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Bruce E Tabashnik - One of the best experts on this subject based on the ideXlab platform.
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binding of Bacillus Thuringiensis Toxin cry1ac to multiple sites of cadherin in pink bollworm
Insect Biochemistry and Molecular Biology, 2007Co-Authors: Jeffrey A Fabrick, Bruce E TabashnikAbstract:Abstract Toxins from Bacillus Thuringiensis (Bt) are widely used for pest control. In particular, Bt Toxin Cry1Ac produced by transgenic cotton kills some key lepidopteran pests. We found that Cry1Ac binds to recombinant peptides corresponding to extracellular regions of a cadherin protein (BtR) in a major cotton pest, pink bollworm ( Pectinophora gossypiella ) (PBW). In conjunction with previous results showing that PBW resistance to Cry1Ac is linked with mutations in the BtR gene, the results reported here support the hypothesis that BtR is a receptor for Cry1Ac in PBW. Similar to other lepidopteran cadherins that bind Bt Toxins, BtR has at least two Cry1Ac-binding domains in cadherin-repeat regions 10 and 11, which are immediately adjacent to the membrane proximal region. However, unlike cadherins from Manduca sexta and Bombyx mori , Toxin binding was not seen in regions more distal from the membrane proximal region. We also found that both the proToxin and activated Toxin forms of Cry1Ac bound to recombinant BtR fragments, suggesting that Cry1Ac activation may occur either before or after receptor binding.
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Inheritance of resistance to the Cry1Ab Bacillus Thuringiensis Toxin in Ostrinia nubilalis (Lepidoptera: Crambidae).
Journal of economic entomology, 2006Co-Authors: Analiza P. Alves, Bruce E Tabashnik, Terrence A Spencer, Blair D SiegfriedAbstract:Abstract Laboratory selection with Cry1Ab, the predominant Bacillus Thuringiensis (Bt) Toxin in transgenic corn, Zea mays L., produced >1000-fold resistance in two laboratory strains of European corn borer, Ostrinia nubilalis (Hubner). We tested the offspring of various crosses to determine the mode of inheritance of resistance to Cry1Ab. Patterns of inheritance of resistance were similar in the two resistant strains. The progeny of reciprocal F1 crosses (resistant male × susceptible female and vice versa) responded alike in bioassays, indicating autosomal inheritance. The median lethal concentrations (LC50 values) of F1 were intermediate between the resistant and susceptible parents, indicating approximately additive inheritance. However, the dominance of resistance increased as the concentration of Cry1Ab decreased. Analysis of progeny from backcrosses (F1 × susceptible strain) suggests that resistance was controlled by more than one locus. In particular, the fit of observed to expected mortality improv...
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Contamination of refuges by Bacillus Thuringiensis Toxin genes from transgenic maize
Proceedings of the National Academy of Sciences of the United States of America, 2004Co-Authors: Charles F. Chilcutt, Bruce E TabashnikAbstract:Transgenic crops producing insecticidal Toxins from Bacillus Thuringiensis (Bt) are widely used to control pests, but their benefits will be lost if pests evolve resistance. The mandated high-dose/refuge strategy for delaying pest resistance requires planting refuges of Toxin-free crops near Bt crops to promote survival of susceptible pests. We report that pollen-mediated gene flow up to 31 m from Bt maize caused low to moderate Bt Toxin levels in kernels of non-Bt maize refuge plants. Immunoassays of non-Bt maize sampled from the field showed that the mean concentration of Bt Toxin Cry1Ab in kernels and the percentage of kernels with Cry1Ab decreased with distance from Bt maize. The highest Bt Toxin concentration in pooled kernels of non-Bt maize plants was 45% of the mean concentration in kernels from adjacent Bt maize plants. Most previous work on gene flow from transgenic crops has emphasized potential effects of transgene movement on wild relatives of crops, landraces, and organic plantings, whereas implications for pest resistance have been largely ignored. Variable Bt Toxin production in seeds of refuge plants undermines the high-dose/refuge strategy and could accelerate pest resistance to Bt crops. Thus, guidelines should be revised to reduce gene flow between Bt crops and refuge plants.
