Study On A High Temperature Responsive Transcription Factor, OsHRT2, In Rice

Grain yield and quality is controlled genetically and can also be influenced by the environmental factors, especially by high temperature during heading and milky stages. In our previous studies, a high temperature responsive transcription factor, OsHRT2, which is expressed highly in rice panicle was identified by bioinformatics analysis. Here, we isolated a T-DNA insertion line of this gene, hrt2 which is a null mutant. The hrt2 mutant exhibited cleistogamy, and had closed spikelets, reduced plant height, erect leaves, decreased panicle and seed size. We also obtained some genetic materials of OsHRT2 gene by using reverse genetic methods, knocking down (RNAi and TALEN) or over-expressing this gene’s expression.OsHRT2 RNAi plants show similar phenotype with hrt2 mutant while the plants over-expressing OsHRT2 showed enhanced bending of the lamina joint and increased grain size. Furthermore, the OsHRT2 gene can be induced by JA, BR and wounding stimuli. Expression analyses showed that OsHRT2 gene is expressed in several organs including root, lamina joint, pistil and stamen. All these results suggest that this novel bHLH transcription factor OsHRT2 may be involved in the regulation of floret opening through BR and JA pathways. Further investigation will help us to determine the function of OsHRT2 gene in floret opening and plant development.