1
|
Afzal MBS, Ijaz M, Abbas N, Shad SA, Serrão JE. Resistance of Lepidopteran Pests to Bacillus thuringiensis Toxins: Evidence of Field and Laboratory Evolved Resistance and Cross-Resistance, Mode of Resistance Inheritance, Fitness Costs, Mechanisms Involved and Management Options. Toxins (Basel) 2024; 16:315. [PMID: 39057955 PMCID: PMC11281168 DOI: 10.3390/toxins16070315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2024] [Revised: 07/07/2024] [Accepted: 07/09/2024] [Indexed: 07/28/2024] Open
Abstract
Bacillus thuringiensis (Bt) toxins are potential alternatives to synthetic insecticides for the control of lepidopteran pests. However, the evolution of resistance in some insect pest populations is a threat and can reduce the effectiveness of Bt toxins. In this review, we summarize the results of 161 studies from 20 countries reporting field and laboratory-evolved resistance, cross-resistance, and inheritance, mechanisms, and fitness costs of resistance to different Bt toxins. The studies refer mainly to insects from the United States of America (70), followed by China (31), Brazil (19), India (12), Malaysia (9), Spain (3), and Australia (3). The majority of the studies revealed that most of the pest populations showed susceptibility and a lack of cross-resistance to Bt toxins. Factors that delay resistance include recessive inheritance of resistance, the low initial frequency of resistant alleles, increased fitness costs, abundant refuges of non-Bt, and pyramided Bt crops. The results of field and laboratory resistance, cross-resistance, and inheritance, mechanisms, and fitness cost of resistance are advantageous for predicting the threat of future resistance and making effective strategies to sustain the effectiveness of Bt crops.
Collapse
Affiliation(s)
- Muhammad Babar Shahzad Afzal
- Beekeeping & Hill Fruit Pests Research Station, Rawalpindi 46000, Pakistan;
- Department of Entomology, Faculty of Agricultural Sciences and Technology, Bahauddin Zakariya University, Multan 60800, Pakistan;
| | - Mamuna Ijaz
- Department of Entomology, Faculty of Agricultural Sciences and Technology, Bahauddin Zakariya University, Multan 60800, Pakistan;
| | - Naeem Abbas
- Pesticides and Environmental Toxicology Laboratory, Department of Plant Protection, College of Food and Agriculture Sciences, King Saud University, P.O. Box 2460, Riyadh 11451, Saudi Arabia
| | - Sarfraz Ali Shad
- Department of Entomology, Faculty of Agricultural Sciences and Technology, Bahauddin Zakariya University, Multan 60800, Pakistan;
| | - José Eduardo Serrão
- Department of General Biology, Federal University of Vicosa, Vicosa 36570-900, MG, Brazil;
| |
Collapse
|
2
|
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.
Collapse
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.
| |
Collapse
|
3
|
Wang S, Kain W, Wang P. Bacillus thuringiensis Cry1A toxins exert toxicity by multiple pathways in insects. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2018; 102:59-66. [PMID: 30278206 DOI: 10.1016/j.ibmb.2018.09.013] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Revised: 09/11/2018] [Accepted: 09/28/2018] [Indexed: 06/08/2023]
Abstract
Adoption of biotech crops engineered to express insecticidal toxins from Bacillus thuringiensis (Bt) has revolutionized insect pest control in agriculture. For continuing effective application and development of the environmentally friendly Bt biotechnology, it is fundamental to understand pathways of toxicity of Bt toxins in insects. In this study, mutations were introduced in the midgut cadherin gene in the cabbage looper, Trichoplusia ni, by CRISPR/Cas9 mutagenesis. T. ni strains with mutations in the genes of two major receptors for Bt toxins, the midgut cadherin and ABCC2, and three Cry1A toxins with shared and differential midgut binding sites were used as an experimental system to dissect the roles of the cadherin and ABCC2 in the pathways of toxicity of Bt toxins. Results from assays of responses of the T. ni strains to different Bt toxins revealed that the cadherin and ABCC2 play independent roles in the mode of action of Cry1A toxins and that Bt toxins exert insecticidal activity through multiple redundant pathways of toxicity in insects. Besides the cadherin and ABCC2 pathways, there exists an additional major pathway of toxicity to be identified for Cry1Aa. The results also confirmed that the toxicity of Cry2Ab involves neither the cadherin nor the ABCC2 protein. The multiple pathway model for Bt toxins clarified from this study provided new insights into the molecular modes of action of Bt toxins and mechanisms of insect resistance to Bt toxins.
