Transgenic rice expressing wasabi defensin gene exhibit its enhanced resistance to blast fungus (Magnaporthe grisea)

A complementary DNA of defensin gene was isolated from wasabi (Wasabiajaponica) plant. This cDNA was cloned into PVX (Potato virus X) vector, and the vector inoculated to Nicotiana benthamiana plants to rapidly produce the defensin protein in planta. Purified wasabi defensin showed strong antimicrobial activity toward Magnaporthe grisea. Thus, wasabi defensin gene fused with a strong maize ubiquitin promoter was used for transformation of rice (Oryza saliva cv. Sasanishiki) by Agrobacterium tumefaciens-mediated method. Transformants exhibited resistance to rice blast at various levels. Inheritance of blast resistance over the generations was confirmed. Two T3 lines (WT14-5 and WT43-5) stably expressing the defensin protein were challenged with blast fungus by using the press-injured spots inoculation method. The average size of disease lesions of the transgenic line WT43-5 was reduced to about half of that of non-transgenic plants. Transgenic rice plants producing wasabi defensin are expected to possess a durable and wide-spectrum resistance (i.e. field resistance) against various rice blast races.