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control of resistant pink bollworm pectinophora gossypiella by transgenic cotton that produces Bacillus Thuringiensis Toxin cry2ab
Applied and Environmental Microbiology, 2002Co-Authors: Bruce E Tabashnik, Timothy J. Dennehy, Maria A Sims, Karen Larkin, Graham P Head, William J Moar, Yves CarriereAbstract:Crops genetically engineered to produce Bacillus Thuringiensis Toxins for insect control can reduce use of conventional insecticides, but insect resistance could limit the success of this technology. The first generation of transgenic cotton with B. Thuringiensis produces a single Toxin, Cry1Ac, that is highly effective against susceptible larvae of pink bollworm (Pectinophora gossypiella), a major cotton pest. To counter potential problems with resistance, second-generation transgenic cotton that produces B. Thuringiensis Toxin Cry2Ab alone or in combination with Cry1Ac has been developed. In greenhouse bioassays, a pink bollworm strain selected in the laboratory for resistance to Cry1Ac survived equally well on transgenic cotton with Cry1Ac and on cotton without Cry1Ac. In contrast, Cry1Ac-resistant pink bollworm had little or no survival on secondgeneration transgenic cotton with Cry2Ab alone or with Cry1Ac plus Cry2Ab. Artificial diet bioassays showed that resistance to Cry1Ac did not confer strong cross-resistance to Cry2Aa. Strains with >90% larval survival on diet with 10 g of Cry1Ac per ml showed 0% survival on diet with 3.2 or 10 g of Cry2Aa per ml. However, the average survival of larvae fed a diet with 1 g of Cry2Aa per ml was higher for Cry1Ac-resistant strains (2 to 10%) than for susceptible strains (0%). If plants with Cry1Ac plus Cry2Ab are deployed while genes that confer resistance to each of these Toxins are rare, and if the inheritance of resistance to both Toxins is recessive, the efficacy of transgenic cotton might be greatly extended.
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Cross-Resistance and Stability of Resistance to Bacillus Thuringiensis Toxin Cry1C in Diamondback Moth
Applied and environmental microbiology, 2001Co-Authors: Yong Biao Liu, Bruce E Tabashnik, Susan K Meyer, Neil CrickmoreAbstract:We tested Toxins of Bacillus Thuringiensis against larvae from susceptible, Cry1C-resistant, and Cry1A-resistant strains of diamondback moth (Plutella xylostella). The Cry1C-resistant strain, which was derived from a field population that had evolved resistance to B. Thuringiensis subsp. kurstaki and B. Thuringiensis subsp. aizawai, was selected repeatedly with Cry1C in the laboratory. The Cry1C-resistant strain had strong cross-resistance to Cry1Ab, Cry1Ac, and Cry1F, low to moderate cross-resistance to Cry1Aa and Cry9Ca, and no cross-resistance to Cry1Bb, Cry1Ja, and Cry2A. Resistance to Cry1C declined when selection was relaxed. Together with previously reported data, the new data on the cross-resistance of a Cry1C-resistant strain reported here suggest that resistance to Cry1A and Cry1C Toxins confers little or no cross-resistance to Cry1Bb, Cry2Aa, or Cry9Ca. Therefore, these Toxins might be useful in rotations or combinations with Cry1A and Cry1C Toxins. Cry9Ca was much more potent than Cry1Bb or Cry2Aa and thus might be especially useful against diamondback moth.
Ping Wang - One of the best experts on this subject based on the ideXlab platform.
