RESUMO
The vegetative insecticidal protein Vip3Aa from Bacillus thuringiensis (Bt) has been produced by transgenic crops to counter pest resistance to the widely used crystalline (Cry) insecticidal proteins from Bt. To proactively manage pest resistance, there is an urgent need to better understand the genetic basis of resistance to Vip3Aa, which has been largely unknown. We discovered that retrotransposon-mediated alternative splicing of a midgut-specific chitin synthase gene was associated with 5,560-fold resistance to Vip3Aa in a laboratory-selected strain of the fall armyworm, a globally important crop pest. The same mutation in this gene was also detected in a field population. Knockout of this gene via CRISPR/Cas9 caused high levels of resistance to Vip3Aa in fall armyworm and 2 other lepidopteran pests. The insights provided by these results could help to advance monitoring and management of pest resistance to Vip3Aa.
Assuntos
Bacillus thuringiensis , Proteínas de Bactérias , Quitina Sintase , Resistência a Inseticidas , Retroelementos , Animais , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Quitina Sintase/genética , Quitina Sintase/metabolismo , Retroelementos/genética , Bacillus thuringiensis/genética , Resistência a Inseticidas/genética , Sistemas CRISPR-Cas , Processamento Alternativo/genética , Processamento Alternativo/efeitos dos fármacos , Spodoptera/efeitos dos fármacos , Plantas Geneticamente Modificadas , Mariposas/efeitos dos fármacos , Mariposas/genéticaRESUMO
Transgenic crops producing Bacillus thuringiensis (Bt) toxins are commonly used for controlling insect pests. Nearby refuges of non-Bt host plants play a central role in delaying the evolution of resistance to Bt toxins by pests. Pervasive fitness costs associated with resistance, which entail lower fitness of resistant than susceptible individuals in refuges, can increase the ability of refuges to delay resistance. Moreover, these costs are affected by environmental factors such as host plant suitability, implying that manipulating refuge plant suitability could improve the success of the refuge strategy. Based on results from a previous study of Trichoplusia ni resistant to Bt sprays, it was proposed that low-suitability host plants could magnify costs. To test this hypothesis, we investigated the association between host plant suitability and fitness costs for 80 observations from 30 cases reported in 18 studies of 8 pest species from 5 countries. Consistent with the hypothesis, the association between plant suitability and fitness cost was negative. With plant suitability scaled to range from 0 (low) to 1 (high), the expected cost was 20.7% with a suitability of 1 and the fitness cost increased 2.5% for each 0.1 decrease in suitability. The most common type of resistance to Bt toxins involves mutations affecting a few types of midgut proteins to which Bt toxins bind to kill insects. A better understanding of how such mutations interact with host plant suitability to generate fitness costs could be useful for enhancing the refuge strategy and sustaining the efficacy of Bt crops.
Assuntos
Toxinas de Bacillus thuringiensis , Bacillus thuringiensis , Aptidão Genética , Resistência a Inseticidas , Mariposas , Animais , Resistência a Inseticidas/genética , Mariposas/crescimento & desenvolvimento , Mariposas/genética , Mariposas/fisiologia , Plantas Geneticamente Modificadas , Endotoxinas , Proteínas Hemolisinas , Controle Biológico de Vetores , Proteínas de Bactérias , Produtos AgrícolasRESUMO
Biopesticides based on RNA interference (RNAi) took a major step forward with the first registration of a sprayable RNAi product, which targets the world's most damaging potato pest. Proactive resistance management is needed to delay the evolution of resistance by pests and sustain the efficacy of RNAi biopesticides.