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Zhang J, Liu M, Wen L, Hua Y, Zhang R, Li S, Zafar J, Pang R, Xu H, Xu X, Jin F. MiR-2b-3p Downregulated PxTrypsin-9 Expression in the Larval Midgut to Decrease Cry1Ac Susceptibility of the Diamondback Moth, Plutella xylostella (L.). JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2024; 72:2263-2276. [PMID: 38235648 DOI: 10.1021/acs.jafc.3c07678] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2024]
Abstract
Crystal (Cry) toxins, produced by Bacillus thuringiensis, are widely used as effective biological pesticides in agricultural production. However, insects always quickly evolve adaptations against Cry toxins within a few generations. In this study, we focused on the Cry1Ac protoxin activated by protease. Our results identified PxTrypsin-9 as a trypsin gene that plays a key role in Cry1Ac virulence in Plutella xylostella larvae. In addition, P. xylostella miR-2b-3p, a member of the micoRNA-2 (miR-2) family, was significantly upregulated by Cry1Ac protoxin and targeted to PxTrypsin-9 downregulated its expression. The mRNA level of PxTrypsin-9, regulated by miR-2b-3p, revealed an increased tolerance of P. xylostella larvae to Cry1Ac at the post-transcriptional level. Considering that miR-2b and trypsin genes are widely distributed in various pest species, our study provides the basis for further investigation of the roles of miRNAs in the regulation of the resistance to Cry1Ac and other insecticides.
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Affiliation(s)
- Jie Zhang
- National Key Laboratory of Green Pesticide, College of Plant Protection, South China Agricultural University, Guangzhou 510642, China
| | - Mingyou Liu
- National Key Laboratory of Green Pesticide, College of Plant Protection, South China Agricultural University, Guangzhou 510642, China
| | - Liang Wen
- National Key Laboratory of Green Pesticide, College of Plant Protection, South China Agricultural University, Guangzhou 510642, China
| | - Yanyan Hua
- National Key Laboratory of Green Pesticide, College of Plant Protection, South China Agricultural University, Guangzhou 510642, China
| | - Ruonan Zhang
- National Key Laboratory of Green Pesticide, College of Plant Protection, South China Agricultural University, Guangzhou 510642, China
| | - ShuZhong Li
- National Key Laboratory of Green Pesticide, College of Plant Protection, South China Agricultural University, Guangzhou 510642, China
| | - Junaid Zafar
- National Key Laboratory of Green Pesticide, College of Plant Protection, South China Agricultural University, Guangzhou 510642, China
| | - Rui Pang
- National Key Laboratory of Green Pesticide, College of Plant Protection, South China Agricultural University, Guangzhou 510642, China
| | - Hanhong Xu
- National Key Laboratory of Green Pesticide, College of Plant Protection, South China Agricultural University, Guangzhou 510642, China
| | - Xiaoxia Xu
- National Key Laboratory of Green Pesticide, College of Plant Protection, South China Agricultural University, Guangzhou 510642, China
| | - Fengliang Jin
- National Key Laboratory of Green Pesticide, College of Plant Protection, South China Agricultural University, Guangzhou 510642, China
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Zhang C, Wei J, Naing ZL, Soe ET, Tang J, Liang G. Up-regulated serpin gene involved in Cry1Ac resistance in Helicoverpa armigera. PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 2022; 188:105269. [PMID: 36464374 DOI: 10.1016/j.pestbp.2022.105269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Revised: 09/29/2022] [Accepted: 10/15/2022] [Indexed: 06/17/2023]
Abstract
Insect resistance to Bacillus thuringiensis (Bt) is a critical limiting factor for applying the Bt crops. Some studies indicated that decreased protoxin activation because of lower enzymatic activities of trypsin and chymotrypsin and increased expression of serpin might involve in Bt resistance. Our previous study identified an endogenous serpin could inhibit the midgut proteases to activate Cry1Ac and reduce the insecticide activity to Helicoverpa armigera. We hypothesis that up-regulated serpin involve in resistance via inhibiting enzymatic activities of trypsin and chymotrypsin to decrease protoxin activation. Herein, we found the serpin-e gene relative expression in midgut was significantly higher in the LF30 resistant strain than that in the susceptible strain during all developmental stages. Importantly, RNAi-mediated silencing of serpin-e gene expression caused 4.46-fold mortality changes in LF30 strain, but the trypsin and chymotrypsin proteases activities were only changed 0.79-fold and 2.22-fold. In addition, although proteases activities were significantly lower in LF30 strain than that in the susceptible strain, the resistance ratios of LF30 to Cry1Ac protoxin and to activated Cry1Ac toxin were no difference. The results indicated serpins caused insect resistance to Cry1Ac protoxins partly through inhibiting the trypsin and chymotrypsin proteases activities, but it also existed other mechanisms in LF30.
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Affiliation(s)
- Caihong Zhang
- State key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, PR China
| | - Jizhen Wei
- College of Plant Protection, Henan Agricultural University, Zhengzhou 450002, PR China
| | - Zaw Lin Naing
- State key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, PR China
| | - Ei Thinzar Soe
- State key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, PR China
| | - Jinrong Tang
- State key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, PR China
| | - Gemei Liang
- State key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, PR China; Western Agricultural Research Center, Chinese Academy of Agricultural Sciences, Changji 831100,PR China.
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Pinos D, Andrés-Garrido A, Ferré J, Hernández-Martínez P. Response Mechanisms of Invertebrates to Bacillus thuringiensis and Its Pesticidal Proteins. Microbiol Mol Biol Rev 2021; 85:e00007-20. [PMID: 33504654 PMCID: PMC8549848 DOI: 10.1128/mmbr.00007-20] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Extensive use of chemical insecticides adversely affects both environment and human health. One of the most popular biological pest control alternatives is bioinsecticides based on Bacillus thuringiensis This entomopathogenic bacterium produces different protein types which are toxic to several insect, mite, and nematode species. Currently, insecticidal proteins belonging to the Cry and Vip3 groups are widely used to control insect pests both in formulated sprays and in transgenic crops. However, the benefits of B. thuringiensis-based products are threatened by insect resistance evolution. Numerous studies have highlighted that mutations in genes coding for surrogate receptors are responsible for conferring resistance to B. thuringiensis Nevertheless, other mechanisms may also contribute to the reduction of the effectiveness of B. thuringiensis-based products for managing insect pests and even to the acquisition of resistance. Here, we review the relevant literature reporting how invertebrates (mainly insects and Caenorhabditis elegans) respond to exposure to B. thuringiensis as either whole bacteria, spores, and/or its pesticidal proteins.
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Affiliation(s)
- Daniel Pinos
- Instituto Universitario de Biotecnología y Biomedicina (BIOTECMED), Department of Genetics, Universitat de València, Burjassot, Spain
| | - Ascensión Andrés-Garrido
- Instituto Universitario de Biotecnología y Biomedicina (BIOTECMED), Department of Genetics, Universitat de València, Burjassot, Spain
| | - Juan Ferré
- Instituto Universitario de Biotecnología y Biomedicina (BIOTECMED), Department of Genetics, Universitat de València, Burjassot, Spain
| | - Patricia Hernández-Martínez
- Instituto Universitario de Biotecnología y Biomedicina (BIOTECMED), Department of Genetics, Universitat de València, Burjassot, Spain
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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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Liu W, Wu L, Wang J, Li X, Jin X, Zhu J. Activity of Vip3Aa1 against Periplaneta americana. Open Life Sci 2020; 15:133-144. [PMID: 33987470 PMCID: PMC8114776 DOI: 10.1515/biol-2020-0014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2018] [Accepted: 12/04/2019] [Indexed: 11/15/2022] Open
Abstract
AbstractBacillus thuringiensis (Bt) is a well-known entomopathogen. In this study, we cloned the vip3Aa1 gene from Bt strain GIM1.147 and investigated the insecticidal activity of Bt Vip3Aa1 protein produced by Escherichia coli against Periplaneta americana and Blattella germanica. The results showed that purified Vip3Aa1 exhibited an LC50 at 24 h against P. americana and B. germanica of 0.182 mg·ml-1 and 0.276 mg·ml-1, respectively. Investigations of its mode of action showed that Vip3Aa1 could be proteolyzed into a 62-kDa toxic protein by P. americana gut-soluble proteases. In addition, Vip3Aa1 caused severe damage to the columnar colon and the midgut, as observed through hematoxylin-eosin staining and scanning electron microscopy. The 62-kDa activated Vip3Aa1 protein could form ion channels in the colon and the midgut in vitro. Based on protease activity analysis, Vip3Aa1 at concentrations of 0.125 mg·ml-1 and 0.031 mg·ml-1 could downregulate the activities of glutathione S-transferase, α-NA esterase, trypsin, and chymotrypsin. This report provides the first description of the activity of Vip3Aa1 toxins toward P. americana and B. germanica and demonstrates that the mechanism through which Vip3Aa1 kills P. americana and B. germanica differs from that involved in the killing of lepidopteran insects.