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resistance to Bacillus Thuringiensis Toxin cry2ab in trichoplusia ni is conferred by a novel genetic mechanism
Applied and Environmental Microbiology, 2015Co-Authors: Xiaozhao Song, Wendy Kain, Douglas Cassidy, Ping WangAbstract: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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resistance of trichoplusia ni to Bacillus Thuringiensis Toxin cry1ac is independent of alteration of the cadherin like receptor for cry Toxins
PLOS ONE, 2012Co-Authors: Xin Zhang, Wendy Kain, Kasorn Tiewsiri, Lihua Huang, Ping WangAbstract:Alteration of binding sites for Bacillus Thuringiensis (Bt) Toxins in insect midgut is the major mechanism of high-level resistance to Bt Toxins in insects. The midgut cadherin is known to be a major binding protein for Bt Cry1A Toxins and linkage of Bt-resistance to cadherin gene mutations has been identified in lepidopterans. The resistance to Bt Toxin Cry1Ac evolved in greenhouse populations of Trichoplusia ni has been identified to be associated with the down-regulation of an aminopeptidase N (APN1) gene by a trans-regulatory mechanism and the resistance gene has been mapped to the locus of an ABC transporter (ABCC2) gene. However, whether cadherin is also involved with Cry1Ac-resistance in T. ni requires to be understood. Here we report that the Cry1Ac-resistance in T. ni is independent of alteration of the cadherin. The T. ni cadherin cDNA was cloned and the cadherin sequence showed characteristic features known to cadherins from Lepidoptera. Various T. ni cadherin gene alleles were identified and genetic linkage analysis of the cadherin alleles with Cry1Ac-resistance showed no association of the cadherin gene with the Cry1Ac-resistance in T. ni. Analysis of cadherin transcripts showed no quantitative difference between the susceptible and Cry1Ac-resistant T. ni larvae. Quantitative proteomic analysis of midgut BBMV proteins by iTRAQ-2D-LC-MS/MS determined that there was no quantitative difference in cadherin content between the susceptible and the resistant larvae and the cadherin only accounted for 0.0014% (mol%) of the midgut BBMV proteins, which is 1/300 of APN1 in molar ratio. The cadherin from both the susceptible and resistant larvae showed as a 200-kDa Cry1Ac-binding protein by Toxin overlay binding analysis, and nano-LC-MS/MS analysis of the 200-kDa cadherin determined that there is no quantitative difference between the susceptible and resistant larvae. Results from this study indicate that the Cry1Ac-resistance in T. ni is independent of cadherin alteration.
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differential alteration of two aminopeptidases n associated with resistance to Bacillus Thuringiensis Toxin cry1ac in cabbage looper
Proceedings of the National Academy of Sciences of the United States of America, 2011Co-Authors: Kasorn Tiewsiri, Ping WangAbstract:The soil bacterium Bacillus Thuringiensis (Bt) is the most successfully used biopesticide in agriculture, and its insecticidal protein genes are the primary transgenes used for insect control in transgenic crops. However, evolution of insect resistance to Bt Toxins threatens the long-term future of Bt applications. To date, cases of resistance to Bt Toxins have been reported in agricultural situations in six insect species, but the molecular basis for these cases of resistance remains unclear. Here we report that the resistance to the Bt Toxin Cry1Ac in the cabbage looper, Trichoplusia ni, evolved in greenhouses, is associated with differential alteration of two midgut aminopeptidases N, APN1 and APN6, conferred by a trans-regulatory mechanism. Biochemical, proteomic, and molecular analyses showed that in the Cry1Ac-resistant T. ni, APN1 was significantly down-regulated, whereas APN6 was significantly up-regulated. The Cry1Ac resistance was correlated with down-regulation of APN1 but not with the up-regulation of APN6. The concurrent up-regulation of APN6 and down-regulation of APN1 might play a role in compensating for the loss of APN1 to minimize the fitness costs of the resistance. Along with identifying reduced expression of APN1 as the molecular basis of Bt resistance selected in an agricultural setting, our findings demonstrate the importance of APN1 to the mode of action of Bt Toxin Cry1Ac.