Collapse
Affiliation(s)
- Shaohua Wang
- Department of Entomology, Cornell University, Geneva, NY, 14456, USA; School of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou, China
| | - Wendy Kain
- Department of Entomology, Cornell University, Geneva, NY, 14456, USA
| | - Ping Wang
- Department of Entomology, Cornell University, Geneva, NY, 14456, USA.
| |
Collapse
|
4
|
Wei J, Liang G, Wu K, Gu S, Guo Y, Ni X, Li X. Cytotoxicity and binding profiles of activated Cry1Ac and Cry2Ab to three insect cell lines. INSECT SCIENCE 2018; 25:655-666. [PMID: 28247982 DOI: 10.1111/1744-7917.12451] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2016] [Revised: 11/24/2016] [Accepted: 01/03/2017] [Indexed: 06/06/2023]
Abstract
While Cry1Ac has been known to bind with larval midgut proteins cadherin, APN (amino peptidase N), ALP (alkaline phosphatase) and ABCC2 (adenosine triphosphate-binding cassette transporter subfamily C2), little is known about the receptors of Cry2Ab. To provide a clue to the receptors of Cry2Ab, we tested the baseline cytotoxicity of activated Cry1Ac and Cry2Ab against the midgut and fat body cell lines of Helicoverpa zea and the ovary cell line of Spodoptera frugiperda (SF9). As expected, the descending order of cytotoxicity of Cry1Ac against the three cell lines in terms of 50% lethal concetration (LC50 ) was midgut (31.0 μg/mL) > fat body (59.0 μg/mL) and SF9 cell (99.6 μg/mL). By contrast, the fat body cell line (LC50 = 7.55 μg/mL) was about twice more susceptible to Cry2Ab than the midgut cell line (16.0 μg/mL), the susceptibility of which was not significantly greater than that of SF9 cells (27.0 μg/mL). Further, ligand blot showed the binding differences between Cry1Ac and Cry2Ab in the three cell lines. These results indicated that the receptors of Cry2Ab were enriched in fat body cells and thus largely different from the receptors of Cry1Ac, which were enriched in midgut cells.
Collapse
Affiliation(s)
- Jizhen Wei
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
- Department of Entomology and BIO5 Institute, University of Arizona, Tucson, AZ, USA
| | - Gemei Liang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Kongming Wu
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Shaohua Gu
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Yuyuan Guo
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Xinzhi Ni
- USDA-ARS, Crop Genetics and Breeding Research Unit, Tifton, GA, USA
| | - Xianchun Li
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
- Department of Entomology and BIO5 Institute, University of Arizona, Tucson, AZ, USA
| |
Collapse
|
5
|
Shao E, Lin L, Liu S, Zhang J, Chen X, Sha L, Huang Z, Huang B, Guan X. Analysis of Homologs of Cry-toxin Receptor-Related Proteins in the Midgut of a Non-Bt Target, Nilaparvata lugens (Stål) (Hemiptera: Delphacidae). JOURNAL OF INSECT SCIENCE (ONLINE) 2018; 18:4839024. [PMID: 29415259 PMCID: PMC5804751 DOI: 10.1093/jisesa/iex102] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Indexed: 05/13/2023]
Abstract
The brown planthopper (BPH) Nilaparvata lugens is one of the most destructive insect pests in the rice fields of Asia. Like other hemipteran insects, BPH is not susceptible to Cry toxins of Bacillus thuringiensis (Bt) or transgenic rice carrying Bt cry genes. Lack of Cry receptors in the midgut is one of the main reasons that BPH is not susceptible to the Cry toxins. The main Cry-binding proteins (CBPs) of the susceptible insects are cadherin, aminopeptidase N (APN), and alkaline phosphatase (ALP). In this study, we analyzed and validated de novo assembled transcripts from transcriptome sequencing data of BPH to identify and characterize homologs of cadherin, APN, and ALP. We then compared the cadherin-, APN-, and ALP-like proteins of BPH to previously reported CBPs to identify their homologs in BPH. The sequence analysis revealed that at least one cadherin, one APN, and two ALPs of BPH contained homologous functional domains identified from the Cry-binding cadherin, APN, and ALP, respectively. Quantitative real-time polymerase chain reaction used to verify the expression level of each putative Cry receptor homolog in the BPH midgut indicated that the CBPs homologous APN and ALP were expressed at high or medium-high levels while the cadherin was expressed at a low level. These results suggest that homologs of CBPs exist in the midgut of BPH. However, differences in key motifs of CBPs, which are functional in interacting with Cry toxins, may be responsible for insusceptibility of BPH to Cry toxins.
