The Korean Soclety of Plant Pathology : G ; Molecular Plant-Microbe Interactions : G-23 ; Molecular characterization of OsWRKY6 that bind to the W-box like element 1 of OsPR10a promoter and confer reduced susceptibility to pathogen

WRKY proteins are transcription factors (TFs) that regulate the expres-sion of defense-related genes. Among SA inducible WRKY TFs OsWRKY6 was identified as a positive regulator of OsPR10a by transient expression assays. The physical interaction between the W-box-like element 1 (WLE1), which positively regulates OsPR10a/PBZ1 expression, and OsWRKY6 was verified in vitro. Several PR genes including OsPR10a are constitutively activated; enhanced disease resistance to pathogens was shown in trans-genic plants overexpressing (ox) OsWRKY6. By contrast, PR gene induction was compromised in transgenic OsWRKY6-RNAi lines, suggesting that OsWRKY6 is a positive regulator of defense responses. OsWRKY6ox lines displayed lesions on their leaves, and increased OsWRKY6 levels cause cell death. SA levels were higher in OsWRKY6ox lines than that in WT and tran-script level of OsICS1, which encodes a major enzyme for SA biosynthesis, was increased in OsWRKY6ox lines compared to WT. OsWRKY6 directly bound to the OsICS1 promoter in vivo. This indicates that OsWRKY6 can directly regulate OsICS1 and then increases SA levels. OsWRKY6 auto-regulates its own expression. OsWRKY6 protein degradation is possibly regulated by ubiquitination and stabilized by SA treatment. Our results suggest that OsWRKY6 positively regulates defense responses through OsICS1 activation and OsWRKY6 stabilization.