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Resistance of Cabbage Loopers to Bacillus thuringiensis (Bt) Toxin Cry1F and to Dual-Bt Toxin WideStrike Cotton Plants. Appl Environ Microbiol 2022; 88:e0119422. [PMID: 36200769 PMCID: PMC9599322 DOI: 10.1128/aem.01194-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Cry proteins from Bacillus thuringiensis (Bt) are major insecticidal toxins in formulated Bt sprays and are expressed in genetically engineered Bt crops for insect pest control. However, the widespread application of Bt toxins in the field imposes strong selection pressure on target insects, leading to the evolution of insect resistance to the Bt toxins. Identification and understanding of mechanisms of insect resistance to Bt toxins are an important approach for dissecting the modes of action of Bt toxins and providing knowledge necessary for the development of resistance management technologies. In this study, cabbage looper (Trichoplusia ni) strains resistant to the transgenic dual-Bt toxin WideStrike cotton plants, which express Bt toxins Cry1Ac and Cry1F, were selected from T. ni strains resistant to the Bt formulation Bt-DiPel. The WideStrike-resistant T. ni larvae were confirmed to be resistant to both Bt toxins Cry1Ac and Cry1F. From the WideStrike-resistant T. ni, the Cry1F resistance trait was further isolated to establish a T. ni strain resistant to Cry1F only. The levels of Cry1F resistance in the WideStrike-resistant and the Cry1F-resistant strains were determined, and the inheritance of the Cry1F-resistant trait in the two strains was characterized. Genetic association analysis of the Cry1F resistance trait indicated that the Cry1F resistance in T. ni isolated in this study is not shared with the Cry1Ac resistance mechanism nor is it associated with a mutation in the ABCC2 gene, as has so far been reported in Cry1F-resistant insects. IMPORTANCE Insecticidal toxins from Bacillus thuringiensis (Bt) are highly effective for insect control in agriculture. However, the widespread application of Bt toxins exerts strong selection for Bt resistance in insect populations. The continuing success of Bt biotechnology for pest control requires the identification of resistance and understanding of the mechanisms of resistance to Bt toxins. Cry1F is an important Bt toxin used in transgenic cotton, maize, and soybean varieties adopted widely for insect control. To understand the mode of action of Cry1F and mechanisms of Cry1F resistance in insects, it is important to identify Cry1F-specific resistance and the resistance mechanisms. In this study, Trichoplusia ni strains resistant to commercial "WideStrike" cotton plants that express Bt toxins Cry1Ac and Cry1F were selected, and a Cry1F-specific resistant strain was isolated. The isolation of the novel Cry1F-specific resistance in the T. ni provided an invaluable biological system to discover a Cry1F-specific novel resistance mechanism.
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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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Wei J, Zhang Y, An S. The progress in insect cross-resistance among Bacillus thuringiensis toxins. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2019; 102:e21547. [PMID: 30864250 DOI: 10.1002/arch.21547] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Revised: 02/27/2019] [Accepted: 02/28/2019] [Indexed: 06/09/2023]
Abstract
Bt crop pyramids produce two or more Bt proteins active to broaden the spectrum of action and to delay the development of resistance in exposed insect populations. The cross-resistance between Bt toxins is a vital restriction factor for Bt crop pyramids, which may reduce the effect of pyramid strategy. In this review, the status of the cross-resistance among more than 20 Bt toxins that are most commonly used against 13 insect pests was analyzed. The potential mechanisms of cross-resistance are discussed. The corresponding measures, including pyramid RNA interference and Bt toxin, "high dose/refuge," and so on are advised to be taken for adopting the pyramided strategy to delay the Bt evolution of resistance and control the target pest insect.