Collapse
Affiliation(s)
- Ensi Shao
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, School of Life Science, Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Key Lab of Biopesticides and Chemical Biology, MOE, Fujian Agriculture and Forestry University, Fuzhou, Fujian, PR China
- Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, 350002 Fuzhou, Fujian, PR China
- China National Engineering Research Center of JUNCAO Technology, Fujian Agriculture and Forestry University, 350002 Fuzhou, Fujian, PR China
| | - Li Lin
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, School of Life Science, Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Key Lab of Biopesticides and Chemical Biology, MOE, Fujian Agriculture and Forestry University, Fuzhou, Fujian, PR China
- Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, 350002 Fuzhou, Fujian, PR China
| | - Sijun Liu
- Department of Entomology, Iowa State University, Ames, IA, 50011
| | - Jiao Zhang
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, School of Life Science, Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Key Lab of Biopesticides and Chemical Biology, MOE, Fujian Agriculture and Forestry University, Fuzhou, Fujian, PR China
- Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, 350002 Fuzhou, Fujian, PR China
| | - Xuelin Chen
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, School of Life Science, Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Key Lab of Biopesticides and Chemical Biology, MOE, Fujian Agriculture and Forestry University, Fuzhou, Fujian, PR China
- Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, 350002 Fuzhou, Fujian, PR China
| | - Li Sha
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, School of Life Science, Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Key Lab of Biopesticides and Chemical Biology, MOE, Fujian Agriculture and Forestry University, Fuzhou, Fujian, PR China
- Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, 350002 Fuzhou, Fujian, PR China
| | - Zhipeng Huang
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, School of Life Science, Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Key Lab of Biopesticides and Chemical Biology, MOE, Fujian Agriculture and Forestry University, Fuzhou, Fujian, PR China
- Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, 350002 Fuzhou, Fujian, PR China
| | - Biwang Huang
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, School of Life Science, Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Key Lab of Biopesticides and Chemical Biology, MOE, Fujian Agriculture and Forestry University, Fuzhou, Fujian, PR China
- Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, 350002 Fuzhou, Fujian, PR China
| | - Xiong Guan
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, School of Life Science, Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Key Lab of Biopesticides and Chemical Biology, MOE, Fujian Agriculture and Forestry University, Fuzhou, Fujian, PR China
- Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, 350002 Fuzhou, Fujian, PR China
| |
Collapse
|
6
|
Park Y, Herrero S, Kim Y. A single type of cadherin is involved in Bacillus thuringiensis toxicity in Plutella xylostella. INSECT MOLECULAR BIOLOGY 2015; 24:624-633. [PMID: 26331576 DOI: 10.1111/imb.12188] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Cadherins have been described as one the main functional receptors for the toxins of the entomopathogenic bacterium, Bacillus thuringiensis (Bt). With the availability of the whole genome of Plutella xylostella, different types of cadherins have been annotated. In this study we focused on determining those members of the cadherin-related proteins that potentially play a role in the mode of action of Bt toxins. For this, we mined the genome of P. xylostella to identify these putative cadherins. The genome screening revealed 52 genes that were annotated as cadherin or cadherin-like genes. Further analysis revealed that six of these putative cadherins had three motifs common to all Bt-related cadherins: a signal peptide, cadherin repeats and a transmembrane domain. From the six selected cadherins, only P. xylostella cadherin 1 (PxCad1) was expressed in the larval midgut and only the silencing of this gene by RNA interference (double-stranded RNA feeding) reduce toxicity and binding to the midgut of the Cry1Ac type toxin from Bt. These results indicate that from the whole set of cadherin-related genes identified in P. xylostella, only PxCad1 is associated with the Cry1Ac mode of action.
