Genetic engineering of rice for resistance to homopteran insect pests

The rice brown planthopper (BPH; Nilaparvata lugens) is a serious pest of rice crops throughout Asia, damaging plants both through its feeding behavior and by acting as a virus vector. Like many homopteran pests of crops, it is primarily a phloem feeder, abstracting sap via specially adapted mouthparts. An artificial diet bioassay system for this pest was developed to allow the effects of potentially insecticidal proteins to be assayed. Several lectins and oxidative enzymes were found to be toxic to BPH. Snowdrop (Galanthus nivalis) lectin (GNA) was selected for further study as it is nontoxic to higher animals. A cDNA encoding GNA was assembled into constructs for expression in transgenic plants, with the aim of producing transgenic rice plants that would express the foreign protein in their phloem sap and be resistant to BPH. Constitutive expression of GNA in model plant systems was shown to have deleterious effects on the development of lepidopteran and homopteran pest insects. Phloem-specific promoters for expressing GNA in transgenic rice were isolated and characterized with the aim of increasing the effectiveness and specificity of the protection against BPH. A construct containing the GNA coding sequence driven by the promoter from the rice sucrose synthase RSs1 gene was tested in tobacco and transformed into rice. Transgenic rice plants containing this construct are currently being evaluated.