Feedback transcription regulation between OsNAC3 and OsDREB1A promotes postgermination growth in rice.

Abstract

Early postgermination growth is critical for the success of direct seeding in rice cultivation. However, the underlying mechanism determining postgermination growth of rice is largely unknown. Here, we report the rice OsDREB1A-OsNAC3-OsGA20ox1 transcriptional module that positively regulates the early postgermination growth through the gibberellic acid (GA) pathway. Transcription factor OsDREB1A improves postgermination growth by OsNAC3-mediated increase of GA biosynthesis. OsNAC3 can directly bind to the promoter of GA biosynthesis gene <i>OsGA20ox1</i>, which consequently activates its expression and increases GA content during the early postgermination growth stage. Furthermore, the expressions of <i>OsDREB1A</i> and <i>OsNAC3</i> are positively regulated by each other, and the cis-regulatory polymorphisms in promoters fine-tune their corresponding expressions to determine the natural variations of postgermination growth. The transferred elite haplotypes of <i>OsNAC3</i> and <i>OsDREB1A</i> and overexpression of both genes in <i>japonica</i> varieties contribute postgermination growth. The application of OsDREB1A and OsNAC3 is useful for the development of rice varieties for direct seeding cultivation.