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Binary toxins from Bacillus thuringiensis active against the western corn rootworm, Diabrotica virgifera virgifera LeConte.

ABSTRACT: The western corn rootworm, Diabrotica virgifera virgifera LeConte, is a significant pest of corn in the United States. The development of transgenic corn hybrids resistant to rootworm feeding damage depends on the identification of genes encoding insecticidal proteins toxic to rootworm larvae. In this study, a bioassay screen was used to identify several isolates of the bacterium Bacillus thuringiensis active against rootworm. These bacterial isolates each produce distinct crystal proteins with approximate molecular masses of 13 to 15 kDa and 44 kDa. Insect bioassays demonstrated that both protein classes are required for insecticidal activity against this rootworm species. The genes encoding these proteins are organized in apparent operons and are associated with other genes encoding crystal proteins of unknown function. The antirootworm proteins produced by B. thuringiensis strains EG5899 and EG9444 closely resemble previously described crystal proteins of the Cry34A and Cry35A classes. The antirootworm proteins produced by strain EG4851, designated Cry34Ba1 and Cry35Ba1, represent a new binary toxin. Genes encoding these proteins could become an important component of a sustainable resistance management strategy against this insect pest.

SUBMITTER: Baum JA

PROVIDER: S-EPMC492402 | biostudies-literature | 2004 Aug

REPOSITORIES: biostudies-literature

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Binary toxins from Bacillus thuringiensis active against the western corn rootworm, Diabrotica virgifera virgifera LeConte.

Baum James A JA Chu Chi-Rei CR Rupar Mark M Brown Gregory R GR Donovan William P WP Huesing Joseph E JE Ilagan Oliver O Malvar Thomas M TM Pleau Michael M Walters Matthew M Vaughn Ty T

Applied and environmental microbiology 20040801 8

The western corn rootworm, Diabrotica virgifera virgifera LeConte, is a significant pest of corn in the United States. The development of transgenic corn hybrids resistant to rootworm feeding damage depends on the identification of genes encoding insecticidal proteins toxic to rootworm larvae. In this study, a bioassay screen was used to identify several isolates of the bacterium Bacillus thuringiensis active against rootworm. These bacterial isolates each produce distinct crystal proteins with ...[more]

PMID: 15294828

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Project description:The western corn rootworm, Diabrotica virgifera virgifera (LeConte) (Coleoptera: Chrysomelidae), is an economically important pest of corn in the northern United States. Some populations have developed resistance to management strategies including transgenic corn that produces insecticidal toxins derived from the bacterium Bacillus thuringiensis (Bt). Knowledge of insect dispersal is of critical importance for models of resistance evolution. Larval density affects survival in the field, and stress from crowding often affects facultative long-distance dispersal of adult insects. In this study, we used laboratory flight mills to characterize western corn rootworm flight performance as a function of larval rearing density. Larvae were reared under three densities and the resulting adult females were either allowed to fly voluntarily for 22 h or forced to fly specified durations. For both experiments we also measured lifetime fecundity following flight. The three rearing densities placed differential levels of stress on individuals, as evidenced by decreased survival to adulthood and decreased size of adults at greater rearing density. When larvae were reared under crowded conditions the resulting females were more likely to engage in flight activity, including long uninterrupted flights lasting >10 min, than those reared under low density conditions. Flight and egg production are both energy intensive processes. However, we found no evidence in either voluntary or forced flight experiments of a tradeoff between flight activity and female fecundity. The results suggest that females emerging from high density populations in cornfields are more likely to disperse and disperse farther than those emerging from low density populations. These results are important because they imply that variation in population density in the landscape will affect dispersal, which may in turn require computer models of resistance evolution to incorporate multiple dispersal rates arising from varying larval densities among fields.

Dataset Information

Binary toxins from Bacillus thuringiensis active against the western corn rootworm, Diabrotica virgifera virgifera LeConte.

Publications

Binary toxins from Bacillus thuringiensis active against the western corn rootworm, Diabrotica virgifera virgifera LeConte.

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