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Affiliation(s)
- Wenbin Liu
- School of Pharmaceutical Sciences, Southern Medical University,1023 Shatai South Road, Guangzhou510515, P. R. China
- Guangdong Provincial Key Laboratory of Pharmaceutical Bioactive Substances, Guangdong Pharmaceutical University, Guangzhou510006, P. R. China
| | - Lirong Wu
- Guangdong Provincial Key Laboratory of Pharmaceutical Bioactive Substances, Guangdong Pharmaceutical University, Guangzhou510006, P. R. China
| | - Jie Wang
- Guangdong Provincial Key Laboratory of Pharmaceutical Bioactive Substances, Guangdong Pharmaceutical University, Guangzhou510006, P. R. China
| | - Xiaobo Li
- Guangdong Provincial Key Laboratory of Pharmaceutical Bioactive Substances, Guangdong Pharmaceutical University, Guangzhou510006, P. R. China
| | - Xiaobao Jin
- Guangdong Provincial Key Laboratory of Pharmaceutical Bioactive Substances, Guangdong Pharmaceutical University, Guangzhou510006, P. R. China
| | - Jiayong Zhu
- School of Pharmaceutical Sciences, Southern Medical University,1023 Shatai South Road, Guangzhou510515, P. R. China
- Guangdong Provincial Key Laboratory of Pharmaceutical Bioactive Substances, Guangdong Pharmaceutical University, Guangzhou510006, P. R. China
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Guo Z, Gong L, Kang S, Zhou J, Sun D, Qin J, Guo L, Zhu L, Bai Y, Bravo A, Soberón M, Zhang Y. Comprehensive analysis of Cry1Ac protoxin activation mediated by midgut proteases in susceptible and resistant Plutella xylostella (L.). PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 2020; 163:23-30. [PMID: 31973862 DOI: 10.1016/j.pestbp.2019.10.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Revised: 09/21/2019] [Accepted: 10/13/2019] [Indexed: 06/10/2023]
Abstract
Insecticidal Cry toxins produced by Bacillus thuringiensis (Bt) have been widely used to control agricultural pests in both foliage sprays and transgenic crops. Nevertheless, rapid evolution of insect resistance to Cry toxins requires elucidation of the molecular mechanisms involved in Cry resistance. Two proposed models have been described to explain the toxicity of Cry proteins, the classic model states that Cry protoxin is activated by midgut proteases resulting in activated toxin that binds to receptors and forms a pore in the midgut cells triggering larval death, and the newly proposed dual model of the mode of action of Bt Cry toxins states that protoxin and activated toxins may have different mechanisms of action since several resistant strains to activated Cry toxins are still susceptible to the same Cry-protoxin. Protoxin activation by midgut proteases is a key step in both models. Herein, we evaluated Cry1Ac protoxin activation in a susceptible Plutella xylostella (L.) strain (DBM1Ac-S) and in the near-isogenic strain (NIL-R) with high field-evolved Cry1Ac resistance. Previous work showed that Cry1Ac resistance in NIL-R correlates with reduced binding to midgut receptors due to enhanced MAPK signaling pathway and down regulation of ABCC2 receptor. However, reduced midgut trypsin levels and altered midgut protease gene transcription were also observed in the Cry1Ac-resistant field isolated strain that is parent of the NIL-R strain. Therefore, we analyzed the midgut protease activities in both DBM1Ac-S and NIL-R strains. Detection of enzymatic activities showed that caseinolytic protease, trypsin and chymotrypsin activities were not significantly different between the susceptible and resistant strains. Furthermore, treatment with different trypsin or chymotrypsin inhibitors, such as Nα-tosyl-l-lysine chloromethyl ketone (TLCK) or Np-tosyl-L-phenylalanine chloromethyl ketone (TPCK) did not affect the susceptibility to Cry1Ac protoxin of the DBM1Ac-S and NIL-R larvae. Bioassay results indicated that the NIL-R larvae showed similar resistant levels to both Cry1Ac protoxin and trypsin-activated toxin. Taken together, our results demonstrated that high-level field-evolved Cry1Ac resistance in the NIL-R strain is independent of Cry1Ac protoxin activation and the specific protoxin mechanism of action. This discovery will strengthen our comprehensive understanding of the complex mechanistic basis of Bt resistance in different insects.
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Affiliation(s)
- Zhaojiang Guo
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
| | - Lijun Gong
- 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
| | - Junlei Zhou
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Dan Sun
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Jianying Qin
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Le Guo
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Liuhong Zhu
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Yang Bai
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Alejandra Bravo
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca 62250, Morelos, Mexico
| | - Mario Soberón
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca 62250, Morelos, Mexico
| | - Youjun Zhang
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
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Liu S, Wang S, Wu S, Wu Y, Yang Y. Proteolysis activation of Cry1Ac and Cry2Ab protoxins by larval midgut juice proteases from Helicoverpa armigera. PLoS One 2020; 15:e0228159. [PMID: 32004347 PMCID: PMC6994024 DOI: 10.1371/journal.pone.0228159] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Accepted: 01/08/2020] [Indexed: 12/31/2022] Open
Abstract
Proteolytic processing of Bacillus thuringiensis (Bt) Cry protoxins by insect midgut proteases is critical to their insecticidal activities against target insects. Although transgenic Bt cotton expressing Cry1Ac and Cry2Ab proteins have been widely used for control of the cotton bollworm (Helicoverpa armigera) in the field, the proteolytic cleavage sites in the two protoxins targeted by H. armigera midgut proteases are still not clear. In this study, the proteolysis of Cry1Ac and Cry2Ab protoxins by midgut juice prepared from midgut tissue of H. armigera larvae was investigated. Cleavage of Cry1Ac protoxin by midgut proteases formed a major protein fragment of ~65 kDa, and N-terminal sequencing revealed that cleavage occurred at Arg28 in the fore-end of helix α-1 in domain I of Cry1Ac. Cleavage of Cry2Ab protoxin by midgut juice proteases produced a major protein fragment of ~50 kDa, and the cleavage occurred at Arg139 between helices α-3 and α-4 in domain I of Cry2Ab. The amino acids Arg28 of Cry1Ac and Arg139 of Cry2Ab were predicted as putative trypsin cleavage sites. Bioassay data showed that the toxicities (LC50s) of Cry1Ac and Cry2Ab protoxins were equivalent to those of their respective midgut juice-activated toxins in the susceptible SCD strain of H. armigera. Identification of the exact sites of N-terminal activation of Cry1Ac and Cry2Ab protoxins will provide a basis for a better understanding of the mode of action and resistance mechanisms based on aberrant activation of these protoxins in H. armigera.
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Affiliation(s)
- Shaoyan Liu
- College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Shuo Wang
- College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Shuwen Wu
- College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Yidong Wu
- College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Yihua Yang
- College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu, China
- * E-mail:
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Zhang M, Wei J, Ni X, Zhang J, Jurat-Fuentes JL, Fabrick JA, Carrière Y, Tabashnik BE, Li X. Decreased Cry1Ac activation by midgut proteases associated with Cry1Ac resistance in Helicoverpa zea. PEST MANAGEMENT SCIENCE 2019; 75:1099-1106. [PMID: 30264537 DOI: 10.1002/ps.5224] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Revised: 09/19/2018] [Accepted: 09/22/2018] [Indexed: 06/08/2023]
Abstract
BACKGROUND Field-evolved resistance of Helicoverpa zea to Bacillus thuringiensis (Bt) toxin Cry1Ac was first reported more than a decade ago, yet the underlying mechanisms remain elusive. Towards understanding the mechanisms of resistance to Cry1Ac, we analyzed a susceptible (LAB-S) and two resistant (GA and GA-R) strains of H. zea. The GA strain was derived from Georgia and exposed to Bt toxins only in the field. The GA-R strain was derived from the GA strain and selected for increased resistance to Cry1Ac in the laboratory. RESULTS Resistance to MVPII, a liquid formulation containing a hybrid protoxin similar to Cry1Ac, was 110-fold for GA-R and 7.8-fold for GA relative to LAB-S. In midgut brush border membrane vesicles, activity of alkaline phosphatase and aminopeptidase N did not vary significantly among strains. The activity of total proteases, trypsin-like proteases and chymotrypsin-like proteases was significantly lower for GA-R and GA than LAB-S, but did not differ between GA-R and GA. When H. zea midgut cells were exposed to Cry1Ac protoxin that had been digested with midgut extracts, toxicity was significantly lower for extracts from GA-R and GA relative to extracts from LAB-S, but did not differ between GA-R and GA. Transcriptional analysis showed that none of the five protease genes examined was associated with the decline in Cry1Ac activation in GA-R and GA relative to LAB-S. CONCLUSION The results suggest that decreased Cry1Ac activation is a contributing field-selected mechanism of resistance that helps explain the reduced susceptibility of the GA-R and GA strains. Relative to the LAB-S strain, the two Cry1Ac-resistant strains had lower total protease, trypsin and chymotrypsin activities, a lower Cry1Ac activation rate, and Cry1Ac protoxin incubated with their midgut extracts was less toxic to H. zea midgut cells. © 2018 Society of Chemical Industry.
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Affiliation(s)
- Min Zhang
- School of Life Sciences, Zhengzhou University, Zhengzhou, China
- Department of Entomology, University of Arizona, Tucson, AZ
| | - Jizhen Wei
- Department of Entomology, University of Arizona, Tucson, AZ
- State Key Laboratory for Biology of Plant Disease 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
| | - Jie Zhang
- State Key Laboratory for Biology of Plant Disease and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Juan L Jurat-Fuentes
- Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN, USA
| | - Jeffrey A Fabrick
- USDA-ARS, U.S. Arid Land Agricultural Research Center, Maricopa, AZ, USA
| | - Yves Carrière
- Department of Entomology, University of Arizona, Tucson, AZ
- BIO5 Institute, University of Arizona, Tucson, AZ, USA
| | | | - Xianchun Li
- Department of Entomology, University of Arizona, Tucson, AZ
- BIO5 Institute, University of Arizona, Tucson, AZ, USA
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Jin M, Liao C, Chakrabarty S, Wu K, Xiao Y. Comparative Proteomics of Peritrophic Matrix Provides an Insight into its Role in Cry1Ac Resistance of Cotton Bollworm Helicoverpa armigera. Toxins (Basel) 2019; 11:E92. [PMID: 30717423 PMCID: PMC6409725 DOI: 10.3390/toxins11020092] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2019] [Revised: 01/26/2019] [Accepted: 01/29/2019] [Indexed: 12/25/2022] Open
Abstract
Crystalline (Cry) proteins from Bacillus thuringiensis (Bt) are widely used in sprays and transgenic crops to control insect pests, but the evolution of insect resistance threatens their long-term use. Different resistance mechanisms have been identified, but some have not been completely elucidated. Here, the transcriptome of the midgut and proteome of the peritrophic matrix (PM) were comparatively analyzed to identify potential mechanism of resistance to Cry1Ac in laboratory-selected strain XJ10 of Helicoverpa armigera. This strain had a 146-fold resistance to Cry1Ac protoxin and 45-fold resistance to Cry1Ac activated toxin compared with XJ strain. The mRNA and protein levels for several trypsin genes were downregulated in XJ10 compared to the susceptible strain XJ. Furthermore, 215 proteins of the PM were identified, and nearly all had corresponding mRNAs in the midgut. These results provide new insights that the PM may participate in Bt resistance.
