Genetically modified crops that express insecticidal (Bt) proteins have become a primary approach for control of lepidopteran (moth) and coleopteran (beetle) pests that feed by chewing the plants. However， the sap-sucking insects (Hemiptera) are not particularly susceptible to Bt toxins. In this study， we describe two Cry toxins (Cry64Ba and Cry64Ca) from Bt strain 1012 that showed toxicity against two important hemipteran rice pests， and Both of these proteins contain an ETX/MTX2 domain and share common sequence features with the β-pore-forming toxins. Coexpression of and genes in the acrystalliferous Bt strain HD73 resulted in high insecticidal activity against both hemipteran pests. No toxicity w... More
Genetically modified crops that express insecticidal (Bt) proteins have become a primary approach for control of lepidopteran (moth) and coleopteran (beetle) pests that feed by chewing the plants. However， the sap-sucking insects (Hemiptera) are not particularly susceptible to Bt toxins. In this study， we describe two Cry toxins (Cry64Ba and Cry64Ca) from Bt strain 1012 that showed toxicity against two important hemipteran rice pests， and Both of these proteins contain an ETX/MTX2 domain and share common sequence features with the β-pore-forming toxins. Coexpression of and genes in the acrystalliferous Bt strain HD73 resulted in high insecticidal activity against both hemipteran pests. No toxicity was observed on other pests such as ， ， or Also， no hemolytic activity or toxicity against cancer cells was detected. Binding assays showed specific binding of the Cry64Ba/Cry64Ca toxin complex to brush border membrane vesicles isolated from Cry64Ba and Cry64Ca are Bt Cry toxins highly effective against hemipteran pests and could provide a novel strategy for the environmentally friendly biological control of rice planthoppers in transgenic plants. In Asia， rice is an important staple food， whose production is threatened by rice planthoppers. To date， no effective (Bt) protein has been shown to have activity against rice planthoppers. We cloned two Bt toxin genes from Bt strain 1012 that showed toxicity against small brown planthoppers () and white-backed planthoppers (). To our knowledge， the proteins encoded by the and genes are the most efficient insecticidal Bt Cry proteins with activity against hemipteran insects reported so far. Cry64Ba and Cry64Ca showed no toxicity against some lepidopteran or coleopteran pests. These two proteins should be able to be used for integrated hemipteran pest management.