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Parallel Evolution of Bacillus Thuringiensis Toxin Resistance in Lepidoptera
Genetics, 2011Co-Authors: Simon W. Baxter, David G Heckel, Neil Crickmore, Francisco Rubén Badenes-pérez, Anna Morrison, Heiko Vogel, Wendy Kain, Ping Wang, Chris D. JigginsAbstract:Despite the prominent and worldwide use of Bacillus Thuringiensis (Bt) insecticidal Toxins in agriculture, knowledge of the mechanism by which they kill pests remains incomplete. Here we report genetic mapping of a membrane transporter (ABCC2) to a locus controlling Bt Cry1Ac Toxin resistance in two lepidopterans, implying that this protein plays a critical role in Bt function.
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mechanism of resistance to Bacillus Thuringiensis Toxin cry1ac in a greenhouse population of the cabbage looper trichoplusia ni
Applied and Environmental Microbiology, 2007Co-Authors: Ping Wang, Anthony M. Shelton, Wendy Kain, Juan Ferré, Jianzhou Zhao, Ana Rodrigosimon, Alida F Janmaat, Judith H MyersAbstract:The cabbage looper, Trichoplusia ni, is one of only two insect species that have evolved resistance to Bacillus Thuringiensis in agricultural situations. The trait of resistance to B. Thuringiensis Toxin Cry1Ac from a greenhouse-evolved resistant population of T. ni was introgressed into a highly inbred susceptible laboratory strain. The resulting introgression strain, GLEN-Cry1Ac-BCS, and its nearly isogenic susceptible strain were subjected to comparative genetic and biochemical studies to determine the mechanism of resistance. Results showed that midgut proteases, hemolymph melanization activity, and midgut esterase were not altered in the GLEN-Cry1Ac-BCS strain. The pattern of cross-resistance of the GLEN-Cry1Ac-BCS strain to 11 B. Thuringiensis Cry Toxins showed a correlation of the resistance with the Cry1Ab/Cry1Ac binding site in T. ni. This cross-resistance pattern is different from that found in a previously reported laboratory-selected Cry1Ab-resistant T. ni strain, evidently indicating that the greenhouse-evolved resistance involves a mechanism different from the laboratory-selected resistance. Determination of specific binding of B. Thuringiensis Toxins Cry1Ab and Cry1Ac to the midgut brush border membranes confirmed the loss of midgut binding to Cry1Ab and Cry1Ac in the resistant larvae. The loss of midgut binding to Cry1Ab/Cry1Ac is inherited as a recessive trait, which is consistent with the recessive inheritance of Cry1Ab/Cry1Ac resistance in this greenhouse-derived T. ni population. Therefore, it is concluded that the mechanism for the greenhouse-evolved Cry1Ac resistance in T. ni is an alteration affecting the binding of Cry1Ab and Cry1Ac to the Cry1Ab/Cry1Ac binding site in the midgut.
Yihua Yang - One of the best experts on this subject based on the ideXlab platform.