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Affiliation(s)
- Minghui Jin
- Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen 518120, China.
- The State Key Laboratory for Biology of Plant Disease and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, West Yuanmingyuan Road, Beijing, 100193, China.
| | - Chongyu Liao
- Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen 518120, China.
| | - Swapan Chakrabarty
- Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen 518120, China.
| | - Kongming Wu
- The State Key Laboratory for Biology of Plant Disease and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, West Yuanmingyuan Road, Beijing, 100193, China.
| | - Yutao Xiao
- Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen 518120, China.
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Abdelgaffar HM, Oppert C, Sun X, Monserrate J, Jurat-Fuentes JL. Differential heliothine susceptibility to Cry1Ac associated with gut proteolytic activity. PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 2019; 153:1-8. [PMID: 30744882 DOI: 10.1016/j.pestbp.2018.10.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Revised: 09/26/2018] [Accepted: 10/04/2018] [Indexed: 06/09/2023]
Abstract
The Cry1Ac protein is the most active insecticidal toxin from the bacterium Bacillus thuringiensis (Bt) to members of the heliothinae subfamily in Lepidoptera, which includes some of the most devastating pests of corn and cotton worldwide. However, there are wide discrepancies in susceptibility among members of this subfamily in the US. Specifically, susceptibility to Cry1Ac in Helicoverpa zea (Hz) is >100-fold lower when compared to Heliothis virescens (Hv) larvae. The biochemical properties and Cry1Ac protoxin processing activity of gut digestive fluids from larvae of Hz and Hv were compared to test their role in differential susceptibility to Cry1Ac. Comparatively lower protease activity, associated with slower Cry1Ac proteolytic processing, was detected in digestive fluids of Hz compared to Hv. Moreover, Cry1Ac toxin processed by Hz digestive fluids displayed significantly lower toxicity in vitro against cultured insect cells compared to toxin activated by Hv proteases. These data support a contributing role for gut proteases in differential susceptibility to Cry1Ac in heliothine larvae.
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Affiliation(s)
- Heba M Abdelgaffar
- Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN 37996, USA
| | - Cris Oppert
- Bayer CropScience, Morrisville, NC 27709, USA
| | - Xiaocun Sun
- Research Computing Support, Office of Information and Technology, University of Tennessee, Knoxville, TN 37996, USA
| | | | - Juan Luis Jurat-Fuentes
- Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN 37996, USA..
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Garcia‐Ramon DC, Berry C, Tse C, Fernández‐Fernández A, Osuna A, Vílchez S. The parasporal crystals of Bacillus pumilus strain 15.1: a potential virulence factor? Microb Biotechnol 2018; 11:302-316. [PMID: 29027367 PMCID: PMC5812249 DOI: 10.1111/1751-7915.12771] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Accepted: 06/14/2017] [Indexed: 12/02/2022] Open
Abstract
Bacillus pumilus strain 15.1 was previously found to cause larval mortality in the Med-fly Ceratitis capitata and was shown to produce crystals in association with the spore. As parasporal crystals are well-known as invertebrate-active toxins in entomopathogenic bacteria such as Bacillus thuringiensis (Cry and Cyt toxins) and Lysinibacillus sphaericus (Bin and Cry toxins), the B. pumilus crystals were characterized. The crystals were composed of a 45 kDa protein that was identified as an oxalate decarboxylase by peptide mass fingerprinting, N-terminal sequencing and by comparison with the genome sequence of strain 15.1. Synthesis of crystals by a plasmid-cured derivative of strain 15.1 (produced using a novel curing strategy), demonstrated that the oxalate decarboxylase was encoded chromosomally. Crystals spontaneously solubilized when kept at low temperatures, and the protein produced was resistant to trypsin treatment. The insoluble crystals produced by B. pumilus 15.1 did not show significant toxicity when bioassayed against C. capitata larvae, but once the OxdD protein was solubilized, an increase of toxicity was observed. We also demonstrate that the OxdD present in the crystals has oxalate decarboxylate activity as the formation of formate was detected, which suggests a possible mechanism for B. pumilus 15.1 activity. To our knowledge, the characterization of the B. pumilus crystals as oxalate decarboxylase is the first report of the natural production of parasporal inclusions of an enzyme.
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Affiliation(s)
- Diana C. Garcia‐Ramon
- Institute of BiotechnologyCampus FuentenuevaUniversity of GranadaGranadaSpain
- Present address:
Medical SchoolFaculty of Life, Health and Medical SciencesUniversidad Internacional del EcuadorQuitoEcuador
| | - Colin Berry
- Cardiff School of BiosciencesCardiff UniversityCardiffUK
| | - Carmen Tse
- Cardiff School of BiosciencesCardiff UniversityCardiffUK
| | | | - Antonio Osuna
- Institute of BiotechnologyCampus FuentenuevaUniversity of GranadaGranadaSpain
| | - Susana Vílchez
- Institute of BiotechnologyCampus FuentenuevaUniversity of GranadaGranadaSpain
- Department of Biochemistry and Molecular Biology ICampus FuentenuevaUniversity of GranadaGranadaSpain
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12
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Peterson B, Bezuidenhout CC, Van den Berg J. An Overview of Mechanisms of Cry Toxin Resistance in Lepidopteran Insects. JOURNAL OF ECONOMIC ENTOMOLOGY 2017; 110:362-377. [PMID: 28334065 DOI: 10.1093/jee/tow310] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Indexed: 06/06/2023]
Abstract
Arthropods have the capacity to evolve resistance to insecticides and insecticidal traits in genetically modified crops. Resistance development among Lepidoptera is a common phenomenon, and a repertoire of resistance mechanisms to various Cry toxins have been identified from laboratory, greenhouse, and field studies in this insect order. Elucidation of such resistance mechanisms is crucial for developing IRM (insect resistance management) strategies to ensure sustainable use of genetically modified crops. This mini review provides a comprehensive overview of mechanisms of resistance that have been reported for lepidopteran pests. This study demonstrated that resistance mechanisms are highly complex, and the most common mechanism of resistance is altered binding sites. It is yet to be established whether all these altered binding sites are regulated by an MAPK signaling pathway, which might suggest a universal mechanism of resistance in lepidopterans.
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Affiliation(s)
- B Peterson
- Potchefstroom Campus, North-West University, Potchefstroom, 2531, South Africa (; ; )
| | - C C Bezuidenhout
- Potchefstroom Campus, North-West University, Potchefstroom, 2531, South Africa (; ; )
| | - J Van den Berg
- Potchefstroom Campus, North-West University, Potchefstroom, 2531, South Africa (; ; )
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13
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Regode V, Kuruba S, Mohammad AS, Sharma HC. Isolation and Characterization of Gut Bacterial Proteases Involved in Inducing Pathogenicity of Bacillus thuringiensis Toxin in Cotton Bollworm, Helicoverpa armigera. Front Microbiol 2016; 7:1567. [PMID: 27766093 PMCID: PMC5052264 DOI: 10.3389/fmicb.2016.01567] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Accepted: 09/20/2016] [Indexed: 12/16/2022] Open
Abstract
Bacillus thuringiensis toxin proteins are deployed in transgenic plants for pest management. The present studies were aimed at characterization of gut bacterial proteases involved in activation of inactive Cry1Ac protoxin (pro-Cry1Ac) to active toxin in Helicoverpa armigera. Bacterial strains were isolated from H. armigera midgut and screened for their proteolytic activation toward pro-Cry1Ac. Among 12 gut bacterial isolates seven isolates showed proteolytic activity, and proteases from three isolates (IVS1, IVS2, and IVS3) were found to be involved in the proteolytic conversion of pro-Cry1Ac into active toxin. The proteases from IVS1, IVS2, and IVS3 isolates were purified to 11.90-, 15.50-, and 17.20-fold, respectively. The optimum pH and temperature for gut bacterial protease activity was 8.0 and 40°C. Maximum inhibition of total proteolytic activity was exerted by phenylmethane sulfonyl fluoride followed by EDTA. Fluorescence zymography revealed that proteases from IVS1, IVS2, and IVS3 were chymotrypsin-like and showing protease band at ~15, 65, and 15 kDa, respectively. Active Cry1Ac formed from processing pro-Cry1Ac by gut bacterial proteases exhibited toxicity toward H. armigera. The gut bacterial isolates IVS1, IVS2, and IVS3 showed homology with B. thuringiensis (CP003763.1), Vibrio fischeri (CP000020.2), and Escherichia coli (CP011342.1), respectively. Proteases produced by midgut bacteria are involved in proteolytic processing of B. thuringiensis protoxin and play a major role in inducing pathogenicity of B. thuringiensis toxins in H. armigera.
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Affiliation(s)
- Visweshwar Regode
- Department of Entomology, International Crops Research Institute for the Semi-Arid Tropics, PatancheruIndia; Department of Biochemistry, Gulbarga University, KalaburagiIndia
| | | | - Akbar S Mohammad
- Department of Entomology, International Crops Research Institute for the Semi-Arid Tropics, Patancheru India
| | - Hari C Sharma
- Department of Entomology, International Crops Research Institute for the Semi-Arid Tropics, Patancheru India
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14
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Stalinski R, Laporte F, Tetreau G, Després L. Receptors are affected by selection with each Bacillus thuringiensis israelensis Cry toxin but not with the full Bti mixture in Aedes aegypti. INFECTION GENETICS AND EVOLUTION 2016; 44:218-227. [DOI: 10.1016/j.meegid.2016.07.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Revised: 06/09/2016] [Accepted: 07/08/2016] [Indexed: 12/14/2022]
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15
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A promising HD133-like strain of Bacillus thuringiensis with dual efficiency to the two Lepidopteran pests: Spodoptera littoralis (Noctuidae) and Ephestia kuehniella (Pyralidae). Toxicon 2016; 118:112-20. [DOI: 10.1016/j.toxicon.2016.04.045] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Revised: 04/21/2016] [Accepted: 04/25/2016] [Indexed: 11/20/2022]
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16
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Vélez AM, Vellichirammal NN, Jurat-Fuentes JL, Siegfried BD. Cry1F resistance among lepidopteran pests: a model for improved resistance management? CURRENT OPINION IN INSECT SCIENCE 2016; 15:116-124. [PMID: 27436741 DOI: 10.1016/j.cois.2016.04.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Revised: 04/15/2016] [Accepted: 04/18/2016] [Indexed: 06/06/2023]
Abstract
The Cry1Fa protein from the bacterium Bacillus thuringiensis (Bt) is known for its potential to control lepidopteran pests, especially through transgenic expression in maize and cotton. The maize event TC1507 expressing the cry1Fa toxin gene became commercially available in the United States in 2003 for the management of key lepidopteran pests including the European corn borer, Ostrinia nubilalis, and the fall armyworm, Spodoptera frugiperda. A high-dose/refuge strategy has been widely adopted to delay evolution of resistance to event TC1507 and other transgenic Bt crops. Efficacy of this strategy depends on the crops expressing a high dose of the Bt toxin to targeted pests and adjacent refuges of non-Bt host plants serving as a source of abundant susceptible insects. While this strategy has proved effective in delaying O. nubilalis resistance, field-evolved resistance to event TC1507 has been reported in S. frugiperda populations in Puerto Rico, Brazil, and the southeastern United States. This paper examines available information on resistance to Cry1Fa in O. nubilalis and S. frugiperda and discusses how this information identifies opportunities to refine resistance management recommendations for Bt maize.
