Exploring the Ehd1-independent flowering pathway under short-day conditions in rice

초록

The transition from vegetative to reproductive growth is one of the most important processes contributing to grain yield in rice. Under inductive conditions, flowering promotion in rice is facilitated by the florigens (Hd3a and RFT1), which are induced by Ehd1, a grass-specific master activator. However, a comprehensive understanding of the role of this gene and the mechanisms of flowering promotion in its absence is still required. To investigate the function of Ehd1, we used the CRISPR/Cas9 method to generate ehd1 mutants. These mutants showed a 20-day delay in flowering compared to the wild type (WT) under natural paddy field conditions. To study the Ehd1-independent flowering mechanism, we performed short-day (SD) treatments on 40-day-old WT and ehd1 mutants initially grown under long-day (LD) conditions. The WT plant flowered after 40 days of SD treatment, whereas the mutants exhibited delayed flowering, which occurred after 56 days. Transcriptome analysis revealed a significant up-regulation of Ehd1, HDAC3 and OsSFL1 in ehd1 mutants compared to WT. It has been reported that OsSFL1 functions as a flowering activator and that the OsSFL1-HDAC complex represses target gene transcription by reducing histone H3 acetylation under SD conditions. To further investigate the role of OsSFL1, we generated ehd1 ossfl1 double mutants that exhibited similar heading dates to ehd1 mutants under SD conditions, suggesting that OsSFL1 is involved in the Ehd1-dependent flowering pathway.