RESUMO
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.
Assuntos
Adiantum/genética , Glycine max/genética , Inseticidas , Mariposas , Controle Biológico de Vetores , Proteínas de Plantas/genética , Zea mays/genética , Animais , Proteção de Cultivos , Plantas Geneticamente Modificadas , Proteínas Recombinantes/toxicidadeRESUMO
The coleopteran insect western corn rootworm (WCR, Diabrotica virgifera virgifera) is an economically important pest in North America and Europe. Transgenic corn plants producing Bacillus thuringiensis (Bt) insecticidal proteins have been useful against this devastating pest, but evolution of resistance has reduced their efficacy. Here, we report the discovery of a novel insecticidal protein, PIP-47Aa, from an isolate of Pseudomonas mosselii. PIP-47Aa sequence shows no shared motifs, domains or signatures with other known proteins. Recombinant PIP-47Aa kills WCR, two other corn rootworm pests (Diabrotica barberi and Diabrotica undecimpunctata howardi) and two other beetle species (Diabrotica speciosa and Phyllotreta cruciferae), but it was not toxic to the spotted lady beetle (Coleomegilla maculata) or seven species of Lepidoptera and Hemiptera. Transgenic corn plants expressing PIP-47Aa show significant protection from root damage by WCR. PIP-47Aa kills a WCR strain resistant to mCry3A and does not share rootworm midgut binding sites with mCry3A or AfIP-1A/1B from Alcaligenes that acts like Cry34Ab1/Cry35Ab1. Our results indicate that PIP-47Aa is a novel insecticidal protein for controlling the corn rootworm pests.
Assuntos
Bacillus thuringiensis/metabolismo , Zea mays/metabolismo , Zea mays/microbiologia , Animais , Controle Biológico de Vetores , Plantas Geneticamente Modificadas/metabolismo , Plantas Geneticamente Modificadas/microbiologiaRESUMO
RNA interference (RNAi) in transgenic maize has recently emerged as an alternative mode of action for western corn rootworm (Diabrotica virgifera virgifera) control which can be combined with protein-based rootworm control options for improved root protection and resistance management. Currently, transgenic RNAi-based control has focused on suppression of genes that when silenced lead to larval mortality. We investigated control of western corn rootworm reproduction through RNAi by targeting two reproductive genes, dvvgr and dvbol, with the goal of reducing insect fecundity as a new tool for pest management. The results demonstrated that exposure of adult beetles, as well as larvae to dvvgr or dvbol dsRNA in artificial diet, caused reduction of fecundity. Furthermore, western corn rootworm beetles that emerged from larval feeding on transgenic maize roots expressing dvbol dsRNA also showed significant fecundity reduction. This is the first report of reduction of insect reproductive fitness through plant-mediated RNAi, demonstrating the feasibility of reproductive RNAi as a management tool for western corn rootworm.
Assuntos
Controle Biológico de Vetores , Doenças das Plantas/genética , Interferência de RNA , Reprodução/genética , Animais , Besouros/genética , Besouros/patogenicidade , Fertilidade/genética , Proteínas de Insetos/genética , Larva/genética , Larva/patogenicidade , Doenças das Plantas/microbiologia , Plantas Geneticamente Modificadas/genética , RNA de Cadeia Dupla/genética , RNA de Plantas/genética , Zea mays/genética , Zea mays/crescimento & desenvolvimento , Zea mays/microbiologiaRESUMO
The coleopteran insect western corn rootworm (WCR) (Diabrotica virgifera virgifera LeConte) is a devastating crop pest in North America and Europe. Although crop plants that produce Bacillus thuringiensis (Bt) proteins can limit insect infestation, some insect populations have evolved resistance to Bt proteins. Here we describe an insecticidal protein, designated IPD072Aa, that is isolated from Pseudomonas chlororaphis. Transgenic corn plants expressing IPD072Aa show protection from WCR insect injury under field conditions. IPD072Aa leaves several lepidopteran and hemipteran insect species unaffected but is effective in killing WCR larvae that are resistant to Bt proteins produced by currently available transgenic corn. IPD072Aa can be used to protect corn crops against WCRs.
Assuntos
Proteínas de Bactérias/metabolismo , Besouros/metabolismo , Resistência a Inseticidas , Inseticidas/metabolismo , Doenças das Plantas/parasitologia , Raízes de Plantas/parasitologia , Plantas Geneticamente Modificadas/parasitologia , Pseudomonas chlororaphis/metabolismo , Zea mays/parasitologia , Animais , Toxinas de Bacillus thuringiensis , Proteínas de Bactérias/classificação , Proteínas de Bactérias/genética , Besouros/genética , Produtos Agrícolas/genética , Produtos Agrícolas/parasitologia , Endotoxinas/genética , Endotoxinas/metabolismo , Proteínas Hemolisinas/genética , Proteínas Hemolisinas/metabolismo , Filogenia , Raízes de Plantas/genética , Plantas Geneticamente Modificadas/genética , Zea mays/genéticaRESUMO
RNA interference (RNAi) is a promising new technology for corn rootworm control. This paper presents the discovery of new gene targets - dvssj1 and dvssj2, in western corn rootworm (WCR). Dvssj1 and dvssj2 are orthologs of the Drosophila genes snakeskin (ssk) and mesh, respectively. These genes encode membrane proteins associated with smooth septate junctions (SSJ) which are required for intestinal barrier function. Based on bioinformatics analysis, dvssj1 appears to be an arthropod-specific gene. Diet based insect feeding assays using double-stranded RNA (dsRNA) targeting dvssj1 and dvssj2 demonstrate targeted mRNA suppression, larval growth inhibition, and mortality. In RNAi treated WCR, injury to the midgut was manifested by "blebbing" of the midgut epithelium into the gut lumen. Ultrastructural examination of midgut epithelial cells revealed apoptosis and regenerative activities. Transgenic plants expressing dsRNA targeting dvssj1 show insecticidal activity and significant plant protection from WCR damage. The data indicate that dvssj1 and dvssj2 are effective gene targets for the control of WCR using RNAi technology, by apparent suppression of production of their respective smooth septate junction membrane proteins located within the intestinal lining, leading to growth inhibition and mortality.