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Affiliation(s)
- Ana M Vélez
- University of Nebraska-Lincoln, Department of Entomology, 103 Entomology Hall, Lincoln, NE 68583-0816, United States.
| | - Neetha Nanoth Vellichirammal
- University of Nebraska-Lincoln, Department of Entomology, 103 Entomology Hall, Lincoln, NE 68583-0816, United States
| | - Juan Luis Jurat-Fuentes
- University of Tennessee, Department of Entomology and Plant Pathology, Plant Biotechnology Building, Knoxville, TN 37996, United States
| | - Blair D Siegfried
- University of Florida, Entomology and Nematology Department, Charles Steinmetz Hall, PO Box 110620, Gainesville, FL 32611-0620, United States
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17
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Castagnola A, Jurat-Fuentes JL. Intestinal regeneration as an insect resistance mechanism to entomopathogenic bacteria. CURRENT OPINION IN INSECT SCIENCE 2016; 15:104-10. [PMID: 27436739 PMCID: PMC4957658 DOI: 10.1016/j.cois.2016.04.008] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Revised: 04/11/2016] [Accepted: 04/13/2016] [Indexed: 06/06/2023]
Abstract
The intestinal epithelium of insects is exposed to xenobiotics and entomopathogens during the feeding developmental stages. In these conditions, an effective enterocyte turnover mechanism is highly desirable to maintain integrity of the gut epithelial wall. As in other insects, the gut of lepidopteran larvae have stem cells that are capable of proliferation, which occurs during molting and pathogenic episodes. While much is known on the regulation of gut stem cell division during molting, there is a current knowledge gap on the molecular regulation of gut healing processes after entomopathogen exposure. Relevant information on this subject is emerging from studies of the response to exposure to insecticidal proteins from the bacterium Bacillus thuringiensis (Bt) as model intoxicants. In this work we discuss currently available data on the molecular cues involved in gut stem cell proliferation, insect gut healing, and the implications of enhanced healing as a potential mechanism of resistance against Bt toxins.
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Affiliation(s)
- Anaïs Castagnola
- Center for Insect Science, University of Arizona, Tucson, AZ 85721, USA
| | - Juan Luis Jurat-Fuentes
- Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN 37996, USA.
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18
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Nanoth Vellichirammal N, Wang H, Eyun SI, Moriyama EN, Coates BS, Miller NJ, Siegfried BD. Transcriptional analysis of susceptible and resistant European corn borer strains and their response to Cry1F protoxin. BMC Genomics 2015. [PMID: 26220297 PMCID: PMC4518661 DOI: 10.1186/s12864-015-1751-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Background Despite a number of recent reports of insect resistance to transgenic crops expressing insecticidal toxins from Bacillus thuringiensis (Bt), little is known about the mechanism of resistance to these toxins. The purpose of this study is to identify genes associated with the mechanism of Cry1F toxin resistance in European corn borer (Ostrinia nubilalis Hübner). For this, we compared the global transcriptomic response of laboratory selected resistant and susceptible O. nubilalis strain to Cry1F toxin. We further identified constitutive transcriptional differences between the two strains. Results An O. nubilalis midgut transcriptome of 36,125 transcripts was assembled de novo from 106 million Illumina HiSeq and Roche 454 reads and used as a reference for estimation of differential gene expression analysis. Evaluation of gene expression profiles of midgut tissues from the Cry1F susceptible and resistant strains after toxin exposure identified a suite of genes that responded to the toxin in the susceptible strain (n = 1,654), but almost 20-fold fewer in the resistant strain (n = 84). A total of 5,455 midgut transcripts showed significant constitutive expression differences between Cry1F susceptible and resistant strains. Transcripts coding for previously identified Cry toxin receptors, cadherin and alkaline phosphatase and proteases were also differentially expressed in the midgut of the susceptible and resistant strains. Conclusions Our current study provides a valuable resource for further molecular characterization of Bt resistance and insect response to Cry1F toxin in O. nubilalis and other pest species. Electronic supplementary material The online version of this article (doi:10.1186/s12864-015-1751-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | - Haichuan Wang
- Department of Entomology, University of Nebraska-Lincoln, Lincoln, NE, USA.
| | - Seong-Il Eyun
- Center for Biotechnology, University of Nebraska-Lincoln, Lincoln, NE, USA.
| | - Etsuko N Moriyama
- School of Biological Sciences and Center for Plant Science Innovation, University of Nebraska-Lincoln, Lincoln, NE, USA.
| | - Brad S Coates
- USDA-ARS, Corn Insects and Crop Genetics Research Unit, Ames, IA, USA.
| | - Nicholas J Miller
- Department of Entomology, University of Nebraska-Lincoln, Lincoln, NE, USA.
| | - Blair D Siegfried
- Department of Entomology, University of Nebraska-Lincoln, Lincoln, NE, USA.
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19
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Evidence of two mechanisms involved in Bacillus thuringiensis israelensis decreased toxicity against mosquito larvae: Genome dynamic and toxins stability. Microbiol Res 2015; 176:48-54. [DOI: 10.1016/j.micres.2015.04.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Revised: 04/07/2015] [Accepted: 04/17/2015] [Indexed: 11/23/2022]
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20
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Xu LN, Wang YQ, Wang ZY, Hu BJ, Ling YH, He KL. Transcriptome differences between Cry1Ab resistant and susceptible strains of Asian corn borer. BMC Genomics 2015; 16:173. [PMID: 25886725 PMCID: PMC4406038 DOI: 10.1186/s12864-015-1362-2] [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: 09/12/2014] [Accepted: 02/19/2015] [Indexed: 01/09/2023] Open
Abstract
Background Asian corn borer (ACB), Ostrinia furnacalis (Guenée), is the major insect pest of maize in China and countries of East and Southeast Asia, the Pacific and Australasia. ACB can develop strong resistance to the transgenic Bt maize expressing Cry1Ab, the most widely commercialized Bt maize worldwide. However, the molecular basis for the resistance mechanisms of ACB to Cry1Ab remained unclear. Two biological replicates of the transcriptome of Bt susceptible (ACB-BtS) and Cry1Ab resistant (ACB-AbR) strains of ACB were sequenced using Solexa/Illumina RNA-Seq technology to identify Cry1Ab resistance-relevant genes. Results The numbers of unigenes for two biological replications were 63,032 and 53,710 for ACB-BtS and 57,770 and 54,468 for ACB-AbR. There were 35,723 annotated unigenes from ACB reads found by BLAST searching NCBI non-redundant, NCBI non-redundant nucleotide, Swiss-prot protein, Kyoto Encyclopedia of Genes and Genomes, Cluster of Orthologous Groups of proteins, and Gene Ontology databases. Based on the NOISeq method, 3,793 unigenes were judged to be differentially expressed between ACB-BtS and ACB-AbR. Cry1Ab resistance appeared to be associated with change in the transcription level of enzymes involved in growth regulation, detoxification and metabolic/catabolic process. Among previously described Bt toxin receptors, the differentially expressed unigenes associated with aminopeptidase N and chymotrypsin/trypsin were up-regulated in ACB-AbR. Whereas, other putative Cry receptors, cadherin-like protein, alkaline phosphatase, glycolipid, actin, V-type proton ATPase vatalytic, heat shock protein, were under-transcripted. Finally, GPI-anchor biosynthesis was found to be involved in the significantly enriched pathway, and all genes mapped to the pathway were substantially down-regulated in ACB-AbR. Conclusion To our knowledge, this is the first comparative transcriptome study to discover candidate genes involved in ACB Bt resistance. This study identified differentially expressed unigenes related to general Bt resistance in ACB. The assembled, annotated transcriptomes provides a valuable genomic resource for further understanding of the molecular basis of ACB Bt resistance mechanisms. Electronic supplementary material The online version of this article (doi:10.1186/s12864-015-1362-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Li-Na Xu
- Institute of Plant Protection and Agro-Products Safety, Anhui Academy of Agricultural Sciences, Hefei, Anhui, 230031, China. .,The State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China.
| | - Yue-Qin Wang
- The State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China.
| | - Zhen-Ying Wang
- The State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China.
| | - Ben-Jin Hu
- Institute of Plant Protection and Agro-Products Safety, Anhui Academy of Agricultural Sciences, Hefei, Anhui, 230031, China.
| | - Ying-Hui Ling
- College of Animal Science and Technology, Anhui Agricultural University, Hefei, Anhui, 230036, China.
| | - Kang-Lai He
- The State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China.
