OsbZIP75 positively regulates plant defense against the bacterial leaf blight pathogen Xanthomonas oryzae pv. oryzae

Basic leucine zipper (bZIP) proteins are involved in various biological processes, including biotic and abiotic stress responses. In response to biotic stress in rice (Oryza sativa L.), the roles of the TGA class of OsbZIP proteins are well-characterized, whereas those of the non-TGA class of OsbZIP proteins remain largely unknown. Here, we analyze the function of OsbZIP75/RF2a in defense against Xanthomonas oryzae pv. oryzae (Xoo). The expression of OsbZIP75/RF2a was increased in response to infection with an incompatible Xoo race at 6 h post-inoculation, and rice plants overexpressing OsbZIP75/RF2a showed reduced symptom than wild-type plants upon infection with a compatible Xoo race. Defense related genes, especially OsPR10a, were up-regulated in OsbZIP75(OX) plants, and OsbZIP75/RF2a activated the OsPR10a promoter in a transient expression assay. Overall, these results indicate that OsbZIP75/RF2a acts as a positive regulator of defense against Xoo.