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resistance to Bacillus Thuringiensis Toxin cry2ab and survival on single Toxin and pyramided cotton in cotton bollworm from china
Evolutionary Applications, 2017Co-Authors: Song Yang, Yves Carriere, Yidong Wu, Yihua YangAbstract:Ministry of Agriculture of China [2016ZX08011002-005]; National Natural Science Foundation of China [31272064]; US Department of Agriculture Biotechnology Risk Assessment Grant Award [2014-33522-22214]
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Characterization of resistance to Bacillus Thuringiensis Toxin Cry1Ac in Plutella xylostella from China
Journal of invertebrate pathology, 2010Co-Authors: Youjing Gong, Chongli Wang, Yihua YangAbstract:Abstract A field population (SZ) of Plutella xylostella, collected from the cabbage field in Shenzhen, Guangdong Province of China in 2002, showed 2.3-fold resistance to Cry1Aa, 110-fold to Cry1Ab, 30-fold to Cry1Ac, 2.1-fold to Cry1F, 5.3-fold to Cry2Aa and 6-fold resistance to Bacillus Thuringiensis var. kurstaki (Btk) compared with a susceptible strain (ROTH). The SZBT strain was derived from the SZ population through 20 generations of selection with activated Cry1Ac in the laboratory. While the SZBT strain developed 1200-fold resistance to Cry1Ac after selection, resistance to Cry1Aa, Cry1Ab, Cry1F, and Btk increased to 31-, 1900-,>33- and 17-fold compared with the ROTH strain. However, little or no cross-resistance was detected to Cry1B, Cry1C and Cry2Aa in the SZBT strain. Genetic cross analyses between the SZBT and ROTH strains revealed that Cry1Ac-resistance in the SZBT strain was controlled by a single, autosomal, incompletely recessive gene. Binding studies with 125I-labeled Cry1Ac showed that the brush border membrane vesicles (BBMVs) of midguts from the resistant SZBT insects had lost binding to Cry1Ac. Allelic complementation tests demonstrated that the major Bt resistance locus in the SZBT strain was same as that in the Cry1Ac-R strain which has “mode 1” resistance to Bt. An F1 screen of 120 single-pair families between the SZBT strain and three field populations collected in 2008 was carried out. Based on this approach, the estimated frequencies of Cry1Ac-resistance alleles were 0.156 in the Yuxi population from Yunnan province, and 0.375 and 0.472 respectively in the Guangzhou and Huizhou populations from Guangdong province.
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diverse cadherin mutations conferring resistance to Bacillus Thuringiensis Toxin cry1ac in helicoverpa armigera
Insect Biochemistry and Molecular Biology, 2010Co-Authors: Jing Zhao, Lin Jin, Yihua YangAbstract:Transgenic cotton expressing Bacillus Thuringiensis (Bt) Toxins has been widely adopted to control some key lepidopteran pests including the bollworm Helicoverpa armigera. Evolution of resistance to Bt cotton by target pests is a major threat to the continued success of Bt cotton. Previous results revealed 3 null alleles (r1-r3) of a cadherin gene (Ha_BtR) conferring Cry1Ac resistance in H. armigera. An F(1) screen of 123 single-pair families was conducted between a Cry1Ac-resistant strain (the SCD-r1 strain, homozygous for the r1 allele of Ha_BtR) and field-derived insects from Jiangpu population (Jiangsu province, China) in 2008. Five new null alleles of Ha_BtR (r4-r8) were identified in six candidate single-pair families. These null alleles were created through either an insertion or a point mutation. Interestingly, intact alleles of Ha_BtR were found in two field-derived insects from another two candidate single-pair families. It suggests that these two field-derived insects may carry novel resistance alleles of Ha_BtR, with missense mutations resulting in a non-functional cadherin protein, or a major dominant mutation at a locus other than cadherin. The resistance allele frequency of Ha_BtR was detected at an appreciable level (0.024) in the Jiangpu population of H. armigera in 2008. Together with previous findings, a total of eight different resistance alleles of Ha_BtR were identified from three Chinese strains of H. armigera. Mutational diversity of Ha_BtR could impair DNA screening for Bt resistance allele frequency in the field, and an F(1) screen should be used routinely for monitoring cadherin-based resistance allele frequencies in H. armigera.
