Analyses Of OsWRKY11and OsRBS1in Rice

Rice is one of the world’s most important food crops. Disease resistance and flowering time are two hot spots in rice research. In this study, we characterized a semidwarf and late flowering (dlfl) mutation of rice that has pleiotropic effects on these traits. The dlfl mutation was caused by a T-DNA insertion and the cloned Dlfl gene was found to encode a WRKY transcription factor (OsWRKYll). The dlfl mutant contains a T-DNA insertion at the promoter region, leading to enhanced accumulation of Dlfl transcripts, resulting in a semidominant mutation. The dlfl mutant exhibited enhanced susceptibility against Magnaporthe. oryzae compared to the wild type controls. The dlfl mutation suppressed the transcription of Ehd2/RID1/Osldl and its downstream flowering time genes including Hdl, Ehd1and Hd3a under both long-day (LD) and short-day (SD) conditions. Knock-down of Dlfl expression exhibited early flowering at LD condition related to the wild-type plants. Two splicing forms of Dlfl cDNAs were obtained (OsWRKYll.1and OsWRKY11.2). Enhanced expression of OsWRKY11.2or its N’truncated gene showed similar phenotypes to the dlfl mutant, suggesting that it might function as a negative regulator. We conclude that Dlfl overexpression causes late flowering by downregulating Ehd2/RID1/OsIdl in the signal transduction pathway of flowering and enhanced susceptibility to the rice pathogens M.oryzae.The rice U-box/ARM E3ubiquitin ligase SPL11(Spotted leaf11) negatively regulates programmed cell death (PCD) and controls flowering time. In spill mutant shows enhanced resistance to both M. oryzae and Xanthomonas oryzae pv oryzae. SPIN1(for SPL11-interacting proteinl) encodes a RNA binding protein containing a single KH domain and interacts with SPLll in the nucleus. Overexpression of SPIN1causes late flowering in transgenic rice under short-day (SD) and long-day (LD) conditions. RBS1(RNA-binding and SPIN1-interacting1) was identified in a yeast-two-hybrid screen using the full-length SPIN1cDNA as a bait and encodes an RNA binding protein with three RNA recognition motifs. The protein interacts with SPIN1in the nucleus. Moreover, like SPIN1transgennic plants, no enhanced resistance or susceptibility was observed when both RBS1-overexpressed and silenced lines were inoculated with CHNOS strains of M. oryzae compared with wild type NPB. These results suggested that RBS1might not be involved in the disease resistance signaling.RBSl overexpression causes delayed flowering under SD and LD conditions in rice. Expression analyses of flowering marker genes show that RBS1overexpression represses the expression of Hd3a under SD and LD conditions. RBS1is upregulated in both SPINl overexpression plants and in the spill mutant. Interestingly, SPIN1expression is increased but SPL11expression is repressed in the RBS1overexpression plants. Western blot analysis revealed that the SPIN1protein level is increased in the RBS1overexpression plants and that the RBS1protein level is also up-regulated in the SPIN1overexpression plants. These results suggest that RBSl is a new negative regulator of flowering time that itself is positively regulated by SPIN1but negatively regulated by SPL11in rice.