SRWD1, a novel target gene of DELLA and WRKY proteins, participates in the development and immune response of rice (Oryza sativa L.)

SRWD1, a member of the WD40 protein subfamily, is induced by salt stress in rice and its homolog in barley can bind to GAMYB, implying that SRWD1 might be involved in plant defense against environmental stress and gibberellic acid (GA) signalings. In this study, we focused on the biological functions and regulation mechanisms of SRWD1 in rice. The results showed that SRWD1 expression was repressed by GA and induced by abscisic acid (ABA). Two WRKY-family transcription factors, OsWRKY45 and OsWRKY72, were found to regulate SRWD1 expression by directly binding to the W-box region in its promoter. Transient co-expression and yeast two-hybrid analyses showed that a DELLA protein strengthened the activation of OsWRKY45 and partly relieved the suppression of OsWRKY72 by binding to them. Interestingly, both SRWD1-overexpressing transgenic plants and SRWD1-knockout mutants showed dwarf phenotypes and resistance to Xanthomonas oryzae.