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Introgression of a disrupted cadherin gene enables susceptible Helicoverpa armigera to obtain resistance to Bacillus Thuringiensis Toxin Cry1Ac
Bulletin of entomological research, 2008Co-Authors: Yuanhong Yang, Yihua Yang, W.-y. Gao, Jinjin GuoAbstract:A disrupted allele (r1) of a cadherin gene (Ha_BtR) is genetically associated with incompletely recessive resistance to Bacillus Thuringiensis Toxin Cry1Ac in a Cry1Ac-selected strain (GYBT) of Helicoverpa armigera. The r1 allele of Ha_BtR was introgressed into a susceptible SCD strain by crossing the GYBT strain to the SCD strain, followed by repeated backcrossing to the SCD strain and molecular marker assisted family selection. The introgressed strain (designated as SCD-r1, carrying homozygous r1 allele) obtained 438-fold resistance to Cry1Ac, >41-fold resistance to Cry1Aa and 31-fold resistance Cry1Ab compared with the SCD strain; however, there was no significant difference in susceptibility to Cry2Aa between the integrated and parent strains. It confirms that the loss of function mutation of Ha_BtR alone can confer medium to high levels of resistance to the three Cry1A Toxins in H. armigera. Reciprocal crosses between the SCD and SCD-r1 strains showed that resistance to Cry1Ac in the SCD-r1 strain was completely recessive. Life tables of the SCD and SCD-r1 strains on artificial diet in the laboratory were constructed, and results showed that the net replacement rate (R0) did not differ between the strains. The toxicity of two chemical insecticides, fenvalerate and monocrotophos, against the SCD-r1 strain was not significantly different from that to the SCD strain. However, larval development time of the SCD-r1 strain was significantly longer than that of the SCD strain, indicating a fitness cost of slower larval growth is associated with Ha_BtR disruption in H. armigera.
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mutated cadherin alleles from a field population of helicoverpa armigera confer resistance to Bacillus Thuringiensis Toxin cry1ac
Applied and Environmental Microbiology, 2007Co-Authors: Yajun Yang, Haiyan Chen, Yihua YangAbstract:The global area of cotton (Gossypium hirsutum L.) genetically engineered to produce the Bacillus Thuringiensis Toxin (transgenic Bt cotton) planted in 2006 was 12.1 million hectares (12). Transgenic Bt cotton has been adopted extensively to reduce reliance on insecticides and save labor and costs in many countries. The rapid evolution of resistance by target pests could completely undermine the advantages of this new technology. Despite the expectations of many scientists and the predictions from models, resistance to Bt crops in the field has not yet been reported after a decade of adoption of Bt crops (2, 10, 19). However, we should not underestimate the ability of target insects to adapt to Bt crops, because resistance to Bt crops by target insects remains a question not of “if” but of “when.” Invertebrates have demonstrated a range of resistance mechanisms to B. Thuringiensis Toxins (11). The diamondback moth, Plutella xylostella, has already evolved resistance to Bacillus Thuringiensis subspecies in the field (16, 18). The cotton bollworm Helicoverpa armigera (Hubner) is the most important target pest of transgenic Bt cotton in China, India, Australia, and South Africa. Laboratory selection experiments from several countries demonstrate that this pest has the capacity to evolve resistance to the B. Thuringiensis Toxin Cry1Ac protein contained in Bt cotton (1, 14, 24). Understanding the molecular mechanisms of B. Thuringiensis resistance is critical for developing efficient DNA-based monitoring of the resistance frequency for early resistance warning and is key to informed and proactive resistance management. Mutations in a cadherin gene were identified as the causes for the recessive resistance to Cry1Ac in three major lepidopteran cotton pests, Heliothis virescens, Pectinophora gossypiella, and H. armigera (7, 15, 24). However, the mutant alleles found in laboratory-selected strains may not be identical to those present in field populations (3). In fact, two recent publications reported that no resistance alleles of cadherin of P. gossypiella and H. virescens were detected from field populations after large-scale screening (8, 20). Because the cadherin genes are not essential to the survival of P. gossypiella, H. virescens, and H. armigera (at least under laboratory conditions) (7, 15, 24), any mutation that nullifies the cadherin protein as a key functional receptor could confer Cry1Ac resistance. It is therefore very important to establish whether any such mutant cadherin alleles are present in the field, leading to the development of an appropriate DNA-based resistance surveillance program. As suggested by Yang et al. (26), it is both feasible and necessary to screen for resistance-associated cadherin alleles from field populations of H. armigera by using the single-pair mating technique (or F1 screen). Field-derived moths of H. armigera can be crossed individually with moths from the laboratory-selected GYBT strain (r1r1), which shows recessive resistance to Cry1Ac (24). The mutated cadherin genotype status of field-derived moths will be revealed if their F1 offspring show significant Cry1Ac resistance. Here, we report the isolation of two new cadherin alleles conferring Cry1Ac resistance from a field population of H. armigera by using this strategy. Our results provide an important foundation for a DNA-based detection method for monitoring the frequency of mutant cadherin alleles in field populations of H. armigera.
