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Cotto-Rivera RO, Joya N, Hernández-Martínez P, Ferré J, Wang P. Downregulation of APN1 and ABCC2 mutation in Bt Cry1Ac-resistant Trichoplusia ni are genetically independent. Appl Environ Microbiol 2024:e0074224. [PMID: 39291983 DOI: 10.1128/aem.00742-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2024] [Accepted: 08/30/2024] [Indexed: 09/19/2024] Open
Abstract
The resistance to the insecticidal protein Cry1Ac from the bacterium Bacillus thuringiensis (Bt) in the cabbage looper, Trichoplusia ni, has previously been identified to be associated with a frameshift mutation in the ABC transporter ABCC2 gene and with altered expression of the aminopeptidase N (APN) genes APN1 and APN6, shown as missing of the 110-kDa APN1 (phenotype APN1¯) in larval midgut brush border membrane vesicles (BBMV). In this study, genetic linkage analysis identified that the APN1¯ phenotype and the ABCC2 mutation in Cry1Ac-resistant T. ni segregated independently, although they were always associated under Cry1Ac selection. The ABCC2 mutation and APN1¯ phenotype were separated into two T. ni strains respectively. Bioassays of the T. ni strains with Cry1Ac determined that the T. ni with the APN1¯ phenotype showed a low level resistance to Cry1Ac (3.5-fold), and the associated resistance is incompletely dominant in the background of the ABCC2 mutation. Whereas the ABCC2 mutation-associated resistance to Cry1Ac is at a moderate level, and the resistance is incompletely recessive in the genetic background of downregulated APN1. Analysis of Cry1Ac binding to larval midgut BBMV indicated that the midgut in larvae with the APN1¯ phenotype had reduced binding affinity for Cry1Ac, but the number of binding sites remained unchanged, and the midgut in larvae with the ABCC2 mutation had both reduced binding affinity and reduced number of binding sites for Cry1Ac. The reduced Cry1Ac binding to BBMV from larvae with the ABCC2 mutation or APN1¯ phenotype correlated with the lower levels of resistance.IMPORTANCEThe soil bacterium Bacillus thuringiensis (Bt) is an important insect pathogen used as a bioinsecticide for pest control. Bt genes coding for insecticidal proteins are the primary transgenes engineered into transgenic crops (Bt crops) to confer insect resistance. However, the evolution of resistance to Bt proteins in insect populations in response to exposure to Bt threatens the sustainable application of Bt biotechnology. Cry1Ac is a major insecticidal toxin utilized for insect control. Genetic mechanisms of insect resistance to Cry1Ac are complex and require to be better understood. The resistance to Cry1Ac in Trichoplusia ni is associated with a mutation in the ABCC2 gene and also associated with the APN expression phenotype APN1¯. This study identified the genetic independence of the APN1¯ phenotype from the ABCC2 mutation and isolated and analyzed the ABCC2 mutation-associated and APN1¯ phenotype-associated resistance traits in T. ni to provide new insights into the genetic mechanisms of Cry1Ac resistance in insects.
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Affiliation(s)
| | - Noelia Joya
- Department of Genetics, Instituto Universitario de Biotecnología y Biomedicina (BIOTECMED), Universitat de València, Burjassot, Spain
| | - Patricia Hernández-Martínez
- Department of Genetics, Instituto Universitario de Biotecnología y Biomedicina (BIOTECMED), Universitat de València, Burjassot, Spain
| | - Juan Ferré
- Department of Genetics, Instituto Universitario de Biotecnología y Biomedicina (BIOTECMED), Universitat de València, Burjassot, Spain
| | - Ping Wang
- Department of Entomology, Cornell University, Geneva, New York, USA
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Resistance of Cabbage Loopers to Bacillus thuringiensis (Bt) Toxin Cry1F and to Dual-Bt Toxin WideStrike Cotton Plants. Appl Environ Microbiol 2022; 88:e0119422. [PMID: 36200769 PMCID: PMC9599322 DOI: 10.1128/aem.01194-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Cry proteins from Bacillus thuringiensis (Bt) are major insecticidal toxins in formulated Bt sprays and are expressed in genetically engineered Bt crops for insect pest control. However, the widespread application of Bt toxins in the field imposes strong selection pressure on target insects, leading to the evolution of insect resistance to the Bt toxins. Identification and understanding of mechanisms of insect resistance to Bt toxins are an important approach for dissecting the modes of action of Bt toxins and providing knowledge necessary for the development of resistance management technologies. In this study, cabbage looper (Trichoplusia ni) strains resistant to the transgenic dual-Bt toxin WideStrike cotton plants, which express Bt toxins Cry1Ac and Cry1F, were selected from T. ni strains resistant to the Bt formulation Bt-DiPel. The WideStrike-resistant T. ni larvae were confirmed to be resistant to both Bt toxins Cry1Ac and Cry1F. From the WideStrike-resistant T. ni, the Cry1F resistance trait was further isolated to establish a T. ni strain resistant to Cry1F only. The levels of Cry1F resistance in the WideStrike-resistant and the Cry1F-resistant strains were determined, and the inheritance of the Cry1F-resistant trait in the two strains was characterized. Genetic association analysis of the Cry1F resistance trait indicated that the Cry1F resistance in T. ni isolated in this study is not shared with the Cry1Ac resistance mechanism nor is it associated with a mutation in the ABCC2 gene, as has so far been reported in Cry1F-resistant insects. IMPORTANCE Insecticidal toxins from Bacillus thuringiensis (Bt) are highly effective for insect control in agriculture. However, the widespread application of Bt toxins exerts strong selection for Bt resistance in insect populations. The continuing success of Bt biotechnology for pest control requires the identification of resistance and understanding of the mechanisms of resistance to Bt toxins. Cry1F is an important Bt toxin used in transgenic cotton, maize, and soybean varieties adopted widely for insect control. To understand the mode of action of Cry1F and mechanisms of Cry1F resistance in insects, it is important to identify Cry1F-specific resistance and the resistance mechanisms. In this study, Trichoplusia ni strains resistant to commercial "WideStrike" cotton plants that express Bt toxins Cry1Ac and Cry1F were selected, and a Cry1F-specific resistant strain was isolated. The isolation of the novel Cry1F-specific resistance in the T. ni provided an invaluable biological system to discover a Cry1F-specific novel resistance mechanism.
