosphatase fragment synergizes Bt toxin Cry1Ac against susceptible and resistant Helicoverpa armigera. PLoS One 2015; 10:e0126288. [PMID: 25885820 PMCID: PMC4401514 DOI: 10.1371/journal.pone.0126288] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Accepted: 03/31/2015] [Indexed: 11/19/2022] Open
Abstract
Evolution of resistance by insects threatens the continued success of pest control using insecticidal crystal (Cry) proteins from the bacterium Bacillus thuringiensis (Bt) in sprays and transgenic plants. In this study, laboratory selection with Cry1Ac yielded five strains of cotton bollworm, Helicoverpa armigera, with resistance ratios at the median lethal concentration (LC50) of activated Cry1Ac ranging from 22 to 1700. Reduced activity and reduced transcription of an alkaline phosphatase protein that binds Cry1Ac was associated with resistance to Cry1Ac in the four most resistant strains. A Cry1Ac-binding fragment of alkaline phosphatase from H. armigera (HaALP1f) was not toxic by itself, but it increased mortality caused by Cry1Ac in a susceptible strain and in all five resistant strains. Although synergism of Bt toxins against susceptible insects by toxin-binding fragments of cadherin and aminopeptidase N has been reported previously, the results here provide the first evidence of synergism of a Bt toxin by a toxin-binding fragment of alkaline phosphatase. The results here also provide the first evidence of synergism of a Bt toxin by any toxin-binding peptide against resistant insects.
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Lee SB, Aimanova KG, Gill SS. Alkaline phosphatases and aminopeptidases are altered in a Cry11Aa resistant strain of Aedes aegypti. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2014; 54:112-121. [PMID: 25242559 PMCID: PMC4254116 DOI: 10.1016/j.ibmb.2014.09.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Revised: 09/10/2014] [Accepted: 09/13/2014] [Indexed: 06/01/2023]
Abstract
Bacillus thuringiensis subsp. israelensis (Bti) is widely used for the biological control of mosquito populations. However, the mechanism of Bti toxins is still not fully understood. To further elucidate the mechanism of Bti toxins, we developed an Aedes aegypti resistant strain that shows high-level resistance to Cry11Aa toxin. After 27 selections with Cry11Aa toxin, the larvae showed a 124-fold resistance ratio for Cry11Aa (strain G30). G30 larvae showed cross-resistance to Cry4Aa (66-fold resistance), less to Cry4Ba (13-fold), but not to Cry11Ba (2-fold). Midguts from these resistant larvae did not show detectable difference in the processing of the Cry11Aa toxin compared to that in susceptible larvae (WT). Brush border membrane vesicles (BBMV) from resistant larvae bound slightly less Cry11Aa compared to WT BBMV. To identify potential proteins associated with Cry11A resistance, not only transcript changes in the larval midgut were analyzed using Illumina sequencing and qPCR, but alterations of previously identified receptor proteins were investigated using immunoblots. The transcripts of 375 genes were significantly increased and those of 208 genes were down regulated in the resistant larvae midgut compared to the WT. None of the transcripts for previously identified receptors of Cry11Aa (Aedes cadherin, ALP1, APN1, and APN2) were altered in these analyses. The genes for the identified functional receptors in resistant larvae midgut did not contain any mutation in their sequences nor was there any change in their transcript expression levels compared to WT. However, ALP proteins were expressed at reduced levels (∼ 40%) in the resistant strain BBMV. APN proteins and their activity were also slightly reduced in resistance strain. The transcript levels of ALPs (AAEL013330 and AAEL015070) and APNs (AAEL008158, AAEL008162) were significantly reduced. These results strongly suggest that ALPs and APNs could be associated with Cry11Aa resistance in Ae. aegypti.
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Affiliation(s)
- Su-Bum Lee
- Environmental Toxicology Graduate Program, University of California, Riverside, CA 92521, USA; Department of Cell Biology and Neuroscience, University of California, Riverside, CA 92521, USA
| | - Karlygash G Aimanova
- Department of Cell Biology and Neuroscience, University of California, Riverside, CA 92521, USA
| | - Sarjeet S Gill
- Environmental Toxicology Graduate Program, University of California, Riverside, CA 92521, USA; Department of Cell Biology and Neuroscience, University of California, Riverside, CA 92521, USA.
