Study On A BZIP Transcription Factor, OsbZIP2, In Rice (Oryza Sativa L.)

Rice seed size which is controlled genetically and can also be influenced by the environmental factors is an important agronomic trait in determining grain yield and quality. In our previous studies, a bZIP transcription factor, OsbZIP2, which is expressed highly in the rice panicle was identified by bioinformatics analysis. Here, we obtained some genetic materials of OsbZIP2 gene by using reverse genetic methods, including knocking down (RNAi and TALEN)or overexpressing this gene’s expression. The grain length of OsbZIP2 RNAi transgenic seeds was increased 7%, compared to the nontransgenic control (ZH11). After analyzing the OsbZIP2Pro::GUS transgenic plants, we found the OsbZIP2 gene is highly expressed in the root and vascular tissue of spikelet hull. The expression level of OsbZIP2 gene is much higher in the early developmental stage of spikelet hull than that in the late developmental stage. RT-PCR results showed that CAK1A gene which is involved in the regulation of cell cycle was greatly downregulated in the OsbZIP2 RNAi transgenic plants. All these results suggest that this novel bZIP transcription factor OsbZIP2 may be involved in the regulation of rice seed size by controlling the cell cycle of spikelet hull at the early developmental stage. In addition, OsbZIP2 gene can be induced by high temperature stress, and repressed by drought and ABA stimuli. Further investigation will help us to determine the function of OsbZIP2 gene in seed size controlling and biotic stress response.