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Ma X, Shao E, Chen W, Cotto-Rivera RO, Yang X, Kain W, Fei Z, Wang P. Bt Cry1Ac resistance in Trichoplusia ni is conferred by multi-gene mutations. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2022; 140:103678. [PMID: 34780898 DOI: 10.1016/j.ibmb.2021.103678] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Revised: 10/28/2021] [Accepted: 11/03/2021] [Indexed: 06/13/2023]
Abstract
The three-domain Cry toxin Cry1Ac from Bacillus thuringiensis (Bt) is an important insecticidal toxin in Bt sprays and has been used in transgenic Bt-crops to confer insect resistance. The cabbage looper, Trichoplusia ni, has developed resistance to Bt sprays in commercial greenhouses, and the resistance to Cry1Ac has been previously identified to be associated with altered expression of the APN1 and APN6 genes and be genetically linked to a locus on chromosome 15. In this study, the Cry1Ac resistance locus in T. ni was further finely mapped, and the specific Cry1Ac resistance-conferring mutation in the resistance locus was identified to be a 4 bp frameshift insertion in the ABCC2 gene by whole genome resequencing, midgut transcriptome analysis, candidate gene cDNA sequencing and mutation site genomic DNA sequencing. By CRISPR/Cas9 mutagenesis, a series of ABCC2 and ABCC3 mutant T. ni strains were generated, and the role of ABCC2 in the toxicity of Cry1Ac in T. ni was confirmed. The results from this study also showed that knockout of ABCC2 in T. ni conferred resistance to Cry1Ac at a level lower than that in the greenhouse-derived resistant T. ni strain and that the Cry1Ac resistance-associated alteration of APN1 and APN6 expression was independent of ABCC2 gene mutations, indicating that the altered expression of APN1 and APN6 was controlled by another gene mutation in Cry1Ac resistant T. ni. Furthermore, T. ni larval bioassays showed that the level of Cry1Ac resistance in F1 families from reciprocal crosses of the Cry1Ac resistant strain with an ABCC2 knockout CRISPR strain was significantly higher than that in ABCC2 knockout strain, indicating the presence of additional Cry1Ac resistance-conferring mutation(s) in the Cry1Ac resistant strain. Therefore, the resistance to Cry1Ac in T. ni is conferred by a mutation in ABCC2 and an additional mutation (or mutations) which leads to altered expression of APN1 and APN6. The additional Cry1Ac resistance mutation or mutations remain to be identified.
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Affiliation(s)
- Xiaoli Ma
- Department of Entomology, Cornell University, Geneva, NY, 14456, USA
| | - Ensi Shao
- Department of Entomology, Cornell University, Geneva, NY, 14456, USA
| | - Wenbo Chen
- Boyce Thompson Institute, Ithaca, NY, 14853, USA
| | | | - Xiaowei Yang
- Department of Entomology, Cornell University, Geneva, NY, 14456, USA
| | - Wendy Kain
- Department of Entomology, Cornell University, Geneva, NY, 14456, USA
| | - Zhangjun Fei
- Boyce Thompson Institute, Ithaca, NY, 14853, USA; USDA-Agricultural Research Service, Robert W. Holley Center for Agriculture and Health, Ithaca, NY, 14853, USA
| | - Ping Wang
- Department of Entomology, Cornell University, Geneva, NY, 14456, USA.
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Liu L, Li Z, Luo X, Zhang X, Chou SH, Wang J, He J. Which Is Stronger? A Continuing Battle Between Cry Toxins and Insects. Front Microbiol 2021; 12:665101. [PMID: 34140940 PMCID: PMC8203666 DOI: 10.3389/fmicb.2021.665101] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Accepted: 04/20/2021] [Indexed: 12/20/2022] Open
Abstract
In this article, we review the latest works on the insecticidal mechanisms of Bacillus thuringiensis Cry toxins and the resistance mechanisms of insects against Cry toxins. Currently, there are two models of insecticidal mechanisms for Cry toxins, namely, the sequential binding model and the signaling pathway model. In the sequential binding model, Cry toxins are activated to bind to their cognate receptors in the mid-intestinal epithelial cell membrane, such as the glycophosphatidylinositol (GPI)-anchored aminopeptidases-N (APNs), alkaline phosphatases (ALPs), cadherins, and ABC transporters, to form pores that elicit cell lysis, while in the signaling pathway model, the activated Cry toxins first bind to the cadherin receptor, triggering an extensive cell signaling cascade to induce cell apoptosis. However, these two models cannot seem to fully describe the complexity of the insecticidal process of Cry toxins, and new models are required. Regarding the resistance mechanism against Cry toxins, the main method insects employed is to reduce the effective binding of Cry toxins to their cognate cell membrane receptors by gene mutations, or to reduce the expression levels of the corresponding receptors by trans-regulation. Moreover, the epigenetic mechanisms, host intestinal microbiota, and detoxification enzymes also play significant roles in the insects' resistance against Cry toxins. Today, high-throughput sequencing technologies like transcriptomics, proteomics, and metagenomics are powerful weapons for studying the insecticidal mechanisms of Cry toxins and the resistance mechanisms of insects. We believe that this review shall shed some light on the interactions between Cry toxins and insects, which can further facilitate the development and utilization of Cry toxins.
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Affiliation(s)
- Lu Liu
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Zhou Li
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Xing Luo
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Xia Zhang
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China.,Department of Molecular Biology, Qingdao Vland Biotech Inc., Qingdao, China
| | - Shan-Ho Chou
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China
| | - Jieping Wang
- Agricultural Bioresources Institute, Fujian Academy of Agricultural Sciences, Fuzhou, China
| | - Jin He
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China
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The Essential and Enigmatic Role of ABC Transporters in Bt Resistance of Noctuids and Other Insect Pests of Agriculture. INSECTS 2021; 12:insects12050389. [PMID: 33924857 PMCID: PMC8145640 DOI: 10.3390/insects12050389] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Revised: 04/25/2021] [Accepted: 04/26/2021] [Indexed: 11/18/2022]
Abstract
Simple Summary The insect family, Noctuidae, contains some of the most damaging pests of agriculture, including bollworms, budworms, and armyworms. Transgenic cotton and maize expressing Cry-type insecticidal proteins from Bacillus thuringiensis (Bt) are protected from such pests and greatly reduce the need for chemical insecticides. However, evolution of Bt resistance in the insects threatens the sustainability of this environmentally beneficial pest control strategy. Understanding the interaction between Bt toxins and their targets in the insect midgut is necessary to evaluate the risk of resistance evolution. ABC transporters, which in eukaryotes typically expel small molecules from cells, have recently been proposed as a target for the pore-forming Cry toxins. Here we review the literature surrounding this hypothesis in noctuids and other insects. Appreciation of the critical role of ABC transporters will be useful in discovering counterstrategies to resistance, which is already evolving in some field populations of noctuids and other insects. Abstract In the last ten years, ABC transporters have emerged as unexpected yet significant contributors to pest resistance to insecticidal pore-forming proteins from Bacillus thuringiensis (Bt). Evidence includes the presence of mutations in resistant insects, heterologous expression to probe interactions with the three-domain Cry toxins, and CRISPR/Cas9 knockouts. Yet the mechanisms by which ABC transporters facilitate pore formation remain obscure. The three major classes of Cry toxins used in agriculture have been found to target the three major classes of ABC transporters, which requires a mechanistic explanation. Many other families of bacterial pore-forming toxins exhibit conformational changes in their mode of action, which are not yet described for the Cry toxins. Three-dimensional structures of the relevant ABC transporters, the multimeric pore in the membrane, and other proteins that assist in the process are required to test the hypothesis that the ATP-switch mechanism provides a motive force that drives Cry toxins into the membrane. Knowledge of the mechanism of pore insertion will be required to combat the resistance that is now evolving in field populations of insects, including noctuids.