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21
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Siegwart M, Graillot B, Blachere Lopez C, Besse S, Bardin M, Nicot PC, Lopez-Ferber M. Resistance to bio-insecticides or how to enhance their sustainability: a review. FRONTIERS IN PLANT SCIENCE 2015; 6:381. [PMID: 26150820 PMCID: PMC4472983 DOI: 10.3389/fpls.2015.00381] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Accepted: 05/12/2015] [Indexed: 05/12/2023]
Abstract
After more than 70 years of chemical pesticide use, modern agriculture is increasingly using biological control products. Resistances to conventional insecticides are wide spread, while those to bio-insecticides have raised less attention, and resistance management is frequently neglected. However, a good knowledge of the limitations of a new technique often provides greater sustainability. In this review, we compile cases of resistance to widely used bio-insecticides and describe the associated resistance mechanisms. This overview shows that all widely used bio-insecticides ultimately select resistant individuals. For example, at least 27 species of insects have been described as resistant to Bacillus thuringiensis toxins. The resistance mechanisms are at least as diverse as those that are involved in resistance to chemical insecticides, some of them being common to bio-insecticides and chemical insecticides. This analysis highlights the specific properties of bio-insecticides that the scientific community should use to provide a better sustainability of these products.
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Affiliation(s)
- Myriam Siegwart
- Institut National de la Recherche Agronomique, UR1115, Plantes et Systèmes de Culture Horticoles UnitAvignon, France
- *Correspondence: Myriam Siegwart, Institut National de la Recherche Agronomique, – Plantes et Systèmes de Culture Horticoles Unit – Bât B, 228 Route de L'aérodrome, CS 40509, Domaine St Paul – Site Agroparc, 84914 Avignon, France
| | - Benoit Graillot
- Laboratoire de Génie de l'Environnement Industriel, Ecole des Mines d'Alès, Institut Mines-Telecom et Université de Montpellier Sud de FranceAlès, France
- Natural Plant Protection, Arysta LifeScience GroupPau, France
| | | | - Samantha Besse
- Natural Plant Protection, Arysta LifeScience GroupPau, France
| | - Marc Bardin
- Institut National de la Recherche Agronomique, UR407, Plant Pathology UnitMontfavet, France
| | - Philippe C. Nicot
- Institut National de la Recherche Agronomique, UR407, Plant Pathology UnitMontfavet, France
| | - Miguel Lopez-Ferber
- Laboratoire de Génie de l'Environnement Industriel, Ecole des Mines d'Alès, Institut Mines-Telecom et Université de Montpellier Sud de FranceAlès, France
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22
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Liu C, Xiao Y, Li X, Oppert B, Tabashnik BE, Wu K. Cis-mediated down-regulation of a trypsin gene associated with Bt resistance in cotton bollworm. Sci Rep 2014; 4:7219. [PMID: 25427690 PMCID: PMC4245529 DOI: 10.1038/srep07219] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Accepted: 11/06/2014] [Indexed: 01/02/2023] Open
Abstract
Transgenic plants producing insecticidal proteins from the bacterium Bacillus thuringiensis (Bt) are useful for pest control, but their efficacy is reduced when pests evolve resistance. Here we examined the mechanism of resistance to Bt toxin Cry1Ac in the laboratory-selected LF5 strain of the cotton bollworm, Helicoverpa armigera. This strain had 110-fold resistance to Cry1Ac protoxin and 39-fold resistance to Cry1Ac activated toxin. Evaluation of five trypsin genes revealed 99% reduced transcription of one trypsin gene (HaTryR) was associated with resistance. Silencing of this gene with RNA interference in susceptible larvae increased their survival on diets containing Cry1Ac. Bioassays of progeny from crosses revealed that resistance to Cry1Ac was genetically linked with HaTryR. We identified mutations in the promoter region of HaTryR in the resistant strain. In transfected insect cell lines, transcription was lower when driven by the resistant promoter compared with the susceptible promoter, implicating cis-mediated down-regulation of HaTryR transcription as a mechanism of resistance. The results suggest that H. armigera can adapt to Bt toxin Cry1Ac by decreased expression of trypsin. Because trypsin activation of protoxin is a critical step in toxicity, transgenic plants with activated toxins rather than protoxins might increase the durability of Bt crops.
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Affiliation(s)
- Chenxi Liu
- The State Key Laboratory for Biology of Plant Disease and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, West Yuanmingyuan Road, Beijing, 100193, China
| | - Yutao Xiao
- The State Key Laboratory for Biology of Plant Disease and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, West Yuanmingyuan Road, Beijing, 100193, China
| | - Xianchun Li
- Department of Entomology, University of Arizona, Tucson, AZ 85721, USA
| | - Brenda Oppert
- USDA Agricultural Research Service Center for Grain and Animal Health Research, 1515 College Avenue, Manhattan, KS 66502, USA
| | - Bruce E Tabashnik
- Department of Entomology, University of Arizona, Tucson, AZ 85721, USA
| | - Kongming Wu
- The State Key Laboratory for Biology of Plant Disease and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, West Yuanmingyuan Road, Beijing, 100193, China
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23
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Chen Y, Li M, Islam I, You L, Wang Y, Li Z, Ling L, Zeng B, Xu J, Huang Y, Tan A. Allelic-specific expression in relation to Bombyx mori resistance to Bt toxin. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2014; 54:53-60. [PMID: 25123097 DOI: 10.1016/j.ibmb.2014.07.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Revised: 07/21/2014] [Accepted: 07/23/2014] [Indexed: 06/03/2023]
Abstract
Understanding the mechanism of Bt resistance is one of the key elements of the effective application of Bt in pest control. The lepidopteran model insect, the silkworm, demonstrates qualities that make it an ideal species to use in achieving this understanding. We screened 45 strains of silkworm (Bombyx mori) using a Cry1Ab toxin variant. The sensitivity levels of the strains varied over a wide range. A resistant strain (P50) and a phylogenetically related susceptible strain (Dazao) were selected to profile the expressions of 12 Bt resistance-related genes. The SNPs in these genes were detected based on EST analysis and were validated by allelic-specific PCR. A comparison of allelic-specific expression between P50 and Dazao showed that the transcript levels of heterozygous genes containing two alleles rather than an imbalanced allelic expression contribute more to the resistance of P50 against Bt. The responses of the allelic-specific expression to Bt in hybrid larvae were then investigated. The results showed that the gene expression pattern of an ATP-binding cassette transporter C2 (ABCC2) and an aminopeptidase N (APN3), changed in an allelic-specific manner, with the increase of the resistant allele expression correlated with larval survival. The results suggest that a trans-regulatory mechanism in ABCC2 and APN3 allelic-specific expression is involved in the insect's response to the Bt toxin. The potential role of allelic-specific gene regulation in insect resistance to Bt toxins is discussed.
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Affiliation(s)
- Yazhou Chen
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Muwang Li
- Sericultural Research Institute, Jiangsu University of Science and Technology, Zhengjiang 212018, Jiangsu, China; Sericultural Research Institute, Chinese Academy of Agricultural Sciences, Zhengjiang 212018, Jiangsu, China
| | - Iftakher Islam
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Lang You
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Yueqiang Wang
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Zhiqian Li
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Lin Ling
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Baosheng Zeng
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Jun Xu
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Yongping Huang
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Anjiang Tan
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
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24
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Després L, Stalinski R, Tetreau G, Paris M, Bonin A, Navratil V, Reynaud S, David JP. Gene expression patterns and sequence polymorphisms associated with mosquito resistance to Bacillus thuringiensis israelensis toxins. BMC Genomics 2014; 15:926. [PMID: 25341495 PMCID: PMC4223840 DOI: 10.1186/1471-2164-15-926] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Accepted: 10/16/2014] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Despite the intensive use of Bacillus thuringiensis israelensis (Bti) toxins for mosquito control, little is known about the long term effect of exposure to this cocktail of toxins on target mosquito populations. In contrast to the many cases of resistance to Bacillus thuringiensis Cry toxins observed in other insects, there is no evidence so far for Bti resistance evolution in field mosquito populations. High fitness costs measured in a Bti selected mosquito laboratory strain suggest that evolving resistance to Bti is costly. The aim of the present study was to identify transcription level and polymorphism variations associated with resistance to Bti toxins in the dengue vector Aedes aegypti. We used RNA sequencing (RNA-seq) for comparing a laboratory-selected strain showing elevated resistance to Bti toxins and its parental non-selected susceptible strain. As the resistant strain displayed two marked larval development phenotypes (slow and normal), each phenotype was analyzed separately in order to evidence potential links between resistance mechanisms and mosquito life-history traits. RESULTS A total of 12,458 genes were detected of which 844 were differentially transcribed between the resistant and susceptible strains. Polymorphism analysis revealed a total of 68,541 SNPs of which 12,571 SNPs exhibited more than 40% frequency difference between the resistant and susceptible strains, affecting 2,953 genes. Bti resistance is associated with changes in the transcription level of enzymes involved in detoxification and chitin metabolism. Among previously described Bti-toxin receptors, four alkaline phosphatases (ALPs) were differentially transcribed between resistant and susceptible larvae, and non-synonymous changes affected the protein sequence of one cadherin, six aminopeptidases (APNs) and four α-amylases. Other putative Cry receptors located in lipid rafts, such as flotillin and glycoside hydrolases, were under-transcribed and/or contained non-synonymous substitutions. Finally, immunity-related genes showed contrasted transcription and polymorphisms patterns between the two developmental resistant phenotypes, suggesting the existence of trade-offs between Bti-resistance, life-history traits and immunity. CONCLUSIONS The present study is the first to analyze the whole transcriptome of Bti-resistant mosquitoes by RNA-seq, shedding light on the importance of studying both transcription levels and sequence polymorphism variations to get a comprehensive view of insecticide resistance.
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Affiliation(s)
- Laurence Després
- Université Grenoble Alpes, Laboratoire d'Ecologie Alpine UMR5553, Grenoble, France.
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Ben Hamadou-Charfi D, Sauer AJ, Abdelkefi-Mesrati L, Tounsi S, Jaoua S, Stephan D. Susceptibility of Agrotis segetum (noctuidae) to Bacillus thuringiensis and analysis of midgut proteinases. Prep Biochem Biotechnol 2014; 45:411-20. [PMID: 24839868 DOI: 10.1080/10826068.2014.923449] [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: 10/25/2022]
Abstract
Seventy-eight Bacillus thuringiensis isolates were selected for a screening against the Lepidoptera species Agrotis segetum to search the higher insecticidal activity. In a preliminary bioassay, the spore-crystal mixture of 78 B. thuringiensis isolates was tested against L1 larvae of A. segetum. Fifty-two isolates had more than 60% corrected mortality after 3 days. Seven isolates caused a corrected mortality of 100% on A. segetum. Twelve isolates were selected for a second bioassay investigating the effect of the vegetative insecticidal protein (Vip) against third-instar larvae. After 7 days, the weight gain and the larval stage of each larva were recorded. This bioassay showed an aberration in larval growth increases, morphology, and weight gain. After plasmid pattern analysis, the most active strains are most likely B. thuringiensis kurstaki strains expressing the Vip3A toxin. The absence of two proteinase activities observed in the case of Cry1Ac would be the consequence of the difference in susceptibility of A. segetum to the toxins used.