Sean M Prager - One of the best experts on this subject based on the ideXlab platform.
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spider mite infestations reduce Bacillus Thuringiensis Toxin concentration in corn leaves and predators avoid spider mites that have fed on Bacillus Thuringiensis corn
Annals of Applied Biology, 2014Co-Authors: Sean M Prager, Xavier Martini, H Guvvala, Christian Nansen, J G LundgrenAbstract:Perceived benefits of insecticidal transgenic crops include reduced usage of broad-based insecticides, and therefore lower risk to non-target organisms. Numerous studies have documented low or no direct toxicity of Bacillus Thuringiensis (Bt)-derived Toxins against non-target organisms, but there has been less research on (a) effects of secondary pest infestations on Bt expressing in crops and (b) behavioural responses by predators feeding on host arthropods from Bt crops - both topics are investigated in this study. We quantified predation by the obligate spider mite predator Phytoseiulus persimilis of carmine spider mites (Tetranychus cinnabarinus), reared on Bt or non-Bt corn (Zea mays). Both no-choice and two-choice studies were conducted. In addition, we quantified Toxin levels in corn leaves with/without spider mite infestation. Under no-choice conditions, P. persimilis consumed non-Bt spider mites at a faster rate than Bt spider mites. Under two-choice conditions, P. persimilis spent more time in the vicinity of non-Bt spider mites than near Bt spider mites. Corn infested with spider mites exhibited lower Toxin levels than non-infested plants. These results suggest potentially complex interactions among non-target herbivores, their natural enemies and Bt crops. © 2014 Association of Applied Biologists.
Wendy Kain - One of the best experts on this subject based on the ideXlab platform.
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resistance to Bacillus Thuringiensis Toxin cry2ab in trichoplusia ni is conferred by a novel genetic mechanism
Applied and Environmental Microbiology, 2015Co-Authors: Xiaozhao Song, Wendy Kain, Douglas Cassidy, Ping WangAbstract: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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resistance of trichoplusia ni to Bacillus Thuringiensis Toxin cry1ac is independent of alteration of the cadherin like receptor for cry Toxins
PLOS ONE, 2012Co-Authors: Xin Zhang, Wendy Kain, Kasorn Tiewsiri, Lihua Huang, Ping WangAbstract:Alteration of binding sites for Bacillus Thuringiensis (Bt) Toxins in insect midgut is the major mechanism of high-level resistance to Bt Toxins in insects. The midgut cadherin is known to be a major binding protein for Bt Cry1A Toxins and linkage of Bt-resistance to cadherin gene mutations has been identified in lepidopterans. The resistance to Bt Toxin Cry1Ac evolved in greenhouse populations of Trichoplusia ni has been identified to be associated with the down-regulation of an aminopeptidase N (APN1) gene by a trans-regulatory mechanism and the resistance gene has been mapped to the locus of an ABC transporter (ABCC2) gene. However, whether cadherin is also involved with Cry1Ac-resistance in T. ni requires to be understood. Here we report that the Cry1Ac-resistance in T. ni is independent of alteration of the cadherin. The T. ni cadherin cDNA was cloned and the cadherin sequence showed characteristic features known to cadherins from Lepidoptera. Various T. ni cadherin gene alleles were identified and genetic linkage analysis of the cadherin alleles with Cry1Ac-resistance showed no association of the cadherin gene with the Cry1Ac-resistance in T. ni. Analysis of cadherin transcripts showed no quantitative difference between the susceptible and Cry1Ac-resistant T. ni larvae. Quantitative proteomic analysis of midgut BBMV proteins by iTRAQ-2D-LC-MS/MS determined that there was no quantitative difference in cadherin content between the susceptible and the resistant larvae and the cadherin only accounted for 0.0014% (mol%) of the midgut BBMV proteins, which is 1/300 of APN1 in molar ratio. The cadherin from both the susceptible and resistant larvae showed as a 200-kDa Cry1Ac-binding protein by Toxin overlay binding analysis, and nano-LC-MS/MS analysis of the 200-kDa cadherin determined that there is no quantitative difference between the susceptible and resistant larvae. Results from this study indicate that the Cry1Ac-resistance in T. ni is independent of cadherin alteration.