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Jurat-Fuentes JL, Heckel DG, Ferré J. Mechanisms of Resistance to Insecticidal Proteins from Bacillus thuringiensis. ANNUAL REVIEW OF ENTOMOLOGY 2021; 66:121-140. [PMID: 33417820 DOI: 10.1146/annurev-ento-052620-073348] [Citation(s) in RCA: 119] [Impact Index Per Article: 39.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Insecticidal proteins from the bacterium Bacillus thuringiensis (Bt) are used in sprayable formulations or produced in transgenic crops as the most successful alternatives to synthetic pesticides. The most relevant threat to sustainability of Bt insecticidal proteins (toxins) is the evolution of resistance in target pests. To date, high-level resistance to Bt sprays has been limited to one species in the field and another in commercial greenhouses. In contrast, there are currently seven lepidopteran and one coleopteran species that have evolved practical resistance to transgenic plants producing insecticidal Bt proteins. In this article, we present a review of the current knowledge on mechanisms of resistance to Bt toxins, with emphasis on key resistance genes and field-evolved resistance, to support improvement of Bt technology and its sustainability.
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Affiliation(s)
- Juan Luis Jurat-Fuentes
- Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, Tennessee 37996, USA;
| | - David G Heckel
- Department of Entomology, Max Planck Institute for Chemical Ecology, Jena 07745, Germany;
| | - Juan Ferré
- ERI of Biotechnology and Biomedicine (BIOTECMED), Universitat de València, Burjassot 46100, Spain;
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Wang S, Wang P. Functional redundancy of structural proteins of the peritrophic membrane in Trichoplusia ni. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2020; 125:103456. [PMID: 32814147 DOI: 10.1016/j.ibmb.2020.103456] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2020] [Revised: 08/08/2020] [Accepted: 08/10/2020] [Indexed: 06/11/2023]
Abstract
The peritrophic membrane (or peritrophic matrix) (PM) in insects is formed by binding of PM proteins with multiple chitin binding domains (CBDs) to chitin fibrils. Multi-CBD chitin binding proteins (CBPs) and the insect intestinal mucin (IIM) are major PM structural proteins. To understand the biochemical and physiological role of IIM in structural formation and physiological function of the PM, Trichoplusia ni mutant strains lacking IIM were generated by CRISPR/Cas9 mutagenesis. The mutant T. ni larvae were confirmed to lack IIM, but PM formation was observed as in wild type larvae and lacking IIM in the PM did not result in changes of protease activities in the larval midgut. Larval growth and development of the mutant strains were similar to the wild type strain on artificial diet and cabbage leaves, but had a decreased survival in the 5th instar. The larvae of the mutant strains with the PM formed without IIM did not have a change of susceptibility to the infection of the baculovirus AcMNPV and the Bacillus thuringiensis (Bt) formulation Dipel, to the toxicity of the Bt toxins Cry1Ac and Cry2Ab and the chemical insecticide sodium aluminofluoride. Treatment of the mutant T. ni larvae with Calcofluor reduced the larval susceptibility to the toxicity of Bt Cry1Ac, as similarly observed in the wild type larvae. Overall, in the mutant T. ni larvae, the PM was formed without IIM and the lacking of IIM in the PM did not drastically impact the performance of larvae on diet or cabbage leaves under the laboratory conditions.
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Affiliation(s)
- Shaohua Wang
- Department of Entomology, Cornell University, Geneva, NY, 14456, USA; School of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou, China
| | - Ping Wang
- Department of Entomology, Cornell University, Geneva, NY, 14456, USA.
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Tabashnik BE, Carrière Y. Evaluating Cross-resistance Between Vip and Cry Toxins of Bacillus thuringiensis. JOURNAL OF ECONOMIC ENTOMOLOGY 2020; 113:553-561. [PMID: 31821498 DOI: 10.1093/jee/toz308] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Indexed: 05/27/2023]
Abstract
Crops genetically engineered to produce insecticidal proteins from the bacterium Bacillus thuringiensis (Bt) have revolutionized control of some major pests. Some recently introduced Bt crops make Vip3Aa, a vegetative insecticidal protein (Vip), which reportedly does not share binding sites or structural homology with the crystalline (Cry) proteins of Bt used widely in transgenic crops for more than two decades. Field-evolved resistance to Bt crops with practical consequences for pest control includes 21 cases that collectively reduce the efficacy of nine Cry proteins, but such practical resistance has not been reported yet for any Vip. Here, we review previously published data to evaluate cross-resistance between Vip and Cry toxins. We analyzed 31 cases based on 48 observations, with each case based on one to five observations assessing cross-resistance from pairwise comparisons between 21 resistant strains and 13 related susceptible strains of eight species of lepidopteran pests. Confirming results from previous analyses of smaller data sets, we found weak, statistically significant cross-resistance between Vip3 and Cry1 toxins, with a mean of 1.5-fold cross-resistance in 21 cases (range: 0.30-4.6-fold). Conversely, we did not detect significant positive cross-resistance between Vip3 toxins and Cry2Ab. Distinguishing between weak, significant cross-resistance, and no cross-resistance may be useful for better understanding mechanisms of resistance and effectively managing pest resistance to Bt crops.
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Affiliation(s)
| | - Yves Carrière
- Department of Entomology, University of Arizona, Tucson, AZ
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Wei J, Zhang Y, An S. The progress in insect cross-resistance among Bacillus thuringiensis toxins. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2019; 102:e21547. [PMID: 30864250 DOI: 10.1002/arch.21547] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Revised: 02/27/2019] [Accepted: 02/28/2019] [Indexed: 06/09/2023]
Abstract
Bt crop pyramids produce two or more Bt proteins active to broaden the spectrum of action and to delay the development of resistance in exposed insect populations. The cross-resistance between Bt toxins is a vital restriction factor for Bt crop pyramids, which may reduce the effect of pyramid strategy. In this review, the status of the cross-resistance among more than 20 Bt toxins that are most commonly used against 13 insect pests was analyzed. The potential mechanisms of cross-resistance are discussed. The corresponding measures, including pyramid RNA interference and Bt toxin, "high dose/refuge," and so on are advised to be taken for adopting the pyramided strategy to delay the Bt evolution of resistance and control the target pest insect.