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Affiliation(s)
- Jizhen Wei
- State Key Laboratory of Wheat and Maize Crop Science, College of Plant Protection, Henan Agricultural University, Zhengzhou, China
| | - Yaling Zhang
- State Key Laboratory of Wheat and Maize Crop Science, College of Plant Protection, Henan Agricultural University, Zhengzhou, China
- Tibet Academy of Agriculture and Animal Husbandry Sciences, Lhasa, China
| | - Shiheng An
- State Key Laboratory of Wheat and Maize Crop Science, College of Plant Protection, Henan Agricultural University, Zhengzhou, China
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Yang X, Chen W, Song X, Ma X, Cotto-Rivera RO, Kain W, Chu H, Chen YR, Fei Z, Wang P. Mutation of ABC transporter ABCA2 confers resistance to Bt toxin Cry2Ab in Trichoplusia ni. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2019; 112:103209. [PMID: 31422154 DOI: 10.1016/j.ibmb.2019.103209] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Revised: 07/22/2019] [Accepted: 07/24/2019] [Indexed: 05/29/2023]
Abstract
Insecticidal proteins from Bacillus thuringiensis (Bt) are the primary recombinant proteins expressed in transgenic crops (Bt-crops) to confer insect resistance. Development of resistance to Bt toxins in insect populations threatens the sustainable application of Bt-crops in agriculture. The Bt toxin Cry2Ab is a major insecticidal protein used in current Bt-crops, and resistance to Cry2Ab has been selected in several insects, including the cabbage looper, Trichoplusia ni. In this study, the Cry2Ab resistance gene in T. ni was mapped to Chromosome 17 by genetic linkage analyses using a whole genome resequencing approach, and was then finely mapped using RNA-seq-based bulked segregant analysis (BSA) and amplicon sequencing (AmpSeq)-based fine linkage mapping to a locus containing two genes, ABCA1 and ABCA2. Mutations in ABCA1 and ABCA2 in Cry2Ab resistant T. ni were identified by both genomic DNA and cDNA sequencing. Analysis of the expression of ABCA1 and ABCA2 in T. ni larvae indicated that ABCA2 is abundantly expressed in the larval midgut, but ABCA1 is not a midgut-expressed gene. The mutation in ABCA2 in Cry2Ab resistant T. ni was identified to be an insertion of a transposon Tntransib in ABCA2. For confirmation of ABCA2 as the Cry2Ab-resistance gene, T. ni mutants with frameshift mutations in ABCA1 and ABCA2 were generated by CRISPR/Cas9 mutagenesis. Bioassays of the T. ni mutants with Cry2Ab verified that the mutations of ABCA1 did not change larval susceptibility to Cry2Ab, but the ABCA2 mutants were highly resistant to Cry2Ab. Genetic complementation test of the ABCA2 allele in Cry2Ab resistant T. ni with an ABCA2 mutant generated by CRISPR/Cas9 confirmed that the ABCA2 mutation in the Cry2Ab resistant strain confers the resistance. The results from this study confirmed that ABCA2 is essential for the toxicity of Cry2Ab in T. ni and mutation of ABCA2 confers the resistance to Cry2Ab in the resistant T. ni strain derived from a Bt resistant greenhouse population.
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Affiliation(s)
- Xiaowei Yang
- Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY, 14456, USA
| | - Wenbo Chen
- Boyce Thompson Institute, Ithaca, NY, 14853, USA
| | - Xiaozhao Song
- Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY, 14456, USA
| | - Xiaoli Ma
- Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY, 14456, USA
| | - Rey O Cotto-Rivera
- Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY, 14456, USA
| | - Wendy Kain
- Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY, 14456, USA
| | - Hannah Chu
- Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY, 14456, USA; Department of Science, John Jay College of Criminal Justice-City University of New York, New York, NY, 10019, USA
| | - Yun-Ru Chen
- Boyce Thompson Institute, Ithaca, NY, 14853, USA
| | - Zhangjun Fei
- Boyce Thompson Institute, Ithaca, NY, 14853, USA; USDA-Agricultural Research Service, Robert W. Holley Center for Agriculture and Health, Ithaca, NY, 14853, USA
| | - Ping Wang
- Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY, 14456, USA.