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Zhu YC, Guo Z, Abel C. Cloning eleven midgut trypsin cDNAs and evaluating the interaction of proteinase inhibitors with Cry1Ac against the tobacco budworm, Heliothis virescens (F.) (Lepidoptera: Noctuidae). J Invertebr Pathol 2012; 111:111-20. [PMID: 22824002 DOI: 10.1016/j.jip.2012.07.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Revised: 05/20/2012] [Accepted: 07/11/2012] [Indexed: 11/30/2022]
Abstract
Midgut trypsins are associated with Bt protoxin activation and toxin degradation. Proteinase inhibitors have potential insecticidal toxicity against a wide range of insect species. This study was conducted to evaluate the interaction of proteinase inhibitors with Bt toxin and to examine midgut trypsin gene profile of Heliothis virescens. A sublethal dose (15 ppb) of Cry1Ac, 0.75% soybean trypsin inhibitor, and 0.1% and 0.2% N-α-tosyl-L-lysine chloromethyl ketone significantly suppressed midgut proteinase activities, and resulted in reductions in larval and pupal size and mass. The treatment with inhibitor+Bt suppressed approximately 65% more larval body mass and 21% more enzymatic activities than the inhibitor-only or Bt-only. Eleven trypsin-like cDNAs were sequenced from the midgut of H. virescens. All trypsins contained three catalytic center residues (H(73), D(153), and S(231)), substrate specificity determinant residues (D(225), G(250), and G(261)), and six cysteines for disulfide bridges. These putative trypsins were separated into three distinct groups, indicating the diverse proteinases evolved in this polyphagous insect. These results indicated that the insecticidal activity of proteinase inhibitors may be used to enhance Bt toxicity and delay resistance development.
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Tetreau G, Bayyareddy K, Jones CM, Stalinski R, Riaz MA, Paris M, David JP, Adang MJ, Després L. Larval midgut modifications associated with Bti resistance in the yellow fever mosquito using proteomic and transcriptomic approaches. BMC Genomics 2012; 13:248. [PMID: 22703117 PMCID: PMC3460780 DOI: 10.1186/1471-2164-13-248] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2012] [Accepted: 05/25/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Bacillus thuringiensis var. israelensis (Bti) is a natural larval mosquito pathogen producing pore-forming toxins targeting the midgut of Diptera larvae. It is used worldwide for mosquito control. Resistance mechanisms of an Aedes aegypti laboratory strain selected for 30 generations with field-collected leaf litter containing Bti toxins were investigated in larval midguts at two levels: 1. gene transcription using DNA microarray and RT-qPCR and 2. differential expression of brush border membrane proteins using DIGE (Differential In Gel Electrophoresis). RESULTS Several Bti Cry toxin receptors including alkaline phosphatases and N-aminopeptidases and toxin-binding V-ATPases exhibited altered expression levels in the resistant strain. The under-expression of putative Bti-receptors is consistent with Bt-resistance mechanisms previously described in Lepidoptera. Four soluble metalloproteinases were found under-transcribed together with a drastic decrease of metalloproteinases activity in the resistant strain, suggesting a role in resistance by decreasing the amount of activated Cry toxins in the larval midgut. CONCLUSIONS By combining transcriptomic and proteomic approaches, we detected expression changes at nearly each step of the ingestion-to-infection process, providing a short list of genes and proteins potentially involved in Bti-resistance whose implication needs to be validated. Collectively, these results open the way to further functional analyses to better characterize Bti-resistance mechanisms in mosquitoes.
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Affiliation(s)
- Guillaume Tetreau
- Laboratoire d'Ecologie Alpine, LECA-UMR 5553, Université de Grenoble 1, BP 53, 38041 Grenoble cedex 09, France.
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Cadavid-Restrepo G, Sahaza J, Orduz S. Treatment of an Aedes aegypti colony with the Cry11Aa toxin for 54 generations results in the development of resistance. Mem Inst Oswaldo Cruz 2012; 107:74-9. [DOI: 10.1590/s0074-02762012000100010] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2011] [Accepted: 10/10/2011] [Indexed: 11/22/2022] Open
Affiliation(s)
| | - Jorge Sahaza
- Corporación para Investigaciones Biológicas, Colombia
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van Munster M, le Gleuher M, Pauchet Y, Augustin S, Courtin C, Amichot M, Ffrench-Constant RH, Pauron D. Molecular characterization of three genes encoding aminopeptidases N in the poplar leaf beetle Chrysomela tremulae. INSECT MOLECULAR BIOLOGY 2011; 20:267-278. [PMID: 21205278 DOI: 10.1111/j.1365-2583.2010.01067.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Three genes encoding proteins showing sequence similarity and features typical of insect APNs were characterized in C. tremulae and designed as CtAPN1, CtAPN2 and CtAPN3. Expression analysis of the three C. tremulae APN genes showed that CtAPN2 transcript is more abundant in the fat body, whereas both CtAPN1 and CtAPN3 are specifically expressed in the midgut. Despite a similar genomic organization, lepidopteran and coleopteran APNs are phylogenetically distant, suggesting that APN gene duplication events occurred after these two insect orders split. Sequence and expression comparisons of CtAPN1, CtAPN2 and CtAPN3 cDNAs in a C. tremulae Bacillus thuringiensis (Bt)-susceptible and in a Bt-resistant strain did not show any polymorphism at the amino acid level or difference at the transcription level.
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Affiliation(s)
- M van Munster
- INRA, UMR 1301 Interactions Biotiques et Santé Végétale, Sophia Antipolis, France.
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Jurat-Fuentes JL, Karumbaiah L, Jakka SRK, Ning C, Liu C, Wu K, Jackson J, Gould F, Blanco C, Portilla M, Perera O, Adang M. Reduced levels of membrane-bound alkaline phosphatase are common to lepidopteran strains resistant to Cry toxins from Bacillus thuringiensis. PLoS One 2011; 6:e17606. [PMID: 21390253 PMCID: PMC3046977 DOI: 10.1371/journal.pone.0017606] [Citation(s) in RCA: 121] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2010] [Accepted: 01/29/2011] [Indexed: 12/13/2022] Open
Abstract
Development of insect resistance is one of the main concerns with the use of transgenic crops expressing Cry toxins from the bacterium Bacillus thuringiensis. Identification of biomarkers would assist in the development of sensitive DNA-based methods to monitor evolution of resistance to Bt toxins in natural populations. We report on the proteomic and genomic detection of reduced levels of midgut membrane-bound alkaline phosphatase (mALP) as a common feature in strains of Cry-resistant Heliothis virescens, Helicoverpa armigera and Spodoptera frugiperda when compared to susceptible larvae. Reduced levels of H. virescens mALP protein (HvmALP) were detected by two dimensional differential in-gel electrophoresis (2D-DIGE) analysis in Cry-resistant compared to susceptible larvae, further supported by alkaline phosphatase activity assays and Western blotting. Through quantitative real-time polymerase chain reaction (qRT-PCR) we demonstrate that the reduction in HvmALP protein levels in resistant larvae are the result of reduced transcript amounts. Similar reductions in ALP activity and mALP transcript levels were also detected for a Cry1Ac-resistant strain of H. armigera and field-derived strains of S. frugiperda resistant to Cry1Fa. Considering the unique resistance and cross-resistance phenotypes of the insect strains used in this work, our data suggest that reduced mALP expression should be targeted for development of effective biomarkers for resistance to Cry toxins in lepidopteran pests.
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Affiliation(s)
- Juan Luis Jurat-Fuentes
- Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, Tennessee, United States of America.
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Cotton bollworm resistance to Bt transgenic cotton: A case analysis. SCIENCE CHINA-LIFE SCIENCES 2010; 53:934-41. [DOI: 10.1007/s11427-010-4045-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2010] [Accepted: 06/06/2010] [Indexed: 10/19/2022]
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32
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Yang Y, Zhu YC, Ottea J, Husseneder C, Leonard BR, Abel C, Huang F. Molecular characterization and RNA interference of three midgut aminopeptidase N isozymes from Bacillus thuringiensis-susceptible and -resistant strains of sugarcane borer, Diatraea saccharalis. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2010; 40:592-603. [PMID: 20685334 DOI: 10.1016/j.ibmb.2010.05.006] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2010] [Revised: 05/18/2010] [Accepted: 05/27/2010] [Indexed: 05/29/2023]
Abstract
Aminopeptidase N (APN) proteins located at the midgut epithelium of some lepidopteran species have been implicated as receptors for insecticidal proteins from Bacillus thuringiensis. cDNAs of three APN isoforms, DsAPN1, DsAPN2, and DsAPN3, from Cry1Ab-susceptible (Cry1Ab-SS) and -resistant (Cry1Ab-RR) strains of the sugarcane borer, Diatraea saccharalis (F.) (Lepidoptera: Crambidae), were identified and sequenced using reverse transcriptase polymerase chain reaction (RT-PCR) and 5' rapid amplification of cDNA end (5' RACE). The characteristic APN sequence features were derived from deduced amino acid sequences of the cloned cDNAs. cDNA sequences of the three APN genes were identical between the Cry1Ab-SS and -RR strains. However, total APN proteolytic activity and gene expression of the three APNs from Cry1Ab-RR larvae were significantly lower than those of the Cry1Ab-SS strain. RNA interference (RNAi) was employed using an oral droplet feeding technique for the three APNs of the Cry1Ab-SS strain. Down-regulating expressions of the three APN genes by RNAi were corresponding to the reductions in the specific APN activity. In addition, silencing of all three APNs in D. saccharalis in vivo by RNAi resulted in a decrease in Cry1Ab susceptibility. Our results showed that reduction in expression of the three APNs is functionally associated with the Cry1Ab resistance in D. saccharalis.