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Affiliation(s)
- Jizhen Wei
- State Key Laboratory of Wheat and Maize Crop Science, College of Plant Protection, Henan Agricultural University, Zhengzhou, China
| | - Yaling Zhang
- State Key Laboratory of Wheat and Maize Crop Science, College of Plant Protection, Henan Agricultural University, Zhengzhou, China
- Tibet Academy of Agriculture and Animal Husbandry Sciences, Lhasa, China
| | - Shiheng An
- State Key Laboratory of Wheat and Maize Crop Science, College of Plant Protection, Henan Agricultural University, Zhengzhou, China
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Yang X, Chen W, Song X, Ma X, Cotto-Rivera RO, Kain W, Chu H, Chen YR, Fei Z, Wang P. Mutation of ABC transporter ABCA2 confers resistance to Bt toxin Cry2Ab in Trichoplusia ni. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2019; 112:103209. [PMID: 31422154 DOI: 10.1016/j.ibmb.2019.103209] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Revised: 07/22/2019] [Accepted: 07/24/2019] [Indexed: 05/29/2023]
Abstract
Insecticidal proteins from Bacillus thuringiensis (Bt) are the primary recombinant proteins expressed in transgenic crops (Bt-crops) to confer insect resistance. Development of resistance to Bt toxins in insect populations threatens the sustainable application of Bt-crops in agriculture. The Bt toxin Cry2Ab is a major insecticidal protein used in current Bt-crops, and resistance to Cry2Ab has been selected in several insects, including the cabbage looper, Trichoplusia ni. In this study, the Cry2Ab resistance gene in T. ni was mapped to Chromosome 17 by genetic linkage analyses using a whole genome resequencing approach, and was then finely mapped using RNA-seq-based bulked segregant analysis (BSA) and amplicon sequencing (AmpSeq)-based fine linkage mapping to a locus containing two genes, ABCA1 and ABCA2. Mutations in ABCA1 and ABCA2 in Cry2Ab resistant T. ni were identified by both genomic DNA and cDNA sequencing. Analysis of the expression of ABCA1 and ABCA2 in T. ni larvae indicated that ABCA2 is abundantly expressed in the larval midgut, but ABCA1 is not a midgut-expressed gene. The mutation in ABCA2 in Cry2Ab resistant T. ni was identified to be an insertion of a transposon Tntransib in ABCA2. For confirmation of ABCA2 as the Cry2Ab-resistance gene, T. ni mutants with frameshift mutations in ABCA1 and ABCA2 were generated by CRISPR/Cas9 mutagenesis. Bioassays of the T. ni mutants with Cry2Ab verified that the mutations of ABCA1 did not change larval susceptibility to Cry2Ab, but the ABCA2 mutants were highly resistant to Cry2Ab. Genetic complementation test of the ABCA2 allele in Cry2Ab resistant T. ni with an ABCA2 mutant generated by CRISPR/Cas9 confirmed that the ABCA2 mutation in the Cry2Ab resistant strain confers the resistance. The results from this study confirmed that ABCA2 is essential for the toxicity of Cry2Ab in T. ni and mutation of ABCA2 confers the resistance to Cry2Ab in the resistant T. ni strain derived from a Bt resistant greenhouse population.
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Affiliation(s)
- Xiaowei Yang
- Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY, 14456, USA
| | - Wenbo Chen
- Boyce Thompson Institute, Ithaca, NY, 14853, USA
| | - Xiaozhao Song
- Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY, 14456, USA
| | - Xiaoli Ma
- Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY, 14456, USA
| | - Rey O Cotto-Rivera
- Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY, 14456, USA
| | - Wendy Kain
- Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY, 14456, USA
| | - Hannah Chu
- Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY, 14456, USA; Department of Science, John Jay College of Criminal Justice-City University of New York, New York, NY, 10019, USA
| | - Yun-Ru Chen
- Boyce Thompson Institute, Ithaca, NY, 14853, USA
| | - Zhangjun Fei
- Boyce Thompson Institute, Ithaca, NY, 14853, USA; USDA-Agricultural Research Service, Robert W. Holley Center for Agriculture and Health, Ithaca, NY, 14853, USA
| | - Ping Wang
- Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY, 14456, USA.
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11
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Guo W, Kain W, Wang P. Effects of disruption of the peritrophic membrane on larval susceptibility to Bt toxin Cry1Ac in cabbage loopers. JOURNAL OF INSECT PHYSIOLOGY 2019; 117:103897. [PMID: 31199901 DOI: 10.1016/j.jinsphys.2019.103897] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Revised: 06/05/2019] [Accepted: 06/10/2019] [Indexed: 06/09/2023]
Abstract
The insect midgut peritrophic membrane (or peritrophic matrix) (PM) is an extracellular structure, lining the midgut epithelium. The PM facilitates the food digestion process and plays important roles in insect-microbe interactions as a barrier against microbial pathogens. The soil bacterium, Bacillus thuringiensis (Bt), and its proteinaceous toxins are widely used for insect control. To understand the protective role of PM in insects against Bt toxins, the effect of PM on larval susceptibility to Bt toxin Cry1Ac was examined in Cry1Ac-susceptible and -resistant strains of the cabbage looper, Trichoplusia ni. The PM in T. ni was disrupted, using a baculovirus enhancin (TnGV enhancin) to degrade the major PM mucin protein IIM and a chitin binding chemical, Calcofluor, to inhibit the binding of PM proteins to chitin. Bioassays of the susceptibility of T. ni larvae to Cry1Ac with treatment of TnGV enhancin showed significantly increased larval mortality in both the Cry1Ac susceptible and resistant strains, confirming that the PM is a protective barrier to the passage of Cry1Ac and plays a protective role against the toxin. However, treatment of T. ni larvae with Calcofluor significantly reduced the larval susceptibility to Cry1Ac. The level of mortality reduction by treatment with Calcofluor was more significant in the resistant T. ni strains than in the susceptible strain. The mechanism for the decrease of susceptibility to Cry1Ac in T. ni treated with Calcofluor needs to be understood. It may result from binding of the toxin to the over expressed PM proteins, preventing the Cry1Ac from reaching the midgut receptor for the toxin or from potential binding of Calcofluor to the midgut receptor for Cry1Ac, leading to inhibition of the toxicity of Cry1Ac in larvae.
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Affiliation(s)
- Wei Guo
- Department of Entomology, Cornell University, Geneva, NY 14456, USA
| | - Wendy Kain
- Department of Entomology, Cornell University, Geneva, NY 14456, USA
| | - Ping Wang
- Department of Entomology, Cornell University, Geneva, NY 14456, USA.
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Wei J, Zhang M, Liang G, Li X. Alkaline phosphatase 2 is a functional receptor of Cry1Ac but not Cry2Ab in Helicoverpa zea. INSECT MOLECULAR BIOLOGY 2019; 28:372-379. [PMID: 30474197 DOI: 10.1111/imb.12556] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Although membrane-bound alkaline phosphatases (ALPs) have been proposed as a receptor for Cry1Ac in a few lepidopteran species, their potential functions as a Cry2Ab receptor are yet to be verified. To determine if ALP2 also serves as a receptor for Cry1Ac and even for Cry2Ab in Helicoverpa zea, we measured the potency of activated Cry1Ac and Cry2Ab against midgut and fat body cell lines of H. zea and the ovarian cell line of Spodoptera frugiperda (Sf9) expressing H. zea ALP2 (HzALP2) or transfected with HzALP2 double-stranded RNA (dsRNA). Relative to the control cells, the three cell lines expressing HzALP2 were more susceptible to Cry1Ac but there was no difference for Cry2Ab. By contrast, the two H. zea cell lines transfected with HzALP2 dsRNA were resistant to Cry1Ac while kept susceptible to Cry2Ab. Furthermore, RNA interference knockdown of HzALP2 in H. zea larvae enhanced larval survival on Cry1Ac-containing diets. These findings indicate that HzALP2 functions as a receptor of Cry1Ac but not Cry2Ab.