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Guo W, Kain W, Wang P. Effects of disruption of the peritrophic membrane on larval susceptibility to Bt toxin Cry1Ac in cabbage loopers. JOURNAL OF INSECT PHYSIOLOGY 2019; 117:103897. [PMID: 31199901 DOI: 10.1016/j.jinsphys.2019.103897] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Revised: 06/05/2019] [Accepted: 06/10/2019] [Indexed: 06/09/2023]
Abstract
The insect midgut peritrophic membrane (or peritrophic matrix) (PM) is an extracellular structure, lining the midgut epithelium. The PM facilitates the food digestion process and plays important roles in insect-microbe interactions as a barrier against microbial pathogens. The soil bacterium, Bacillus thuringiensis (Bt), and its proteinaceous toxins are widely used for insect control. To understand the protective role of PM in insects against Bt toxins, the effect of PM on larval susceptibility to Bt toxin Cry1Ac was examined in Cry1Ac-susceptible and -resistant strains of the cabbage looper, Trichoplusia ni. The PM in T. ni was disrupted, using a baculovirus enhancin (TnGV enhancin) to degrade the major PM mucin protein IIM and a chitin binding chemical, Calcofluor, to inhibit the binding of PM proteins to chitin. Bioassays of the susceptibility of T. ni larvae to Cry1Ac with treatment of TnGV enhancin showed significantly increased larval mortality in both the Cry1Ac susceptible and resistant strains, confirming that the PM is a protective barrier to the passage of Cry1Ac and plays a protective role against the toxin. However, treatment of T. ni larvae with Calcofluor significantly reduced the larval susceptibility to Cry1Ac. The level of mortality reduction by treatment with Calcofluor was more significant in the resistant T. ni strains than in the susceptible strain. The mechanism for the decrease of susceptibility to Cry1Ac in T. ni treated with Calcofluor needs to be understood. It may result from binding of the toxin to the over expressed PM proteins, preventing the Cry1Ac from reaching the midgut receptor for the toxin or from potential binding of Calcofluor to the midgut receptor for Cry1Ac, leading to inhibition of the toxicity of Cry1Ac in larvae.
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Affiliation(s)
- Wei Guo
- Department of Entomology, Cornell University, Geneva, NY 14456, USA
| | - Wendy Kain
- Department of Entomology, Cornell University, Geneva, NY 14456, USA
| | - Ping Wang
- Department of Entomology, Cornell University, Geneva, NY 14456, USA.
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Liu L, Schepers E, Lum A, Rice J, Yalpani N, Gerber R, Jiménez-Juárez N, Haile F, Pascual A, Barry J, Qi X, Kassa A, Heckert MJ, Xie W, Ding C, Oral J, Nguyen M, Le J, Procyk L, Diehn SH, Crane VC, Damude H, Pilcher C, Booth R, Liu L, Zhu G, Nowatzki TM, Nelson ME, Lu AL, Wu G. Identification and Evaluations of Novel Insecticidal Proteins from Plants of the Class Polypodiopsida for Crop Protection against Key Lepidopteran Pests. Toxins (Basel) 2019; 11:E383. [PMID: 31266212 PMCID: PMC6669613 DOI: 10.3390/toxins11070383] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Revised: 06/21/2019] [Accepted: 06/22/2019] [Indexed: 12/12/2022] Open
Abstract
Various lepidopteran insects are responsible for major crop losses worldwide. Although crop plant varieties developed to express Bacillus thuringiensis (Bt) proteins are effective at controlling damage from key lepidopteran pests, some insect populations have evolved to be insensitive to certain Bt proteins. Here, we report the discovery of a family of homologous proteins, two of which we have designated IPD083Aa and IPD083Cb, which are from Adiantum spp. Both proteins share no known peptide domains, sequence motifs, or signatures with other proteins. Transgenic soybean or corn plants expressing either IPD083Aa or IPD083Cb, respectively, show protection from feeding damage by several key pests under field conditions. The results from comparative studies with major Bt proteins currently deployed in transgenic crops indicate that the IPD083 proteins function by binding to different target sites. These results indicate that IPD083Aa and IPD083Cb can serve as alternatives to traditional Bt-based insect control traits with potential to counter insect resistance to Bt proteins.