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Affiliation(s)
- Yunlong Yang
- Department of Entomology, Louisiana State University Agricultural Center, Baton Rouge, LA 70803, USA
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Sayed A, Wiechman B, Struewing I, Smith M, French W, Nielsen C, Bagley M. Isolation of transcripts from Diabrotica virgifera virgifera LeConte responsive to the Bacillus thuringiensis toxin Cry3Bb1. INSECT MOLECULAR BIOLOGY 2010; 19:381-389. [PMID: 20337747 DOI: 10.1111/j.1365-2583.2010.00998.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Crystal (Cry) proteins derived from Bacillus thuringiensis (Bt) have been widely used as a method of insect pest management for several decades. In recent years, a transgenic corn expressing the Cry3Bb1 toxin has been successfully used for protection against corn rootworm larvae (genus Diabrotica). The biological action of the Bt toxin in corn rootworms has not yet been clearly defined. Because development of resistance to Bt by corn rootworms will have huge economic and ecological costs, insight into larval response to Bt toxin is highly desirable. We identified 19 unique transcripts that are differentially expressed in D. virgifera virgifera larvae reared on corn transgenic for Cry3Bb1. Putative identities of these genes were consistent with impacts on metabolism and development. Analysis of highly modulated transcripts resulted in the characterization of genes coding for a member of a cysteine-rich secretory protein family and a glutamine-rich membrane protein. A third gene that was isolated encodes a nondescript 132 amino acid protein while a fourth highly modulated transcript could not be further characterized. Expression patterns of these four genes were strikingly different between susceptible and resistant western corn rootworm populations. These genes may provide useful targets for monitoring of Bt exposure patterns and resistance development in pest and non-target insect populations.
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Affiliation(s)
- A Sayed
- Dynamac Corporation c/o US Environmental Protection Agency, Cincinnati, OH 45268, USA.
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Huang L, Cheng T, Xu P, Cheng D, Fang T, Xia Q. A genome-wide survey for host response of silkworm, Bombyx mori during pathogen Bacillus bombyseptieus infection. PLoS One 2009; 4:e8098. [PMID: 19956592 PMCID: PMC2780328 DOI: 10.1371/journal.pone.0008098] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2009] [Accepted: 11/04/2009] [Indexed: 11/18/2022] Open
Abstract
Host-pathogen interactions are complex relationships, and a central challenge is to reveal the interactions between pathogens and their hosts. Bacillus bombysepticus (Bb) which can produces spores and parasporal crystals was firstly separated from the corpses of the infected silkworms (Bombyx mori). Bb naturally infects the silkworm can cause an acute fuliginosa septicaemia and kill the silkworm larvae generally within one day in the hot and humid season. Bb pathogen of the silkworm can be used for investigating the host responses after the infection. Gene expression profiling during four time-points of silkworm whole larvae after Bb infection was performed to gain insight into the mechanism of Bb-associated host whole body effect. Genome-wide survey of the host genes demonstrated many genes and pathways modulated after the infection. GO analysis of the induced genes indicated that their functions could be divided into 14 categories. KEGG pathway analysis identified that six types of basal metabolic pathway were regulated, including genetic information processing and transcription, carbohydrate metabolism, amino acid and nitrogen metabolism, nucleotide metabolism, metabolism of cofactors and vitamins, and xenobiotic biodegradation and metabolism. Similar to Bacillus thuringiensis (Bt), Bb can also induce a silkworm poisoning-related response. In this process, genes encoding midgut peritrophic membrane proteins, aminopeptidase N receptors and sodium/calcium exchange protein showed modulation. For the first time, we found that Bb induced a lot of genes involved in juvenile hormone synthesis and metabolism pathway upregulated. Bb also triggered the host immune responses, including cellular immune response and serine protease cascade melanization response. Real time PCR analysis showed that Bb can induce the silkworm systemic immune response, mainly by the Toll pathway. Anti-microorganism peptides (AMPs), including of Attacin, Lebocin, Enbocin, Gloverin and Moricin families, were upregulated at 24 hours post the infection.
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Affiliation(s)
- Lulin Huang
- Institute of Sericulture and Systems Biology, Southwest University, Chongqing, China
- Institute of Economic Crops Breeding and Cultivation, Sichuan Academy of Agricultural Sciences, Chengdu, China
| | - Tingcai Cheng
- Institute of Agronomy and Life Science, Chongqing University, Chongqing, China
| | - Pingzhen Xu
- Institute of Sericulture and Systems Biology, Southwest University, Chongqing, China
| | - Daojun Cheng
- Institute of Sericulture and Systems Biology, Southwest University, Chongqing, China
| | - Ting Fang
- Institute of Sericulture and Systems Biology, Southwest University, Chongqing, China
| | - Qingyou Xia
- Institute of Sericulture and Systems Biology, Southwest University, Chongqing, China
- Institute of Agronomy and Life Science, Chongqing University, Chongqing, China
- * E-mail:
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Schmidt NR, Haywood JM, Bonning BC. Toward the physiological basis for increased Agrotis ipsilon multiple nucleopolyhedrovirus infection following feeding of Agrotis ipsilon larvae on transgenic corn expressing Cry1Fa2. J Invertebr Pathol 2009; 102:141-8. [DOI: 10.1016/j.jip.2009.07.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2009] [Revised: 07/24/2009] [Accepted: 07/27/2009] [Indexed: 11/26/2022]
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Asymmetrical cross-resistance between Bacillus thuringiensis toxins Cry1Ac and Cry2Ab in pink bollworm. Proc Natl Acad Sci U S A 2009; 106:11889-94. [PMID: 19581574 DOI: 10.1073/pnas.0901351106] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Transgenic crops producing Bacillus thuringiensis (Bt) toxins kill some key insect pests and can reduce reliance on insecticide sprays. Sustainable use of such crops requires methods for delaying evolution of resistance by pests. To thwart pest resistance, some transgenic crops produce 2 different Bt toxins targeting the same pest. This "pyramid" strategy is expected to work best when selection for resistance to 1 toxin does not cause cross-resistance to the other toxin. The most widely used pyramid is transgenic cotton producing Bt toxins Cry1Ac and Cry2Ab. Cross-resistance between these toxins was presumed unlikely because they bind to different larval midgut target sites. Previous results showed that laboratory selection with Cry1Ac caused little or no cross-resistance to Cry2A toxins in pink bollworm (Pectinophora gossypiella), a major cotton pest. We show here, however, that laboratory selection of pink bollworm with Cry2Ab caused up to 420-fold cross-resistance to Cry1Ac as well as 240-fold resistance to Cry2Ab. Inheritance of resistance to high concentrations of Cry2Ab was recessive. Larvae from a laboratory strain resistant to Cry1Ac and Cry2Ab in diet bioassays survived on cotton bolls producing only Cry1Ac, but not on cotton bolls producing both toxins. Thus, the asymmetrical cross-resistance seen here does not threaten the efficacy of pyramided Bt cotton against pink bollworm. Nonetheless, the results here and previous evidence indicate that cross-resistance occurs between Cry1Ac and Cry2Ab in some key cotton pests. Incorporating the potential effects of such cross-resistance in resistance management plans may help to sustain the efficacy of pyramided Bt crops.
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Hernández-Martínez P, Ferré J, Escriche B. Broad-spectrum cross-resistance in Spodoptera exigua from selection with a marginally toxic Cry protein. PEST MANAGEMENT SCIENCE 2009; 65:645-650. [PMID: 19253909 DOI: 10.1002/ps.1725] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
BACKGROUND Spodoptera exigua (Hübner) has developed resistance to a wide range of chemical insecticides. Products based on Bacillus thuringiensis Cry toxins are used in integrated pest management as an ecologically friendly alternative for pest control. Since there are few B. thuringiensis Cry proteins highly active against S. exigua, it is desirable to apply appropriate resistance management strategies to prevent the evolution of resistance to these proteins. RESULTS Spodoptera exigua larvae were selected with Cry1Ab, a protein with low activity against this pest. Selected larvae developed > 30-fold resistance to Cry1Ab in 13 generations, relative to an unselected strain. The estimated realised heritability (h(2)) for the first five generations of selection was 0.15. Cross-resistance was also observed to the more active proteins Cry1Ca, Cry1Da and Cry1Fa (>20, 26 and > 8 respectively). The activity of midgut proteases to degrade the ingested toxin was tested, although no differences in activity were found between selected and unselected larvae. CONCLUSION Spodoptera exigua is able to evolve cross-resistance to highly active Cry proteins when exposed to a protein with marginal toxicity to this species. It is important to take this into account in areas where S. exigua is a secondary pest and B. thuringiensis Cry1A toxins are used to control other pests.
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Vinokurov KS, Elpidina EN, Zhuzhikov DP, Oppert B, Kodrik D, Sehnal F. Digestive proteolysis organization in two closely related Tenebrionid beetles: red flour beetle (Tribolium castaneum) and confused flour beetle (Tribolium confusum). ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2009; 70:254-279. [PMID: 19294681 DOI: 10.1002/arch.20299] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The spectra of Tribolium castaneum and T. confusum larval digestive peptidases were characterized with respect to the spatial organization of protein digestion in the midgut. The pH of midgut contents in both species increased from 5.6-6.0 in the anterior to 7.0-7.5 in the posterior midgut. However, the pH optimum of the total proteolytic activity of the gut extract from either insect was pH 4.1. Approximately 80% of the total proteolytic activity was in the anterior and 20% in the posterior midgut of either insect when evaluated in buffers simulating the pH and reducing conditions characteristic for each midgut section. The general peptidase activity of gut extracts from either insect in pH 5.6 buffer was mostly due to cysteine peptidases. In the weakly alkaline conditions of the posterior midgut, the serine peptidase contribution was 31 and 41% in T. castaneum and T. confusum, respectively. A postelectrophoretic peptidase activity assay with gelatin also revealed the important contribution of cysteine peptidases in protein digestion in both Tribolium species. The use of a postelectrophoretic activity assay with p-nitroanilide substrates and specific inhibitors revealed a set of cysteine and serine endopeptidases, 8 and 10 for T. castaneum, and 7 and 9 for T. confusum, respectively. Serine peptidases included trypsin-, chymotrypsin-, and elastase-like enzymes, the latter being for the first time reported in Tenebrionid insects. These data support a complex system of protein digestion in the Tribolium midgut with the fundamental role of cysteine peptidases.
