Dioscorea batatas tuber lectin 1 (DB1) is a storage protein isolated from yam tuber and has been shown to be a mannose-binding lectin. Here we produced transgenic rice plants expressing cDNA of DB1 under the control of phloemspecific promoter of rice sucrose synthase-1 gene. DB1 accumulated at a level of 0.07% of total soluble protein. We then evaluated its efficacy for brown planthopper (BPH). After releasing the first instar of BPH on the transgenic rice plants, the number of survived BPH adults was reduced up to 30% compared to that of wild-type rice. The number of the next generation BPH was suppressed to 22% on average in the seven most-resistant plants compared to that of wild-type rice plants when female adult BPH was inoculated. These results demonstrated that DB1 is effective to confer BPH resistance in terms of decreased survival and fecundity.Key words: Dioscorea batatas tuber lectin 1, insect resistance, planthopper, transgenic rice.Three major sap-sucking pests of rice in Japan: brown planthopper (Nilaparvata lugens, BPH), whitebacked planthopper (Sogatella furcifera, WBPH) and small brown planthopper (Laodelphax striatellus) are known to cause severe damage to rice by sucking or acting as vectors for major viral disease. Recently, these pests have developed resistance to most commercial chemical pesticides (Matsumura et al. 2008). A transgenic approach has been explored to confer rice plants with resistance to such sap-sucking insects. One of the promising genes is encoding mannose-binding protein such as snowdrop lectin (Galanthus nivalis agglutinin; GNA) and garlic leaf lectin (Allium sativum agglutinin from leaf; ASAL). Expression of GNA or ASAL in rice plants has been shown to confer substantial resistance to BPH, WBPH, and green rice planthopper in terms of increased insect mortality, retarded development and decreased fecundity (Rao et al. 1998;Nagadhara et al. 2003Nagadhara et al. , 2004Saha et al. 2006a; Yarashi et al. 2008). Mannose-binding proteins, in general, are known to bind to mannose-containing glycoproteins in the mid-guts of insects, and inhibit growth and development (Sauvion et al. 1996).We have been focusing on Dioscorea batatas tuber lectin 1 (DB1), which has been isolated from yam tuber, Dioscorea batatas Decne., as a storage protein. DB1 is considered to be least non-harmful to human beings, as we Japanese eat raw tubers without boiling them. DB1 is a mannose-binding lectin (23 kDa) consisting of identical 12-kDa subunits. It has 58% and 48% amino-acid identity to GNA and ASAL, respectively, and is classified in the GNA-related lectin family (Gaidamashvili et al. 2004). The insecticidal properties of DB1 have been reported against moth larvae (Helicoverpa armigera). The rate of adults emerging from pupae was reduced to 33%, when fed on 0.01% (w/v) DB1 in an artificial diet (Ohizumi et al. 2009). We also demonstrated that ≥1 mg/ml DB1 in an artificial diet significantly decreased the survival and fecundity of green peach aphid, Myzus persicaeca (Kato et al. 2010). Th...

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