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Affiliation(s)
- Lu Liu
- Corteva Agriscience, Hayward, CA 94545, USA
| | | | - Amy Lum
- Corteva Agriscience, Hayward, CA 94545, USA
| | - Janet Rice
- Corteva Agriscience, Johnston, IA 50131, USA
| | | | - Ryan Gerber
- Corteva Agriscience, Johnston, IA 50131, USA
| | | | - Fikru Haile
- Corteva Agriscience, Johnston, IA 50131, USA
| | | | | | - Xiuli Qi
- Corteva Agriscience, Johnston, IA 50131, USA
| | - Adane Kassa
- Corteva Agriscience, Johnston, IA 50131, USA
| | | | | | | | | | | | - James Le
- Corteva Agriscience, Hayward, CA 94545, USA
| | - Lisa Procyk
- Corteva Agriscience, Johnston, IA 50131, USA
| | | | | | | | | | - Russ Booth
- Corteva Agriscience, Johnston, IA 50131, USA
| | - Lu Liu
- Corteva Agriscience, Johnston, IA 50131, USA
| | - Genhai Zhu
- Corteva Agriscience, Hayward, CA 94545, USA
| | | | | | - Albert L Lu
- Corteva Agriscience, Johnston, IA 50131, USA
| | - Gusui Wu
- Corteva Agriscience, Hayward, CA 94545, USA
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Interaction between Insects, Toxins, and Bacteria: Have We Been Wrong So Far? Toxins (Basel) 2018; 10:toxins10070281. [PMID: 29986377 PMCID: PMC6070883 DOI: 10.3390/toxins10070281] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Revised: 07/01/2018] [Accepted: 07/02/2018] [Indexed: 12/19/2022] Open
Abstract
Toxins are a major virulence factor produced by many pathogenic bacteria. In vertebrates, the response of hosts to the bacteria is inseparable from the response to the toxins, allowing a comprehensive understanding of this tripartite host-pathogen-toxin interaction. However, in invertebrates, this interaction has been investigated by two complementary but historically distinct fields of research: toxinology and immunology. In this article, I highlight how such dichotomy between these two fields led to a biased, or even erroneous view of the ecology and evolution of the interaction between insects, toxins, and bacteria. I focus on the reason behind such a dichotomy, on how to bridge the fields together, and on confounding effects that could bias the outcome of the experiments. Finally, I raise four questions at the border of the two fields on the cross-effects between toxins, bacteria, and spores that have been largely underexplored to promote a more comprehensive view of this interaction.
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8
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Tetreau G, Wang R, Wang P. Fitness of Bt-resistant cabbage loopers on Bt cotton plants. PLANT BIOTECHNOLOGY JOURNAL 2017; 15:1322-1330. [PMID: 28273400 PMCID: PMC5595710 DOI: 10.1111/pbi.12718] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Revised: 02/22/2017] [Accepted: 03/01/2017] [Indexed: 06/01/2023]
Abstract
Development of resistance to the insecticidal toxins from Bacillus thuringiensis (Bt) in insects is the major threat to the continued success of transgenic Bt crops in agriculture. The fitness of Bt-resistant insects on Bt and non-Bt plants is a key parameter that determines the development of Bt resistance in insect populations. In this study, a comprehensive analysis of the fitness of Bt-resistant Trichoplusia ni strains on Bt cotton leaves was conducted. The Bt-resistant T. ni strains carried two genetically independent mechanisms of resistance to Bt toxins Cry1Ac and Cry2Ab. The effects of the two resistance mechanisms, individually and in combination, on the fitness of the T. ni strains on conventional non-Bt cotton and on transgenic Bt cotton leaves expressing a single-toxin Cry1Ac (Bollgard I) or two Bt toxins Cry1Ac and Cry2Ab (Bollgard II) were examined. The presence of Bt toxins in plants reduced the fitness of resistant insects, indicated by decreased net reproductive rate (R0 ) and intrinsic rate of increase (r). The reduction in fitness in resistant T. ni on Bollgard II leaves was greater than that on Bollgard I leaves. A 12.4-day asynchrony of adult emergence between the susceptible T. ni grown on non-Bt cotton leaves and the dual-toxin-resistant T. ni on Bollgard II leaves was observed. Therefore, multitoxin Bt plants not only reduce the probability for T. ni to develop resistance but also strongly reduce the fitness of resistant insects feeding on the plants.