Collapse
Affiliation(s)
- Y Park
- Department of Bioresource Sciences, Andong National University, Andong, Republic of Korea
| | - S Herrero
- Department of Genetics, Universitat de València, Burjassot, Spain
- Estructura de Recerca Interdisciplinar en Biotecnologia i Biomedicina (ERI BIOTECMED), Universitat de València, Burjassot, Spain
| | - Y Kim
- Department of Bioresource Sciences, Andong National University, Andong, Republic of Korea
| |
Collapse
|
7
|
Guo Z, Kang S, Zhu X, Wu Q, Wang S, Xie W, Zhang Y. The midgut cadherin-like gene is not associated with resistance to Bacillus thuringiensis toxin Cry1Ac in Plutella xylostella (L.). J Invertebr Pathol 2015; 126:21-30. [PMID: 25595643 DOI: 10.1016/j.jip.2015.01.004] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2014] [Revised: 12/24/2014] [Accepted: 01/07/2015] [Indexed: 11/16/2022]
Abstract
The Gram-positive bacterium Bacillus thuringiensis (Bt) produces Cry toxins that have been used to control important agricultural pests. Evolution of resistance in target pests threatens the effectiveness of these toxins when used either in sprayed biopesticides or in Bt transgenic crops. Although alterations of the midgut cadherin-like receptor can lead to Bt Cry toxin resistance in many insects, whether the cadherin gene is involved in Cry1Ac resistance of Plutella xylostella (L.) remains unclear. Here, we present experimental evidence that resistance to Cry1Ac or Bt var. kurstaki (Btk) in P. xylostella is not due to alterations of the cadherin gene. The bona fide P. xylostella cadherin cDNA sequence was cloned and analyzed, and comparisons of the cadherin cDNA sequence among susceptible and resistant P. xylostella strains confirmed that Cry1Ac resistance was independent of mutations in this gene. In addition, real-time quantitative PCR (qPCR) indicated that cadherin transcript levels did not significantly differ among susceptible and resistant P. xylostella strains. RNA interference (RNAi)-mediated suppression of cadherin gene expression did not affect larval susceptibility to Cry1Ac toxin. Furthermore, genetic linkage assays using four cadherin gDNA allelic biomarkers confirmed that the cadherin gene is not linked to resistance against Cry1Ac in P. xylostella. Taken together, our findings demonstrate that Cry1Ac resistance of P. xylostella is independent of the cadherin gene.
Collapse
Affiliation(s)
- Zhaojiang Guo
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
| | - Shi Kang
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
| | - Xun Zhu
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
| | - Qingjun Wu
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
| | - Shaoli Wang
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
| | - Wen Xie
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
| | - Youjun Zhang
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
| |
Collapse
|
8
|
Fabrick JA, Ponnuraj J, Singh A, Tanwar RK, Unnithan GC, Yelich AJ, Li X, Carrière Y, Tabashnik BE. Alternative splicing and highly variable cadherin transcripts associated with field-evolved resistance of pink bollworm to bt cotton in India. PLoS One 2014; 9:e97900. [PMID: 24840729 PMCID: PMC4026531 DOI: 10.1371/journal.pone.0097900] [Citation(s) in RCA: 107] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Accepted: 04/25/2014] [Indexed: 11/25/2022] Open
Abstract
Evolution of resistance by insect pests can reduce the benefits of insecticidal proteins from Bacillus thuringiensis (Bt) that are used extensively in sprays and transgenic crops. Despite considerable knowledge of the genes conferring insect resistance to Bt toxins in laboratory-selected strains and in field populations exposed to Bt sprays, understanding of the genetic basis of field-evolved resistance to Bt crops remains limited. In particular, previous work has not identified the genes conferring resistance in any cases where field-evolved resistance has reduced the efficacy of a Bt crop. Here we report that mutations in a gene encoding a cadherin protein that binds Bt toxin Cry1Ac are associated with field-evolved resistance of pink bollworm (Pectinophora gossypiella) in India to Cry1Ac produced by transgenic cotton. We conducted laboratory bioassays that confirmed previously reported resistance to Cry1Ac in pink bollworm from the state of Gujarat, where Bt cotton producing Cry1Ac has been grown extensively. Analysis of DNA from 436 pink bollworm from seven populations in India detected none of the four cadherin resistance alleles previously reported to be linked with resistance to Cry1Ac in laboratory-selected strains of pink bollworm from Arizona. However, DNA sequencing of pink bollworm derived from resistant and susceptible field populations in India revealed eight novel, severely disrupted cadherin alleles associated with resistance to Cry1Ac. For these eight alleles, analysis of complementary DNA (cDNA) revealed a total of 19 transcript isoforms, each containing a premature stop codon, a deletion of at least 99 base pairs, or both. Seven of the eight disrupted alleles each produced two or more different transcript isoforms, which implicates alternative splicing of messenger RNA (mRNA). This represents the first example of alternative splicing associated with field-evolved resistance that reduced the efficacy of a Bt crop.