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Bacillus thuringiensis Cry1A toxins are versatile proteins with multiple modes of action: two distinct pre-pores are involved in toxicity. Biochem J 2014; 459:383-96. [PMID: 24456341 PMCID: PMC3969221 DOI: 10.1042/bj20131408] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Cry proteins from Bacillus thuringiensis are insecticidal PFTs (pore-forming toxins). In the present study, we show that two distinct functional pre-pores of Cry1Ab are formed after binding of the protoxin or the protease-activated toxin to the cadherin receptor, but before membrane insertion. Both pre-pores actively induce pore formation, although with different characteristics, and contribute to the insecticidal activity. We also analysed the oligomerization of the mutant Cry1AbMod protein. This mutant kills different insect populations that are resistant to Cry toxins, but lost potency against susceptible insects. We found that the Cry1AbMod-protoxin efficiently induces oligomerization, but not the activated Cry1AbMod-toxin, explaining the loss of potency of Cry1AbMod against susceptible insects. These data are relevant for the future control of insects resistant to Cry proteins. Our data support the pore-formation model involving sequential interaction with different midgut proteins, leading to pore formation in the target membrane. We propose that not only different insect targets could have different receptors, but also different midgut proteases that would influence the rate of protoxin/toxin activation. It is possible that the two pre-pore structures could have been selected for in evolution, since they have differential roles in toxicity against selected targets, increasing their range of action. These data assign a functional role for the protoxin fragment of Cry PFTs that was not understood previously. Most PFTs produced by other bacteria are secreted as protoxins that require activation before oligomerization, to finally form a pore. Thus different pre-pores could be also part of the general mechanism of action of other PFTs. Two distinct functional pre-pore oligomers of the Cry1Ab insecticidal toxin are formed before membrane insertion. These oligomers are formed after binding of either the protoxin or the protease-activated toxin to the cadherin receptor. Both pre-pores have different characteristics and contribute to insecticidal activity.
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Bacillus thuringiensis subsp. israelensis and its dipteran-specific toxins. Toxins (Basel) 2014; 6:1222-43. [PMID: 24686769 PMCID: PMC4014730 DOI: 10.3390/toxins6041222] [Citation(s) in RCA: 124] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Revised: 03/10/2014] [Accepted: 03/14/2014] [Indexed: 01/05/2023] Open
Abstract
Bacillus thuringiensis subsp. israelensis (Bti) is the first Bacillus thuringiensis to be found and used as an effective biological control agent against larvae of many mosquito and black fly species around the world. Its larvicidal activity resides in four major (of 134, 128, 72 and 27 kDa) and at least two minor (of 78 and 29 kDa) polypeptides encoded respectively by cry4Aa, cry4Ba, cry11Aa, cyt1Aa, cry10Aa and cyt2Ba, all mapped on the 128 kb plasmid known as pBtoxis. These six δ-endotoxins form a complex parasporal crystalline body with remarkably high, specific and different toxicities to Aedes, Culex and Anopheles larvae. Cry toxins are composed of three domains (perforating domain I and receptor binding II and III) and create cation-selective channels, whereas Cyts are composed of one domain that acts as well as a detergent-like membrane perforator. Despite the low toxicities of Cyt1Aa and Cyt2Ba alone against exposed larvae, they are highly synergistic with the Cry toxins and hence their combinations prevent emergence of resistance in the targets. The lack of significant levels of resistance in field mosquito populations treated for decades with Bti-bioinsecticide suggests that this bacterium will be an effective biocontrol agent for years to come.
