OsBAK1 is involved in rice resistance to Xanthomonas oryzae pv. oryzae PXO99

OsBAK1 gene belongs to a receptor like kinase gene family in rice and shares a highly conserved gene structure and sequence homology with Arabidopsis thaliana BAK1 gene. To investigate the role of OsBAK1 in rice immunity, the full-length cDNA of OsBAK1 was isolated by RT-PCR and the transgenic rice lines (over expression and RNA-interference lines) were generated using Agrobacterium -mediated transformation. The expression level of OsBAK1 was determined by q-PCR in overexpression and RNAi transgenic rice lines. Based on quantitative polymerase chain reaction (q-PCR) results, two overexpression lines and two RNAi lines were evaluated in bioassays for resistance to Xanthomonas oryzae pv. oryzae PXO99, the causal agent of rice bacterial blight disease. Pathogenicity bioassays showed overexpression OsBAK1 lines exhibited resistance to blight disease whereas OsBAK1 RNAi lines promoted susceptibility. Besides, OsBAK1 can complement the function of AtBAK1 in Arabidopsis bak1 protoplast, activating FRK1 expression, a marker gene in PTI signaling pathway, after treatment by flg22. Furthermore, the transcriptional level of OsBAK1 was induced significantly in rice by defense signaling molecules such as salicylic acid, jasmonic acid, and PXO99 inoculation. Our results illustrated OsBAK1 positively regulates plant defense against rice bacterium pathogen Xanthomonas oryzae pv. oryzae PXO99.