Abstract
Rice WRKY45 is a transcriptional activator essential for BTH-induced disease resistance. Transgenic rice plants overexpressing WRKY45 (WRKY45-ox) exhibit strong resistance to blast and leaf-blight diseases. Although WRKY45 is transcriptionally upregulated by SA/BTH, its post-transcriptional regulation has been elusive.
To characterize post-transcriptional regulation of WRKY45, we generated transgenic rice constitutively expressing myc-WRKY45. We found that myc-WRKY45 highly accumulated by proteasome inhibitor MG132 and was polyubiquitinated in vivo, suggesting that WRKY45 is degraded by ubiquitin-proteasome system. Protein accumulation by MG132 was also observed for endogenous WRKY45 by using anti-WRKY45 antibody. Preferential accumulation of hyper-phosphorylated WRKY45 by MG132 led us to determine phosphorylation sites in WRKY45 by peptide mass fingerprinting and to investigate the influence of the phosphorylation on WRKY45 protein stability. Moreover, we analyzed the relationship between protein degradation and transcriptional activity of WRKY45. Based on results, we will discuss the regulation of WRKY45 activity by proteasome-mediated degradation.