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Affiliation(s)
- Guillaume Tetreau
- Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY, USA
| | - Ran Wang
- Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY, USA
- Department of Entomology, Nanjing Agricultural University, Nanjing, China
| | - Ping Wang
- Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY, USA
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Li J, Ma Y, Yuan W, Xiao Y, Liu C, Wang J, Peng J, Peng R, Soberón M, Bravo A, Yang Y, Liu K. FOXA transcriptional factor modulates insect susceptibility to Bacillus thuringiensis Cry1Ac toxin by regulating the expression of toxin-receptor ABCC2 and ABCC3 genes. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2017; 88:1-11. [PMID: 28736301 DOI: 10.1016/j.ibmb.2017.07.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Accepted: 07/19/2017] [Indexed: 06/07/2023]
Abstract
Cry toxins produced by Bacillus thuringiensis (Bt) are insecticidal proteins widely used in insect control. Recently, it was shown that ATP-binding cassette transporter proteins (ABC) such as ABCC2, ABCC3, ABCG1 and ABCA2 are implicated in the insecticidal action of Cry toxins as putative receptors. However, the transcriptional regulators involved in the expression of ABC transporter genes remain unknown. Sequence analysis of promoter regions of ABCC2 gene from Helicoverpa armigera and ABCC3 gene from Spodoptera litura Sl-HP cultured cells, revealed the potential participation of Forkhead box protein A (FOXA), a transcription factor that regulates the expression of genes through remodeling chromatin. To determine if FOXA was involved in regulating expression of ABCC2 and ABCC3 genes, the expression of FOXA, ABCC2 and ABCC3 was compared in Sl-HP cells that are sensitive to Cry1Ac toxin with those in S. frugiperda Sf9 cells that are not sensitive to the toxin. Expression levels of those genes were significantly higher in Sl-HP than in Sf9 cells. Transient expression of FOXA in Sf9 cells activated ABCC2 and ABCC3 transcription, which directly correlated with enhanced Cry1Ac-susceptibility in these cells. Silencing of FOXA gene expression by RNAi in H. armigera larvae resulted in a decreased expression of ABCC2 and ABCC3 without affecting expression of other Cry toxin receptor genes such as alkaline phosphatase, aminopeptidase or cadherin. Silencing of FOXA gene expression also resulted in a Cry1Ac-tolerant phenotype since lower mortality and higher pupation rate were observed in diet containing Cry1Ac protoxin in comparison with the control group. These results demonstrate that FOXA up-regulates expression of the Cry1Ac-toxin receptor ABCC2 and ABCC3 genes, and that lower FOXA expression correlates with tolerance to Cry toxin in cell lines and in lepidopteran larvae.