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Parallel Evolution of Bacillus Thuringiensis Toxin Resistance in Lepidoptera
Genetics, 2011Co-Authors: Simon W. Baxter, David G Heckel, Neil Crickmore, Francisco Rubén Badenes-pérez, Anna Morrison, Heiko Vogel, Wendy Kain, Ping Wang, Chris D. JigginsAbstract:Despite the prominent and worldwide use of Bacillus Thuringiensis (Bt) insecticidal Toxins in agriculture, knowledge of the mechanism by which they kill pests remains incomplete. Here we report genetic mapping of a membrane transporter (ABCC2) to a locus controlling Bt Cry1Ac Toxin resistance in two lepidopterans, implying that this protein plays a critical role in Bt function.
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mechanism of resistance to Bacillus Thuringiensis Toxin cry1ac in a greenhouse population of the cabbage looper trichoplusia ni
Applied and Environmental Microbiology, 2007Co-Authors: Ping Wang, Anthony M. Shelton, Wendy Kain, Juan Ferré, Jianzhou Zhao, Ana Rodrigosimon, Alida F Janmaat, Judith H MyersAbstract:The cabbage looper, Trichoplusia ni, is one of only two insect species that have evolved resistance to Bacillus Thuringiensis in agricultural situations. The trait of resistance to B. Thuringiensis Toxin Cry1Ac from a greenhouse-evolved resistant population of T. ni was introgressed into a highly inbred susceptible laboratory strain. The resulting introgression strain, GLEN-Cry1Ac-BCS, and its nearly isogenic susceptible strain were subjected to comparative genetic and biochemical studies to determine the mechanism of resistance. Results showed that midgut proteases, hemolymph melanization activity, and midgut esterase were not altered in the GLEN-Cry1Ac-BCS strain. The pattern of cross-resistance of the GLEN-Cry1Ac-BCS strain to 11 B. Thuringiensis Cry Toxins showed a correlation of the resistance with the Cry1Ab/Cry1Ac binding site in T. ni. This cross-resistance pattern is different from that found in a previously reported laboratory-selected Cry1Ab-resistant T. ni strain, evidently indicating that the greenhouse-evolved resistance involves a mechanism different from the laboratory-selected resistance. Determination of specific binding of B. Thuringiensis Toxins Cry1Ab and Cry1Ac to the midgut brush border membranes confirmed the loss of midgut binding to Cry1Ab and Cry1Ac in the resistant larvae. The loss of midgut binding to Cry1Ab/Cry1Ac is inherited as a recessive trait, which is consistent with the recessive inheritance of Cry1Ab/Cry1Ac resistance in this greenhouse-derived T. ni population. Therefore, it is concluded that the mechanism for the greenhouse-evolved Cry1Ac resistance in T. ni is an alteration affecting the binding of Cry1Ab and Cry1Ac to the Cry1Ab/Cry1Ac binding site in the midgut.