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Affiliation(s)
- J Wei
- State Key Laboratory of Wheat and Maize Crop Science/College of Plant Protection, Henan Agricultural University, Zhengzhou, China
- Department of Entomology and BIO5 Institute, University of Arizona, Tucson, AZ, USA
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
| | - M Zhang
- Department of Entomology and BIO5 Institute, University of Arizona, Tucson, AZ, USA
- School of Agricultural Sciencies, Zhengzhou University, Zhengzhou, Henan, China
| | - G Liang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
| | - X Li
- Department of Entomology and BIO5 Institute, University of Arizona, Tucson, AZ, USA
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13
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Ma XL, He WY, Wang P, You MS. Cell lines from diamondback moth exhibiting differential susceptibility to baculovirus infection and expressing midgut genes. INSECT SCIENCE 2019; 26:251-262. [PMID: 28857510 DOI: 10.1111/1744-7917.12533] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2017] [Revised: 07/21/2017] [Accepted: 08/03/2017] [Indexed: 06/07/2023]
Abstract
Six new cell lines were established from embryonic tissues of the diamondback moth, Plutella xylostella (L.). The cell lines showed differential characteristics, including growth in attachment or in suspension, susceptibility to a baculovirus infection and expression of genes involved in the glucosinolate detoxification pathway in P. xylostella larvae. Five of the cell lines grew attached to the culture flask and one cell line grew unattached as a suspension cell line. The cell lines had population doubling times ranging from 18 to 23 h. Among five of the P. xylostella cell lines examined for infection of a nucleopolyhedrovirus from Autographa californica, AcMNPV, four cell lines were highly susceptible to AcMNPV infection, but one was only semi-permissive to AcMNPV infection. The production of two recombinant proteins, a β-galactosidase of bacterial origin and a secreted alkaline phosphatase of eukaryotic origin, in the P. xylostella cell lines was examined in comparison with that in the cell line Sf9 which is commonly used for recombinant protein production. In the P. xylostella cell lines, expression of three important midgut genes involved in the glucosinolate detoxification pathway, including the glucosinolate sulfatase genes GSS1 and GSS2 and the sulfatase modifying factor gene SUMF1, was detected. The P. xylostella cell lines developed in this study could be useful in in vitro research systems for studying insec-virus interactions and complex molecular mechanisms in glucosinolate detoxification and insect-plant interactions.
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Affiliation(s)
- Xiao-Li Ma
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Fujian Agriculture and Forestry University, Fuzhou, China
- Fujian-Taiwan Joint Centre for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, Fuzhou, China
- Key Laboratory of Integrated Pest Management for Fujian-Taiwan Crops, Ministry of Agriculture, Fujian Agriculture and Forestry University, Fuzhou, China
- Institute of Applied Ecology, Fujian Agriculture and Forestry University, Fuzhou, China
- Department of Entomology, Cornell University, Geneva, NY, USA
| | - Wei-Yi He
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Fujian Agriculture and Forestry University, Fuzhou, China
- Fujian-Taiwan Joint Centre for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, Fuzhou, China
- Key Laboratory of Integrated Pest Management for Fujian-Taiwan Crops, Ministry of Agriculture, Fujian Agriculture and Forestry University, Fuzhou, China
- Institute of Applied Ecology, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Ping Wang
- Department of Entomology, Cornell University, Geneva, NY, USA
| | - Min-Sheng You
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Fujian Agriculture and Forestry University, Fuzhou, China
- Fujian-Taiwan Joint Centre for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, Fuzhou, China
- Key Laboratory of Integrated Pest Management for Fujian-Taiwan Crops, Ministry of Agriculture, Fujian Agriculture and Forestry University, Fuzhou, China
- Institute of Applied Ecology, Fujian Agriculture and Forestry University, Fuzhou, China
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14
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Chen W, Yang X, Tetreau G, Song X, Coutu C, Hegedus D, Blissard G, Fei Z, Wang P. A high‐quality chromosome‐level genome assembly of a generalist herbivore,
Trichoplusia ni. Mol Ecol Resour 2019; 19:485-496. [DOI: 10.1111/1755-0998.12966] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 11/07/2018] [Accepted: 11/12/2018] [Indexed: 01/01/2023]
Affiliation(s)
- Wenbo Chen
- Boyce Thompson Institute Ithaca New York
| | - Xiaowei Yang
- Department of Entomology Cornell University, New York State Agricultural Experiment Station Geneva New York
| | - Guillaume Tetreau
- Department of Entomology Cornell University, New York State Agricultural Experiment Station Geneva New York
| | - Xiaozhao Song
- Department of Entomology Cornell University, New York State Agricultural Experiment Station Geneva New York
| | - Cathy Coutu
- Saskatoon Research and Development Centre, Agriculture and Agri‐Food Canada Saskatoon Saskatchewan Canada
| | - Dwayne Hegedus
- Saskatoon Research and Development Centre, Agriculture and Agri‐Food Canada Saskatoon Saskatchewan Canada
| | | | - Zhangjun Fei
- Boyce Thompson Institute Ithaca New York
- USDA‐Agricultural Research Service, Robert W. Holley Center for Agriculture and Health Ithaca New York
| | - Ping Wang
- Department of Entomology Cornell University, New York State Agricultural Experiment Station Geneva New York
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15
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Sohrab SS. Development of Virus Resistance Transgenic Cotton Using Cotton Leaf Curl Virus Antisense ßC1 Gene. Methods Mol Biol 2019; 1902:293-305. [PMID: 30543080 DOI: 10.1007/978-1-4939-8952-2_24] [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] [Indexed: 06/09/2023]
Abstract
Cotton (Gossypium hirsutum L.) is the most economically important crop in the world and produced 90% of the total natural cellulose fiber which is utilized to make cotton fabrics. The production of cotton is affected by many several diseases, and among them, viral disease, especially leaf curl, is the most destructive disease caused by a begomovirus transmitted by whiteflies vector. Plant biotechnology has provided an opportunity to develop transgenic plant with variable traits against biotic and abiotic stress such as resistance against pathogens, yield, quality, and salinity. Transgenic cotton (Gossypium hirsutum L., cv. Coker 312) plants were raised against leaf curl disease using bC1 gene in antisense orientation through Agrobacterium-mediated transformation somatic embryogenesis system. In this chapter, a standardized protocol will be given to raise virus resistance transgenic cotton.