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Affiliation(s)
- Jianghuai Li
- Institute of Entomology, School of Life Sciences, Central China Normal University, Wuhan 430079, China
| | - Yuemin Ma
- Institute of Entomology, School of Life Sciences, Central China Normal University, Wuhan 430079, China
| | - Wanli Yuan
- Institute of Entomology, School of Life Sciences, Central China Normal University, Wuhan 430079, China
| | - Yutao Xiao
- Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen 518120, China
| | - Chenxi Liu
- State Key Laboratory for Biology of Plant Disease and Insect Pests, Chinese Academy of Agricultural Sciences, West Yuanmingyuan Road, Beijing 100193, China
| | - Jia Wang
- Institute of Entomology, School of Life Sciences, Central China Normal University, Wuhan 430079, China
| | - Jianxin Peng
- Institute of Entomology, School of Life Sciences, Central China Normal University, Wuhan 430079, China
| | - Rong Peng
- Institute of Entomology, School of Life Sciences, Central China Normal University, Wuhan 430079, China
| | - Mario Soberón
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca 62250, Morelos, Mexico
| | - Alejandra Bravo
- Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca 62250, Morelos, Mexico.
| | - Yongbo Yang
- Institute of Entomology, School of Life Sciences, Central China Normal University, Wuhan 430079, China.
| | - Kaiyu Liu
- Institute of Entomology, School of Life Sciences, Central China Normal University, Wuhan 430079, China.
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10
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Wang R, Tetreau G, Wang P. Effect of crop plants on fitness costs associated with resistance to Bacillus thuringiensis toxins Cry1Ac and Cry2Ab in cabbage loopers. Sci Rep 2016; 6:20959. [PMID: 26868936 PMCID: PMC4751490 DOI: 10.1038/srep20959] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Accepted: 01/13/2016] [Indexed: 01/01/2023] Open
Abstract
Fitness costs associated with resistance to Bacillus thuringiensis (Bt) toxins critically impact the development of resistance in insect populations. In this study, the fitness costs in Trichoplusia ni strains associated with two genetically independent resistance mechanisms to Bt toxins Cry1Ac and Cry2Ab, individually and in combination, on four crop plants (cabbage, cotton, tobacco and tomato) were analyzed, in comparison with their near-isogenic susceptible strain. The net reproductive rate (R0) and intrinsic rate of increase (r) of the T. ni strains, regardless of their resistance traits, were strongly affected by the host plants. The ABCC2 gene-linked mechanism of Cry1Ac resistance was associated with relatively low fitness costs, while the Cry2Ab resistance mechanism was associated with higher fitness costs. The fitness costs in the presence of both resistance mechanisms in T. ni appeared to be non-additive. The relative fitness of Bt-resistant T. ni depended on the specific resistance mechanisms as well as host plants. In addition to difference in survivorship and fecundity, an asynchrony of adult emergence was observed among T. ni with different resistance mechanisms and on different host plants. Therefore, mechanisms of resistance and host plants available in the field are both important factors affecting development of Bt resistance in insects.
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Affiliation(s)
- Ran Wang
- Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY 14456, USA.,Department of Entomology, Nanjing Agricultural University, Nanjing 210095, China
| | - Guillaume Tetreau
- Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY 14456, USA
| | - Ping Wang
- Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY 14456, USA
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11
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Fabrick JA, Unnithan GC, Yelich AJ, DeGain B, Masson L, Zhang J, Carrière Y, Tabashnik BE. Multi-Toxin Resistance Enables Pink Bollworm Survival on Pyramided Bt Cotton. Sci Rep 2015; 5:16554. [PMID: 26559899 PMCID: PMC5156061 DOI: 10.1038/srep16554] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Accepted: 10/15/2015] [Indexed: 11/09/2022] Open
Abstract
Transgenic crops producing Bacillus thuringiensis (Bt) proteins kill key insect pests, providing economic and environmental benefits. However, the evolution of pest resistance threatens the continued success of such Bt crops. To delay or counter resistance, transgenic plant "pyramids" producing two or more Bt proteins that kill the same pest have been adopted extensively. Field populations of the pink bollworm (Pectinophora gossypiella) in the United States have remained susceptible to Bt toxins Cry1Ac and Cry2Ab, but field-evolved practical resistance to Bt cotton producing Cry1Ac has occurred widely in India. Here we used two rounds of laboratory selection to achieve 18,000- to 150,000-fold resistance to Cry2Ab in pink bollworm. Inheritance of resistance to Cry2Ab was recessive, autosomal, conferred primarily by one locus, and independent of Cry1Ac resistance. We created a strain with high resistance to both toxins by crossing the Cry2Ab-resistant strain with a Cry1Ac-resistant strain, followed by one selection with Cry2Ab. This multi-toxin resistant strain survived on field-collected Bt cotton bolls producing both toxins. The results here demonstrate the risk of evolution of resistance to pyramided Bt plants, particularly when toxins are deployed sequentially and refuges are scarce, as seen with Bt cotton and pink bollworm in India.
