Rice transcription factor WRKY68 plays a positive role in <italic>Xa21</italic>-mediated resistance to <italic>Xanthomonas oryzae</italic> pv. <italic>oryzae</italic>

Abstract

<p id="C3">Leaf blight is a bacterial disease of rice which leads to heavy yield losses. <italic>Xa21</italic> which harbors broad spectrum resistance to leaf blight is the first resistant gene cloned in rice and is widely used in rice breeding program. The identification of transcription factor involved in <italic>Xa21</italic>-mediated resistance to bacterial leaf blight is of great significance. In this study, transgenic <italic>WRKY68-RNAi</italic> lines with reduced expression level of WRKY68 protein in the background of <italic>Xa21 </italic>were generated. The <italic>WRKY68-RNAi</italic> transgenic lines showed reduced resistance to <italic>Xanthomonas oryzae</italic> pv. <italic>oryzae </italic>(<italic>Xoo</italic>), indicating that <italic>WRKY68</italic> played a positive role in <italic>Xa21</italic>-mediated resistance in rice. No detectable changes of WRKY68 protein abundance in leaves at different stages and positions after inoculation were identified by Western blot, indicating that the expression of WRKY68 protein were independent of <italic>Xa21</italic> and <italic>Xoo</italic>, and thus <italic>WRKY68</italic> gene may function as a transcription factor to regulate downstream genes. It was further found that the abundance of a number of pathogenesis-related proteins, including PR1A, PR5, PR10A, PR-pha, and PAL1 were dramatically changed in <italic>WRKY68-RNAi</italic> transgenic lines when inoculated with <italic>Xoo</italic>, suggested that these pathogenesis-related proteins were regulated by <italic>WRKY68 </italic>and the corresponding genes were involved in the downstream defenses responses.