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Zúñiga-Navarrete F, Gómez I, Peña G, Bravo A, Soberón M. A Tenebrio molitor GPI-anchored alkaline phosphatase is involved in binding of Bacillus thuringiensis Cry3Aa to brush border membrane vesicles. Peptides 2013; 41:81-6. [PMID: 22743140 DOI: 10.1016/j.peptides.2012.05.019] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2012] [Revised: 05/23/2012] [Accepted: 05/30/2012] [Indexed: 01/02/2023]
Abstract
Bacillus thuringiensis Cry toxins recognizes their target cells in part by the binding to glycosyl-phosphatidyl-inositol (GPI) anchored proteins such as aminopeptidase-N (APN) or alkaline phosphatases (ALP). Treatment of Tenebrio molitor brush border membrane vesicles (BBMV) with phospholipase C that cleaves out GPI-anchored proteins from the membranes, showed that GPI-anchored proteins are involved in binding of Cry3Aa toxin to BBMV. A 68 kDa GPI-anchored ALP was shown to bind Cry3Aa by toxin overlay assays. The 68 kDa GPI-anchored ALP was preferentially expressed in early instar larvae in comparison to late instar larvae. Our work shows for the first time that GPI-anchored ALP is important for Cry3Aa binding to T. molitor BBMV suggesting that the mode of action of Cry toxins is conserved in different insect orders.
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Affiliation(s)
- Fernando Zúñiga-Navarrete
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca 62250, Morelos, Mexico
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Hua G, Zhang Q, Zhang R, Abdullah AM, Linser PJ, Adang MJ. AgCad2 cadherin in Anopheles gambiae larvae is a putative receptor of Cry11Ba toxin of Bacillus thuringiensis subsp. jegathesan. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2013; 43:153-161. [PMID: 23231770 DOI: 10.1016/j.ibmb.2012.11.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Revised: 11/22/2012] [Accepted: 11/30/2012] [Indexed: 06/01/2023]
Abstract
In an effort to study the mode of action of Cry11Ba, we identified toxin binding proteins in Anopheles gambiae larval midgut and investigated their receptor roles. Previously, an aminopeptidase (AgAPN2) and an alkaline phosphatase (AgALP1) were identified as receptors for Cry11Ba toxin in A. gambiae. However, an A. gambiae cadherin (AgCad1) that bound Cry11Ba with low affinity (K(d) = 766 nM) did not support a receptor role of AgCad1 for Cry11Ba. Here, we studied a second A. gambiae cadherin (AgCad2) that shares 14% identity to AgCad1. Immunohistochemical study showed that the protein is localized on A. gambiae larval midgut apical membranes. Its cDNA was cloned and the protein was analyzed as a transmembrane protein containing 14 cadherin repeats. An Escherichia coli expressed CR14MPED fragment of AgCad2 bound Cry11Ba with high affinity (K(d) = 11.8 nM), blocked Cry11Ba binding to A. gambiae brush border vesicles and reduced Cry11Ba toxicity in bioassays. Its binding to Cry11Ba could be completely competed off by AgCad1, but only partially competed by AgALP1. The results are evidence that AgCad2 may function as a receptor for Cry11Ba in A. gambiae larvae.
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Affiliation(s)
- Gang Hua
- Department of Entomology, University of Georgia, Athens, GA 30602-2603, USA
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Abstract
Many electrical properties of insect larval guts have been studied, but their importance for toxicity of the Cry-type toxins has never been reported in the literature. In the present work, we observed potential-dependent permeabilization of plasma membrane by several polycationic peptides derived from the Cry11Bb protoxin. The peptide BTM-P1d, all D-type amino acid analogue of the earlier reported peptide BTM-P1, demonstrated high membrane-permeabilizing activity in experiments with isolated rat liver mitochondria, RBC (red blood cells) and mitochondria in homogenates of Aedes aegypti larval guts. Two larger peptides, BTM-P2 and BTM-P3, as well as the Cry11Bb protoxin treated with the protease extract of mosquito larval guts showed similar effects. Only protease-resistant BTM-P1d, in comparison with other peptides, displayed A. aegypti larval toxicity. Taking into account the potential-dependent mechanism of membrane permeabilization by studied fragments of the Cry11Bb protoxin and the literature data related to the distribution of membrane and transepithelial potentials in the A. aegypti larval midgut, we suggest an electrical hypothesis of toxicity of the Cry toxins for mosquito larvae. According to this hypothesis, the electrical field distribution is one of the factors determining the midgut region most susceptible for insertion of activated toxins into the plasma membrane to form pores. In addition, potential-dependent penetration of short active toxin fragments into the epithelial cells could induce permeabilization of mitochondria and subsequent apoptosis or necrosis.