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Affiliation(s)
- Jeffrey A Fabrick
- USDA ARS, U.S. Arid Land Agricultural Research Center, Maricopa, AZ 85138 USA
| | | | - Alex J Yelich
- Department of Entomology, University of Arizona, Tucson, AZ 85721 USA
| | - Ben DeGain
- Department of Entomology, University of Arizona, Tucson, AZ 85721 USA
| | - Luke Masson
- Biotechnology Research Institute, National Research Council of Canada, Montreal, QC, Canada H4P 2R2
| | - Jie Zhang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, Haidian District, 100193 Peoples Republic of China
| | - Yves Carrière
- Department of Entomology, University of Arizona, Tucson, AZ 85721 USA
| | - Bruce E Tabashnik
- Department of Entomology, University of Arizona, Tucson, AZ 85721 USA
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12
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Cross-resistance to toxins used in pyramided Bt crops and resistance to Bt sprays in Helicoverpa zea. J Invertebr Pathol 2015; 132:149-156. [DOI: 10.1016/j.jip.2015.10.003] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Revised: 09/28/2015] [Accepted: 10/08/2015] [Indexed: 12/29/2022]
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13
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Resistance to Bacillus thuringiensis Toxin Cry2Ab in Trichoplusia ni Is Conferred by a Novel Genetic Mechanism. Appl Environ Microbiol 2015; 81:5184-95. [PMID: 26025894 DOI: 10.1128/aem.00593-15] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Accepted: 05/18/2015] [Indexed: 01/06/2023] Open
Abstract
The resistance to the Bacillus thuringiensis (Bt) toxin Cry2Ab in a greenhouse-originated Trichoplusia ni strain resistant to both Bt toxins Cry1Ac and Cry2Ab was characterized. Biological assays determined that the Cry2Ab resistance in the T. ni strain was a monogenic recessive trait independent of Cry1Ac resistance, and there existed no significant cross-resistance between Cry1Ac and Cry2Ab in T. ni. From the dual-toxin-resistant T. ni strain, a strain resistant to Cry2Ab only was isolated, and the Cry2Ab resistance trait was introgressed into a susceptible laboratory strain to facilitate comparative analysis of the Cry2Ab resistance with the susceptible T. ni strain. Results from biochemical analysis showed no significant difference between the Cry2Ab-resistant and -susceptible T. ni larvae in midgut proteases, including caseinolytic proteolytic activity and zymogram profile and serine protease activities, in midgut aminopeptidase and alkaline phosphatase activity, and in midgut esterases and hemolymph plasma melanization activity. For analysis of genetic linkage of Cry2Ab resistance with potential Cry toxin receptor genes, molecular markers for the midgut cadherin, alkaline phosphatase (ALP), and aminopeptidase N (APN) genes were identified between the original greenhouse-derived dual-toxin-resistant and the susceptible laboratory T. ni strains. Genetic linkage analysis showed that the Cry2Ab resistance in T. ni was not genetically associated with the midgut genes coding for the cadherin, ALP, and 6 APNs (APN1 to APN6) nor associated with the ABC transporter gene ABCC2. Therefore, the Cry2Ab resistance in T. ni is conferred by a novel but unknown genetic mechanism.
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