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Affiliation(s)
- S S Sohrab
- Special Infectious Agents Unit, King Fahd Medical Research Center, King Abdulaziz University, Jeddah, Kingdom of Saudi Arabia.
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16
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Bacillus thuringiensis-Based Gene Pyramiding: a Way Forward for a Combined Horizontal and Vertical Resistance in Plant. BACILLI IN CLIMATE RESILIENT AGRICULTURE AND BIOPROSPECTING 2019. [DOI: 10.1007/978-3-030-15175-1_15] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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17
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ABC transporter mis-splicing associated with resistance to Bt toxin Cry2Ab in laboratory- and field-selected pink bollworm. Sci Rep 2018; 8:13531. [PMID: 30202031 PMCID: PMC6131251 DOI: 10.1038/s41598-018-31840-5] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Accepted: 08/28/2018] [Indexed: 11/13/2022] Open
Abstract
Evolution of pest resistance threatens the benefits of genetically engineered crops that produce Bacillus thuringiensis (Bt) insecticidal proteins. Strategies intended to delay pest resistance are most effective when implemented proactively. Accordingly, researchers have selected for and analyzed resistance to Bt toxins in many laboratory strains of pests before resistance evolves in the field, but the utility of this approach depends on the largely untested assumption that laboratory- and field-selected resistance to Bt toxins are similar. Here we compared the genetic basis of resistance to Bt toxin Cry2Ab, which is widely deployed in transgenic crops, between laboratory- and field-selected populations of the pink bollworm (Pectinophora gossypiella), a global pest of cotton. We discovered that resistance to Cry2Ab is associated with mutations disrupting the same ATP-binding cassette transporter gene (PgABCA2) in a laboratory-selected strain from Arizona, USA, and in field-selected populations from India. The most common mutation, loss of exon 6 caused by alternative splicing, occurred in resistant larvae from both locations. Together with previous data, the results imply that mutations in the same gene confer Bt resistance in laboratory- and field-selected strains and suggest that focusing on ABCA2 genes may help to accelerate progress in monitoring and managing resistance to Cry2Ab.
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18
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Analysis of cross-resistance to Vip3 proteins in eight insect colonies, from four insect species, selected for resistance to Bacillus thuringiensis insecticidal proteins. J Invertebr Pathol 2018; 155:64-70. [DOI: 10.1016/j.jip.2018.05.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Revised: 05/10/2018] [Accepted: 05/14/2018] [Indexed: 11/20/2022]
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19
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Onofre J, Gaytán MO, Peña-Cardeña A, García-Gomez BI, Pacheco S, Gómez I, Bravo A, Soberón M. Identification of Aminopeptidase-N2 as a Cry2Ab binding protein in Manduca sexta. Peptides 2017; 98:93-98. [PMID: 28108197 DOI: 10.1016/j.peptides.2017.01.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Revised: 01/06/2017] [Accepted: 01/09/2017] [Indexed: 11/15/2022]
Abstract
Bacillus thuringiensis Cry2Ab toxin has been used in combination with Cry1Ac for resistance management on the Bt-cotton that is widely planted worldwide. However, little is known regarding Cry2Ab mode of action. Particularly, there is a gap of knowledge on the identification of insect midgut proteins that bind Cry2Ab and mediate toxicity. In the case of Cry1Ab toxin, a transmembrane cadherin protein and glycosyl-phosphatidylinositol (GPI) anchored proteins like aminopeptidase-N1 (APN1) or alkaline-phosphatase (ALP) from Manduca sexta, have been shown to be important for oligomer formation and insertion into the membrane. Binding competition experiments showed that Cry2Ab toxin does not share binding sites with Cry1Ab toxin in M. sexta brush border membrane vesicles (BBMV). Also, that Cry2Ab shows reduced binding to the Cry1Ab binding molecules cadherin, APN1 or ALP. Finally, ligand blot experiments and protein sequence by LC-MS/MS identified APN2 isoform as a Cry2Ab binding protein. Cloning and expression of APN2 confirmed that APN2 is a Cry2Ab binding protein.
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Affiliation(s)
- Janette Onofre
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo, Postal 510-3, Cuernavaca 62250, Morelos, Mexico
| | - Meztlli O Gaytán
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo, Postal 510-3, Cuernavaca 62250, Morelos, Mexico
| | - Arlen Peña-Cardeña
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo, Postal 510-3, Cuernavaca 62250, Morelos, Mexico
| | - Blanca I García-Gomez
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo, Postal 510-3, Cuernavaca 62250, Morelos, Mexico
| | - Sabino Pacheco
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo, Postal 510-3, Cuernavaca 62250, Morelos, Mexico
| | - Isabel Gómez
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo, Postal 510-3, Cuernavaca 62250, Morelos, Mexico
| | - Alejandra Bravo
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo, Postal 510-3, Cuernavaca 62250, Morelos, Mexico
| | - Mario Soberón
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo, Postal 510-3, Cuernavaca 62250, Morelos, Mexico.
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20
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Tetreau G, Wang R, Wang P. Fitness of Bt-resistant cabbage loopers on Bt cotton plants. PLANT BIOTECHNOLOGY JOURNAL 2017; 15:1322-1330. [PMID: 28273400 PMCID: PMC5595710 DOI: 10.1111/pbi.12718] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Revised: 02/22/2017] [Accepted: 03/01/2017] [Indexed: 06/01/2023]
Abstract
Development of resistance to the insecticidal toxins from Bacillus thuringiensis (Bt) in insects is the major threat to the continued success of transgenic Bt crops in agriculture. The fitness of Bt-resistant insects on Bt and non-Bt plants is a key parameter that determines the development of Bt resistance in insect populations. In this study, a comprehensive analysis of the fitness of Bt-resistant Trichoplusia ni strains on Bt cotton leaves was conducted. The Bt-resistant T. ni strains carried two genetically independent mechanisms of resistance to Bt toxins Cry1Ac and Cry2Ab. The effects of the two resistance mechanisms, individually and in combination, on the fitness of the T. ni strains on conventional non-Bt cotton and on transgenic Bt cotton leaves expressing a single-toxin Cry1Ac (Bollgard I) or two Bt toxins Cry1Ac and Cry2Ab (Bollgard II) were examined. The presence of Bt toxins in plants reduced the fitness of resistant insects, indicated by decreased net reproductive rate (R0 ) and intrinsic rate of increase (r). The reduction in fitness in resistant T. ni on Bollgard II leaves was greater than that on Bollgard I leaves. A 12.4-day asynchrony of adult emergence between the susceptible T. ni grown on non-Bt cotton leaves and the dual-toxin-resistant T. ni on Bollgard II leaves was observed. Therefore, multitoxin Bt plants not only reduce the probability for T. ni to develop resistance but also strongly reduce the fitness of resistant insects feeding on the plants.
