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Enhanced Resistance to Seed-Transmitted Bacterial Diseases in Transgenic Rice Plants Overproducing an Oat Cell-Wall-Bound Thionin

June 2002 , Volume 15 , Number  6
Pages  515 - 521

Takayoshi Iwai , 1 , 3 H. Kaku , 1 R. Honkura , 2 S. Nakamura , 2 H. Ochiai , 1 T. Sasaki , 1 Y. Ohashi 1 , 3

1National Institute of Agrobiological Sciences, Kannondai, Tsukuba, Ibaraki 305-8602, Japan; 2Miyagi Prefectural and Horticulture Research Center, Takadate-kawakami, Natori, Miyagi 981-1243, Japan; 3Core Research of Evolutional Science and Technology (CREST), Chiyodaku, Tokyo 101-0062, Japan

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Accepted 5 February 2002.

Bacterial attack is a serious agricultural problem for growth of rice seedlings in the nursery and field. The thionins purified from seed and etiolated seedlings of barley are known to have antimicrobial activity against necrotrophic pathogens; however, we found that no endogenous rice thionin genes alone are enough for resistance to two major seed-transmitted phytopathogenic bacteria, Burkholderia plantarii and B. glumae, although rice thionin genes constitutively expressed in coleoptile, the target organ of the bacteria. Thus, we isolated thionin genes from oat, one of which was overexpressed in rice. When wild-type rice seed were germinated with these bacteria, all seedlings were wilted with severe blight. In the seedling infected with B. plantarii, bacterial staining was intensively marked around stomata and intercellular spaces. However, transgenic rice seedlings accumulating a high level of oat thionin in cell walls grew almost normally with bacterial staining only on the surface of stomata. These results indicate that the oat thionin effectively works in rice plants against bacterial attack.

© 2002 The American Phytopathological Society