Collapse
Affiliation(s)
- Jeffrey A. Fabrick
- U.S. Department of Agriculture, Agricultural Research Service, U.S. Arid Land Agricultural Research Center, Maricopa, Arizona, United States of America
- * E-mail:
| | - Jeyakumar Ponnuraj
- National Institute of Plant Health Management, Rajendranagar, Hyderabad, Andhra Pradesh, India
| | - Amar Singh
- National Centre for Integrated Pest Management, Indian Agricultural Research Institute, New Delhi, Delhi, India
| | - Raj K. Tanwar
- National Centre for Integrated Pest Management, Indian Agricultural Research Institute, New Delhi, Delhi, India
| | - Gopalan C. Unnithan
- Department of Entomology, University of Arizona, Tucson, Arizona, United States of America
| | - Alex J. Yelich
- Department of Entomology, University of Arizona, Tucson, Arizona, United States of America
| | - Xianchun Li
- Department of Entomology, University of Arizona, Tucson, Arizona, United States of America
| | - Yves Carrière
- Department of Entomology, University of Arizona, Tucson, Arizona, United States of America
| | - Bruce E. Tabashnik
- Department of Entomology, University of Arizona, Tucson, Arizona, United States of America
| |
Collapse
|
9
|
Hua G, Park Y, Adang MJ. Cadherin AdCad1 in Alphitobius diaperinus larvae is a receptor of Cry3Bb toxin from Bacillus thuringiensis. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2014; 45:11-17. [PMID: 24225445 DOI: 10.1016/j.ibmb.2013.10.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2013] [Revised: 10/17/2013] [Accepted: 10/22/2013] [Indexed: 06/02/2023]
Abstract
Bacillus thuringiensis (Bt) Cry proteins are used as components of biopesticides or expressed in transgenic crops to control diverse insect pests worldwide. These Cry toxins bind to receptors on the midgut brush border membrane and kill enterocytes culminating in larval mortality. Cadherin proteins have been identified as Cry toxin receptors in diverse lepidopteran, coleopteran, and dipteran species. In the present work we report a 185 kDa cadherin (AdCad1) from larvae of the lesser mealworm (Alphitobius diaperinus) larvae as the first identified receptor for Cry3Bb toxin. The AdCad1 protein contains typical structural components for Cry toxin receptor cadherins, including nine cadherin repeats (CR9), a membrane-proximal extracellular domain (MPED) and a cytosolic region. Peptides corresponding to the CR9 and MPED regions bound Cry3Bb toxin with high affinities (23 nM and 40 nM) and significantly synergized Cry3Bb toxicity against A. diperinus larvae. Silencing of AdCad1 expression through RNA interference resulted in highly reduced susceptibility to Cry3Bb in A. diperinus larvae. The CR9 peptide fed with toxin to RNAi-treated larvae restored Cry3Bb toxicity. These results are evidences that AdCad1 is a functional receptor of Cry3Bb toxin and that exogenously fed CR9 peptide can overcome the effect of reduced AdCad1expression on Cry3Bb toxicity to larvae.
Collapse
Affiliation(s)
- Gang Hua
- Department of Entomology, University of Georgia, Athens, GA 30602-2603, USA
| | - Youngjin Park
- 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.
| |
Collapse
|
10
|
RNA interference of cadherin gene expression in Spodoptera exigua reveals its significance as a specific Bt target. J Invertebr Pathol 2013; 114:285-91. [DOI: 10.1016/j.jip.2013.09.006] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Revised: 09/04/2013] [Accepted: 09/11/2013] [Indexed: 01/19/2023]
|