Overexpression of the RIXI xylanase inhibitor improves disease resistance to the fungal pathogen, Magnaporthe oryzae, in rice

Abstract

In this paper we focus our attention on RIXI, a member of the XIP type xylanase inhibitor proteins in rice. RIXI-overexpression transgenic lines were generated by expressing the RIXI gene under the control of auliflower mosaic virus 35S promoter. In comparison with the wild-type (WT) plants, the transgenic plants had significantly increased levels of RIXI and showed resistance to Magnaporthe oryzae. Transgenic plants also contained higher levels of H2O2 and had larger changes in catalase and superoxide dismutase activities than the WT plants. The results showed that the increase in RIXI expression was accompanied by the up-regulation of pathogenesis-related genes and genes related to the jasmonate signaling pathway. To clarify the expression pattern of RIXI, a ProRIXI: GUS vector was constructed and transgenic rice lines were obtained. GUS staining results suggested that the RIXI gene possessed distinctive, tissue-specific and grow stage-specific expression patterns in rice. This is the first report on the expression patterns of rice xylanase inhibitors and our results provide direct evidence, at the plant level, that xylanase inhibitors are involved in plant defense against fungal pathogens.