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Affiliation(s)
- Guillaume Tetreau
- Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY, USA
| | - Ran Wang
- Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY, USA
- Department of Entomology, Nanjing Agricultural University, Nanjing, China
| | - Ping Wang
- Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY, USA
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21
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Peralta C, Palma L. Is the Insect World Overcoming the Efficacy of Bacillus thuringiensis? Toxins (Basel) 2017; 9:toxins9010039. [PMID: 28106770 PMCID: PMC5308271 DOI: 10.3390/toxins9010039] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Revised: 01/05/2017] [Accepted: 01/10/2017] [Indexed: 12/20/2022] Open
Abstract
The use of chemical pesticides revolutionized agriculture with the introduction of DDT (Dichlorodiphenyltrichloroethane) as the first modern chemical insecticide. However, the effectiveness of DDT and other synthetic pesticides, together with their low cost and ease of use, have led to the generation of undesirable side effects, such as pollution of water and food sources, harm to non-target organisms and the generation of insect resistance. The alternative comes from biological control agents, which have taken an expanding share in the pesticide market over the last decades mainly promoted by the necessity to move towards more sustainable agriculture. Among such biological control agents, the bacterium Bacillus thuringiensis (Bt) and its insecticidal toxins have been the most studied and commercially used biological control agents over the last 40 years. However, some insect pests have acquired field-evolved resistance to the most commonly used Bt-based pesticides, threatening their efficacy, which necessitates the immediate search for novel strains and toxins exhibiting different modes of action and specificities in order to perpetuate the insecticidal potential of this bacterium.
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Affiliation(s)
- Cecilia Peralta
- Centro de Investigaciones y Transferencia de Villa María (CITVM-CONICET), Universidad Nacional de Villa María, 5900 Villa María, Córdoba, Argentina.
- Consejo Nacional de Investigaciones Científicas y Técnicas, C1 425FQB Ciudad Autónoma de Buenos Aires, Argentina.
| | - Leopoldo Palma
- Centro de Investigaciones y Transferencia de Villa María (CITVM-CONICET), Universidad Nacional de Villa María, 5900 Villa María, Córdoba, Argentina.
- Consejo Nacional de Investigaciones Científicas y Técnicas, C1 425FQB Ciudad Autónoma de Buenos Aires, Argentina.
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22
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Continuous evolution of Bacillus thuringiensis toxins overcomes insect resistance. Nature 2016; 533:58-63. [PMID: 27120167 PMCID: PMC4865400 DOI: 10.1038/nature17938] [Citation(s) in RCA: 138] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2015] [Accepted: 03/23/2016] [Indexed: 12/17/2022]
Abstract
The Bacillus thuringiensis δ-endotoxins (Bt toxins) are widely used insecticidal proteins in engineered crops that provide agricultural, economic, and environmental benefits. The development of insect resistance to Bt toxins endangers their long-term effectiveness. Here we have developed a phage-assisted continuous evolution selection that rapidly evolves high-affinity protein-protein interactions, and applied this system to evolve variants of the Bt toxin Cry1Ac that bind a cadherin-like receptor from the insect pest Trichoplusia ni (TnCAD) that is not natively bound by wild-type Cry1Ac. The resulting evolved Cry1Ac variants bind TnCAD with high affinity (dissociation constant Kd = 11-41 nM), kill TnCAD-expressing insect cells that are not susceptible to wild-type Cry1Ac, and kill Cry1Ac-resistant T. ni insects up to 335-fold more potently than wild-type Cry1Ac. Our findings establish that the evolution of Bt toxins with novel insect cell receptor affinity can overcome insect Bt toxin resistance and confer lethality approaching that of the wild-type Bt toxin against non-resistant insects.
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23
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Wang R, Tetreau G, Wang P. Effect of crop plants on fitness costs associated with resistance to Bacillus thuringiensis toxins Cry1Ac and Cry2Ab in cabbage loopers. Sci Rep 2016; 6:20959. [PMID: 26868936 PMCID: PMC4751490 DOI: 10.1038/srep20959] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Accepted: 01/13/2016] [Indexed: 01/01/2023] Open
Abstract
Fitness costs associated with resistance to Bacillus thuringiensis (Bt) toxins critically impact the development of resistance in insect populations. In this study, the fitness costs in Trichoplusia ni strains associated with two genetically independent resistance mechanisms to Bt toxins Cry1Ac and Cry2Ab, individually and in combination, on four crop plants (cabbage, cotton, tobacco and tomato) were analyzed, in comparison with their near-isogenic susceptible strain. The net reproductive rate (R0) and intrinsic rate of increase (r) of the T. ni strains, regardless of their resistance traits, were strongly affected by the host plants. The ABCC2 gene-linked mechanism of Cry1Ac resistance was associated with relatively low fitness costs, while the Cry2Ab resistance mechanism was associated with higher fitness costs. The fitness costs in the presence of both resistance mechanisms in T. ni appeared to be non-additive. The relative fitness of Bt-resistant T. ni depended on the specific resistance mechanisms as well as host plants. In addition to difference in survivorship and fecundity, an asynchrony of adult emergence was observed among T. ni with different resistance mechanisms and on different host plants. Therefore, mechanisms of resistance and host plants available in the field are both important factors affecting development of Bt resistance in insects.
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Affiliation(s)
- Ran Wang
- Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY 14456, USA.,Department of Entomology, Nanjing Agricultural University, Nanjing 210095, China
| | - Guillaume Tetreau
- Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY 14456, USA
| | - Ping Wang
- Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY 14456, USA
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APN1 is a functional receptor of Cry1Ac but not Cry2Ab in Helicoverpa zea. Sci Rep 2016; 6:19179. [PMID: 26755166 PMCID: PMC4709634 DOI: 10.1038/srep19179] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2015] [Accepted: 12/04/2015] [Indexed: 01/03/2023] Open
Abstract
Lepidopteran midgut aminopeptidases N (APNs) are phylogenetically divided into eight clusters, designated as APN1-8. Although APN1 has been implicated as one of the receptors for Cry1Ac in several species, its potential role in the mode of action of Cry2Ab has not been functionally determined so far. To test whether APN1 also acts as one of the receptors for Cry1Ac in Helicoverpa zea and even for Cry2Ab in this species, we conducted a gain of function analysis by heterologously expressing H. zea APN1 (HzAPN1) in the midgut and fat body cell lines of H. zea and the ovarian cell line of Spodoptera frugiperda (Sf9) and a loss of function analysis by RNAi (RNA interference) silencing of the endogenous APN1 in the three cell lines using the HzAPN1 double strand RNA (dsRNA). Heterologous expression of HzAPN1 significantly increased the susceptibility of the three cell lines to Cry1Ac, but had no effects on their susceptibility to Cry2Ab. Knocking down of the endogenous APN1 made the three cell lines resistant to Cry1Ac, but didn't change cell lines susceptibility to Cry2Ab. The findings from this study demonstrate that HzAPN1 is a functional receptor of Cry1Ac, but not Cry2Ab.