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Affiliation(s)
- K S Vinokurov
- Entomological Institute, Biology Centre AV CR, Ceské Budejovice, Czech Republic; Department of Entomology, Biological Faculty, Moscow State University, Moscow, Russia
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Gassmann AJ, Carrière Y, Tabashnik BE. Fitness costs of insect resistance to Bacillus thuringiensis. ANNUAL REVIEW OF ENTOMOLOGY 2009; 54:147-63. [PMID: 19067630 DOI: 10.1146/annurev.ento.54.110807.090518] [Citation(s) in RCA: 274] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Evolution of resistance by insect pests threatens the continued effectiveness of Bacillus thuringiensis (Bt) toxins in sprays and transgenic crops. Fitness costs of Bt resistance occur when, in the absence of Bt toxins, fitness is lower for resistant insects than for susceptible insects. Modeling results show that fitness costs can delay resistance by selecting against Bt-resistant genotypes in refuges where insects are not exposed to Bt toxins. In 77 studies including 18 species, fitness costs were detected in 62% of experiments testing for declines in resistance and in 34% of fitness component comparisons. Mean fitness costs were 15.5% for survival, 7.4% for development time, and 2.5% for mass. Although most fitness costs were recessive, nonrecessive costs can select more strongly against resistance. Because fitness costs vary with ecological conditions, refuges designed to increase the dominance or magnitude of fitness costs could be especially useful for delaying pest resistance.
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Affiliation(s)
- Aaron J Gassmann
- Department of Entomology, Iowa State University, Ames, Iowa 50011, USA.
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Price DRG, Gatehouse JA. RNAi-mediated crop protection against insects. Trends Biotechnol 2008; 26:393-400. [PMID: 18501983 DOI: 10.1016/j.tibtech.2008.04.004] [Citation(s) in RCA: 320] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2008] [Revised: 04/04/2008] [Accepted: 04/14/2008] [Indexed: 12/18/2022]
Abstract
Downregulation of the expression of specific genes through RNA interference (RNAi), has been widely used for genetic research in insects. The method has relied on the injection of double-stranded RNA (dsRNA), which is not possible for practical applications in crop protection. By contrast, specific suppression of gene expression in nematodes is possible through feeding with dsRNA. This approach was thought to be unfeasible in insects, but recent results have shown that dsRNA fed as a diet component can be effective in downregulating targeted genes. More significantly, expression of dsRNA directed against suitable insect target genes in transgenic plants has been shown to give protection against pests, opening the way for a new generation of insect-resistant crops.
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Affiliation(s)
- Daniel R G Price
- School of Biological and Biomedical Sciences, Durham University, South Road, Durham DH1 3LE, UK
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Budatha M, Meur G, Vimala Devi PS, Kirti PB, Dutta-Gupta A. Characterization of Bacillus thuringiensis strain DOR4 toxic to castor semilooper Achaea janata: proteolytic processing and binding of toxins to receptors. Curr Microbiol 2008; 57:72-7. [PMID: 18437459 DOI: 10.1007/s00284-008-9155-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2007] [Accepted: 01/18/2008] [Indexed: 11/24/2022]
Abstract
We have isolated a strain of Bacillus thuringiensis (Bt) from Indian soil samples that was shown to be toxic to Achaea janata larvae. The isolate, named B. thuringiensis DOR4, serotypically identified with the standard subspecies kurstaki (H3a3b3c) and produced bipyramidal inclusions along with an amorphous type. Although the plasmid pattern of DOR4 was different from that of the reference strain, a crystal protein profile showed the presence of two major bands (130 and 65 kDa) similar to those of Bt subsp. kurstaki HD-1. To verify the cry gene content of DOR4, triplex PCR analysis was performed; it showed amplification of the cry1C gene in addition to cry1Aa, cry1Ac, cry2A, and cry2B genes, but not the cry1Ab gene. RT-PCR analysis showed the expression of cry1Aa and cry1Ac genes. In vitro proteolysis of DOR4 protoxin with midgut extract generated products of different sizes. Zymogram analysis of DOR4 protoxin as substrate pointed to a number of distinct proteases that were responsible for activation of protoxins. Furthermore, toxin overlay analysis revealed the presence of multiple toxin-binding proteins in midgut epithelium. Based on all these characterizations, we suggest that the Bt DOR4 strain can be exploited for an A. janata control program.
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Comparative study of Bacillus thuringiensis Cry1Aa and Cry1Ac delta-endotoxin activation, inactivation and in situ histopathological effect in Ephestia kuehniella (Lepidoptera: Pyralidae). Mol Biotechnol 2007; 38:233-9. [PMID: 18040897 DOI: 10.1007/s12033-007-9021-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2007] [Accepted: 11/08/2007] [Indexed: 10/22/2022]
Abstract
A comparative study of different steps in the mode of action of the individual Bacillus thuringiensis kurstaki BNS3 Cry1Aa and Cry1Ac delta-endotoxins on E. kuehniella larvae was performed in order to investigate the origin of the difference in the response of this larvae to each of the latter. Proteolytic activation was shown to be one of the main steps impaired in E. kuehniella tolerance to Cry1Aa. The absence of two proteinase activities as well as an altered activity level observed in the case of Cry1Aa would be the consequence of proteinase-mediated tolerance of E. kuehniella to this toxin. In situ binding and histopathological effect analyses allowed concluding that the binding of the toxin to BBMV receptors is the key step in E. kuehniella tolerance to Cry1Aa toxin. The latter was slightly bound to apical membranes of epithelial cells that remained intact, whereas Cry1Ac was tightly bound to completely damaged cells basal membranes.
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Production and characterization of Bacillus thuringiensis Cry1Ac-resistant cotton bollworm Helicoverpa zea (Boddie). Appl Environ Microbiol 2007; 74:462-9. [PMID: 18024681 DOI: 10.1128/aem.01612-07] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Laboratory-selected Bacillus thuringiensis-resistant colonies are important tools for elucidating B. thuringiensis resistance mechanisms. However, cotton bollworm, Helicoverpa zea, a target pest of transgenic corn and cotton expressing B. thuringiensis Cry1Ac (Bt corn and cotton), has proven difficult to select for stable resistance. Two populations of H. zea (AR and MR), resistant to the B. thuringiensis protein found in all commercial Bt cotton varieties (Cry1Ac), were established by selection with Cry1Ac activated toxin (AR) or MVP II (MR). Cry1Ac toxin reflects the form ingested by H. zea when feeding on Bt cotton, whereas MVP II is a Cry1Ac formulation used for resistance selection and monitoring. The resistance ratio (RR) for AR exceeded 100-fold after 11 generations and has been maintained at this level for nine generations. This is the first report of stable Cry1Ac resistance in H. zea. MR crashed after 11 generations, reaching only an RR of 12. AR was only partially cross-resistant to MVP II, suggesting that MVP II does not have the same Cry1Ac selection pressure as Cry1Ac toxin against H. zea and that proteases may be involved with resistance. AR was highly cross-resistant to Cry1Ab toxin but only slightly cross-resistant to Cry1Ab expressing corn leaf powder. AR was not cross-resistant to Cry2Aa2, Cry2Ab2-expressing corn leaf powder, Vip3A, and cypermethrin. Toxin-binding assays showed no significant differences, indicating that resistance was not linked to a reduction in binding. These results aid in understanding why this pest has not evolved B. thuringiensis resistance, and highlight the need to choose carefully the form of B. thuringiensis protein used in experiments.
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Budatha M, Meur G, Dutta-Gupta A. Identification and characterization of midgut proteases in Achaea janata and their implications. Biotechnol Lett 2007; 30:305-10. [PMID: 17891457 DOI: 10.1007/s10529-007-9539-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2007] [Revised: 08/30/2007] [Accepted: 08/31/2007] [Indexed: 11/28/2022]
Abstract
Insect midgut proteases are excellent targets for insecticidal agents such as Bacillus thuringiensis Cry toxins and protease inhibitors. The midgut proteases of Achaea janata have been characterized and Casein zymograms indicated at least five distinct activities corresponding to approx 17, 20, 29 and 80, and 90 kDa. Using a combination of synthetic substrates and specific inhibitors in casein zymograms, photometric assays and activity blots, three trypsin-like and one elastase-like serine proteases were identified but no chymotrypsin-like activity. Various proteinase inhibitors displayed differential inhibitory effects towards the midgut proteases.
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Jurat-Fuentes JL, Adang MJ. A proteomic approach to study Cry1Ac binding proteins and their alterations in resistant Heliothis virescens larvae. J Invertebr Pathol 2007; 95:187-91. [PMID: 17467006 DOI: 10.1016/j.jip.2007.01.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2006] [Accepted: 01/20/2007] [Indexed: 12/11/2022]
Abstract
Binding of the Bacillus thuringiensis Cry1Ac toxin to specific receptors in the midgut brush border membrane is required for toxicity. Alteration of these receptors is the most reported mechanism of resistance. We used a proteomic approach to identify Cry1Ac binding proteins from intestinal brush border membrane (BBM) prepared from Heliothis virescens larvae. Cry1Ac binding BBM proteins were detected in 2D blots and identified using peptide mass fingerprinting (PMF) or de novo sequencing. Among other proteins, the membrane bound alkaline phosphatase (HvALP), and a novel phosphatase, were identified as Cry1Ac binding proteins. Reduction of HvALP expression levels correlated directly with resistance to Cry1Ac in the YHD2-B strain of H. virescens. To study additional proteomic alterations in resistant H. virescens larvae, we used two-dimensional differential in-gel electrophoresis (2D-DIGE) to compare three independent resistant strains with a susceptible strain. Our results validate the use of proteomic approaches to identify toxin binding proteins and proteome alterations in resistant insects.
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Affiliation(s)
- Juan L Jurat-Fuentes
- Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN 37996-4560, USA.
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