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Pardo-López L, Soberón M, Bravo A. Bacillus thuringiensisinsecticidal three-domain Cry toxins: mode of action, insect resistance and consequences for crop protection. FEMS Microbiol Rev 2013; 37:3-22. [DOI: 10.1111/j.1574-6976.2012.00341.x] [Citation(s) in RCA: 473] [Impact Index Per Article: 43.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Revised: 04/10/2012] [Accepted: 04/16/2012] [Indexed: 11/30/2022] Open
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Jiménez AI, Reyes EZ, Cancino-Rodezno A, Bedoya-Pérez LP, Caballero-Flores GG, Muriel-Millan LF, Likitvivatanavong S, Gill SS, Bravo A, Soberón M. Aedes aegypti alkaline phosphatase ALP1 is a functional receptor of Bacillus thuringiensis Cry4Ba and Cry11Aa toxins. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2012; 42:683-9. [PMID: 22728570 PMCID: PMC3416946 DOI: 10.1016/j.ibmb.2012.06.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2012] [Revised: 05/31/2012] [Accepted: 06/04/2012] [Indexed: 05/26/2023]
Abstract
Bacillus thuringiensis subs. israelensis produces at least three Cry toxins (Cry4Aa, Cry4Ba, and Cry11Aa) that are active against Aedes aegypti larvae. Previous work characterized a GPI-anchored alkaline phosphatase (ALP1) as a Cry11Aa binding molecule from the gut of A. aegypti larvae. We show here that Cry4Ba binds ALP1, and that the binding and toxicity of Cry4Ba mutants located in loop 2 of domain II is correlated. Also, we analyzed the contribution of ALP1 toward the toxicity of Cry4Ba and Cry11Aa toxins by silencing the expression of this protein though RNAi. Efficient silencing of ALP1 was demonstrated by real-time quantitative PCR (qPCR) and Western blot. ALP1 silenced larvae showed tolerance to both Cry4Ba and Cry11Aa although the silenced larvae were more tolerant to Cry11Aa in comparison to Cry4Ba. Our results demonstrate that ALP1 is a functional receptor that plays an important role in the toxicity of the Cry4Ba and Cry11Aa proteins.
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Affiliation(s)
- Alan I. Jiménez
- Instituto de Biotecnología, Universidad Nacional Autónoma de México. Apdo. postal 510-3, Cuernavaca 62250, Morelos, Mexico
| | - Esmeralda Z. Reyes
- Instituto de Biotecnología, Universidad Nacional Autónoma de México. Apdo. postal 510-3, Cuernavaca 62250, Morelos, Mexico
| | - Angeles Cancino-Rodezno
- Instituto de Biotecnología, Universidad Nacional Autónoma de México. Apdo. postal 510-3, Cuernavaca 62250, Morelos, Mexico
| | - Leidy P. Bedoya-Pérez
- Instituto de Biotecnología, Universidad Nacional Autónoma de México. Apdo. postal 510-3, Cuernavaca 62250, Morelos, Mexico
| | - Gustavo G. Caballero-Flores
- Instituto de Biotecnología, Universidad Nacional Autónoma de México. Apdo. postal 510-3, Cuernavaca 62250, Morelos, Mexico
| | - Luis F. Muriel-Millan
- Instituto de Biotecnología, Universidad Nacional Autónoma de México. Apdo. postal 510-3, Cuernavaca 62250, Morelos, Mexico
| | | | - Sarjeet S. Gill
- Department of Cell Biology and Neuroscience, University of California, Riverside, CA 92506
| | - 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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