Study on the Role of OsRZFP34-Mediated Transpiration in Rice Thermotolerance(2/3)

By oligo microarray expression profiling, we identified a rice RING zinc-finger protein (RZFP), OsRZFP34,whose gene expression increased with high temperature or abscisic acid (ABA) treatment. As compared with thewild type, rice and Arabidopsis with OsRZFP34 overexpression showed increased relative stomata opening evenwith ABA treatment. Analysis of water loss and leaf temperature under stress conditions revealed a higherevaporation rate and cooling effect in OsRZFP34-overexpressing rice than the wild type. Transcription profilingof transgenic rice overexpressing OsRZFP34 revealed many genes involved in OsRZFP34-mediated stomatalmovement. Several genes upregulated OsRZFP34-overexpressing plants were previously implicated in Ca2+sensing, K+ regulator, and ABA response such as OsCBP, OsHAK5, and OsWRKY80 genes. We suggest thatOsRZFP34 may modulate these genes to control stomata opening and transpiration. In this three-year project, weare trying to study the role and regulatory mechanism of OsRZFP34 for stomatal opening and transpiration.Firstly, we are focused on understanding the upstream and downstream pathway of OsRZFP34-mediated stomataopening and transpiration. We plan to determine the roles of OsHSFB4b and OsHSFB2b on activatingOsRZFP34 gene expression under heat stress, which can show that the two OsHSFs are involved in stomataopening and closing and heat dissipation. In addition, we plan to confirm that OsRZFP34 modulates OsCBP,OsHAK5, and OsWRKY80 genes to cont rol stomata opening, guard cell calcium reduction andtranspiration. Secondly, we will analyze the role of OsRZFP34 in rice thermotolerance. We plan to measurethermotolerance and yield of OsRZFP34-overexpressing rice plants after high temperature treatment. Theseresults are helpful to support that high transpiration can enhance rice yield.