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25
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Tay WT, Mahon RJ, Heckel DG, Walsh TK, Downes S, James WJ, Lee SF, Reineke A, Williams AK, Gordon KHJ. Insect Resistance to Bacillus thuringiensis Toxin Cry2Ab Is Conferred by Mutations in an ABC Transporter Subfamily A Protein. PLoS Genet 2015; 11:e1005534. [PMID: 26583651 PMCID: PMC4652872 DOI: 10.1371/journal.pgen.1005534] [Citation(s) in RCA: 122] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Accepted: 08/25/2015] [Indexed: 12/15/2022] Open
Abstract
The use of conventional chemical insecticides and bacterial toxins to control lepidopteran pests of global agriculture has imposed significant selection pressure leading to the rapid evolution of insecticide resistance. Transgenic crops (e.g., cotton) expressing the Bt Cry toxins are now used world wide to control these pests, including the highly polyphagous and invasive cotton bollworm Helicoverpa armigera. Since 2004, the Cry2Ab toxin has become widely used for controlling H. armigera, often used in combination with Cry1Ac to delay resistance evolution. Isolation of H. armigera and H. punctigera individuals heterozygous for Cry2Ab resistance in 2002 and 2004, respectively, allowed aspects of Cry2Ab resistance (level, fitness costs, genetic dominance, complementation tests) to be characterised in both species. However, the gene identity and genetic changes conferring this resistance were unknown, as was the detailed Cry2Ab mode of action. No cross-resistance to Cry1Ac was observed in mutant lines. Biphasic linkage analysis of a Cry2Ab-resistant H. armigera family followed by exon-primed intron-crossing (EPIC) marker mapping and candidate gene sequencing identified three independent resistance-associated INDEL mutations in an ATP-Binding Cassette (ABC) transporter gene we named HaABCA2. A deletion mutation was also identified in the H. punctigera homolog from the resistant line. All mutations truncate the ABCA2 protein. Isolation of further Cry2Ab resistance alleles in the same gene from field H. armigera populations indicates unequal resistance allele frequencies and the potential for Bt resistance evolution. Identification of the gene involved in resistance as an ABC transporter of the A subfamily adds to the body of evidence on the crucial role this gene family plays in the mode of action of the Bt Cry toxins. The structural differences between the ABCA2, and that of the C subfamily required for Cry1Ac toxicity, indicate differences in the detailed mode-of-action of the two Bt Cry toxins. Transgenic crops expressing the insecticidal protein Cry2Ab from Bacillus thuringiensis (Bt) are used worldwide to suppress damage by lepidopteran pests, often used in combination with Cry1Ac toxin to delay resistance evolution. Until now, the Cry2Ab mode of action and the mechanism of resistance were unknown, with field-isolated Cry2Ab resistant Helicoverpa armigera showing no cross-resistance to Cry1Ac. In this study, biphasic linkage analysis of a Cry2Ab-resistant H. armigera family followed by EPIC marker mapping and candidate gene sequencing identified three independent INDEL mutations in an ATP-Binding Cassette transporter subfamily A gene (ABCA2). A deletion mutation was identified in the same gene of resistant H. punctigera. All four mutations are predicted to truncate the ABCA2 protein. This is the first molecular genetic characterization of insect resistance to the Cry2Ab toxin, and detection of diverse Cry2Ab resistance alleles will contribute to understanding the micro-evolutionary processes that underpinned lepidopteran Bt-resistance.
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Affiliation(s)
- Wee Tek Tay
- CSIRO, Black Mountain Laboratories, Canberra, Australian Capital Territory, Australia
- * E-mail:
| | - Rod J. Mahon
- CSIRO, Black Mountain Laboratories, Canberra, Australian Capital Territory, Australia
| | - David G. Heckel
- Department of Entomology, Max-Planck Institute for Chemical Ecology, Beutenberg Campus, Jena, Germany
| | - Thomas K. Walsh
- CSIRO, Black Mountain Laboratories, Canberra, Australian Capital Territory, Australia
| | - Sharon Downes
- CSIRO, Australian Cotton Research Institute, Narrabri, New South Wales, Australia
| | - William J. James
- CSIRO, Black Mountain Laboratories, Canberra, Australian Capital Territory, Australia
| | - Sui-Fai Lee
- Department of Genetics, University of Melbourne, Parkville, Victoria, Australia
| | - Annette Reineke
- Institute for Phytomedicine, Center of Applied Biology, Geisenheim University, Geiesenheim, Germany
| | - Adam K. Williams
- Department of Genetics, University of Melbourne, Parkville, Victoria, Australia
| | - Karl H. J. Gordon
- CSIRO, Black Mountain Laboratories, Canberra, Australian Capital Territory, Australia
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Fabrick JA, Unnithan GC, Yelich AJ, DeGain B, Masson L, Zhang J, Carrière Y, Tabashnik BE. Multi-Toxin Resistance Enables Pink Bollworm Survival on Pyramided Bt Cotton. Sci Rep 2015; 5:16554. [PMID: 26559899 PMCID: PMC5156061 DOI: 10.1038/srep16554] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Accepted: 10/15/2015] [Indexed: 11/09/2022] Open
Abstract
Transgenic crops producing Bacillus thuringiensis (Bt) proteins kill key insect pests, providing economic and environmental benefits. However, the evolution of pest resistance threatens the continued success of such Bt crops. To delay or counter resistance, transgenic plant "pyramids" producing two or more Bt proteins that kill the same pest have been adopted extensively. Field populations of the pink bollworm (Pectinophora gossypiella) in the United States have remained susceptible to Bt toxins Cry1Ac and Cry2Ab, but field-evolved practical resistance to Bt cotton producing Cry1Ac has occurred widely in India. Here we used two rounds of laboratory selection to achieve 18,000- to 150,000-fold resistance to Cry2Ab in pink bollworm. Inheritance of resistance to Cry2Ab was recessive, autosomal, conferred primarily by one locus, and independent of Cry1Ac resistance. We created a strain with high resistance to both toxins by crossing the Cry2Ab-resistant strain with a Cry1Ac-resistant strain, followed by one selection with Cry2Ab. This multi-toxin resistant strain survived on field-collected Bt cotton bolls producing both toxins. The results here demonstrate the risk of evolution of resistance to pyramided Bt plants, particularly when toxins are deployed sequentially and refuges are scarce, as seen with Bt cotton and pink bollworm in India.
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Affiliation(s)
- Jeffrey A Fabrick
- USDA ARS, U.S. Arid Land Agricultural Research Center, Maricopa, AZ 85138 USA
| | | | - Alex J Yelich
- Department of Entomology, University of Arizona, Tucson, AZ 85721 USA
| | - Ben DeGain
- Department of Entomology, University of Arizona, Tucson, AZ 85721 USA
| | - Luke Masson
- Biotechnology Research Institute, National Research Council of Canada, Montreal, QC, Canada H4P 2R2
| | - Jie Zhang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, Haidian District, 100193 Peoples Republic of China
| | - Yves Carrière
- Department of Entomology, University of Arizona, Tucson, AZ 85721 USA
| | - Bruce E Tabashnik
- Department of Entomology, University of Arizona, Tucson, AZ 85721 USA
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