Differential Expression of Rice Valine-Qlutamine Gene Family in Response to Nitric Oxide and Regulatory Circuit of OsVQ7 and OsWRKY24

The functional diversity of plant valine-qlutamine(VQ) proteins is closely associated with their partners WRKY transcription factors, and also with a complex network of signaling pathways that mediated by hormone molecules. We reported genome-wide expression profiles of differentially expressed rice VQ genes under nitric oxide(NO) treatment based on a microarray analysis. Cluster analysis of expression patterns revealed that some VQ genes and WRKY genes shared similar expression trends. Prediction of cis-elements showed that W-box or W-box-like sequences were overrepresented within the promoters of most of NO-responsive VQ genes. In particular, the similarly expressed Os VQ7 and Os WRKY24 showed great induction upon NO triggering. Transient expression assay and chromatin immunoprecipitation analysis demonstrated that OsWRKY24 was specifically bound to the promoter regions of Os VQ7 and Os WRKY24 itself, which contain multiple copies of W-box or W-box-like cis-elements. Yeast-two-hybrid assay indicated that OsWRKY24 can interact physically with OsVQ7 through the C-terminal of WRKY domain. The results suggested that OsVQ7 and OsWRKY24 may form an auto-and cross-regulation circuit that is required for tight regulation and fine-tuning of physiological processes they are involved in. These findings provided a solid foundation for exploring the specific functions of the VQ protein family in NO signaling pathway.