Photoperiodic flowering is one of the most important pathways to govern flowering in rice （Oryza sativa）, in which Heading date 1 （Hdl）, an ortholog of the Arabidopsis CONSTANS gene, encodes a pivotal regulator. H...Photoperiodic flowering is one of the most important pathways to govern flowering in rice （Oryza sativa）, in which Heading date 1 （Hdl）, an ortholog of the Arabidopsis CONSTANS gene, encodes a pivotal regulator. Hdl promotes flowering under short-day conditions （SD） but represses flowering under long-day conditions （LD） by regulating the expression of Heading date 3a （Hd3a）, the FLOWERING LOCUS T （FT） ortholog in rice. However, the molecular mechanism of how Hdl changes its regulatory activity in response to day length remains largely unknown. In this study, we demonstrated that the repression of flowering in LD by Hdl is dependent on the transcription factor DAYS TO HEADING 8 （DTHS）. Loss of DTH8 function results in the activation of Hd3a by Hdl, leading to early flowering. We found that Hdl directly interacts with DTH8 and that the formation of the DTH8-Hd1 complex is necessary for the transcriptional repression of Hd3a by Hdl in LD, implicating that the switch of Hdl function is mediated by DTH8 in LD rather than in SD. Furthermore, we revealed that DTH8 associates with the Hd3a promoter to modulate the level of H3K27 trimethylation （H3K27me3） at the Hd3a locus. In the presence of the DTH8-Hdl complex, the H3K27me3 level was increased at Hd3a, whereas loss of DTH8 function resulted in decreased H3K27me3 level at Hd3a. Taken together, our findings indicate that, in response to day length, DTH8 plays a critical role in mediating the transcriptional regulation of Hd3a by Hdl through the DTH8-Hd1 module to shape epigenetic modifications in photoperiodic flowering.展开更多
基金This work was supported by the National Natural Science Foundation （31501278, 31671378 to X.O.）, the National Key Research and Development Program of China （2017YFA0506100 to X.H.） and the Fundamental Research Funds for the Central Universities （20720170068 to X.O. and 20720150098 to X.H.）.
文摘Photoperiodic flowering is one of the most important pathways to govern flowering in rice （Oryza sativa）, in which Heading date 1 （Hdl）, an ortholog of the Arabidopsis CONSTANS gene, encodes a pivotal regulator. Hdl promotes flowering under short-day conditions （SD） but represses flowering under long-day conditions （LD） by regulating the expression of Heading date 3a （Hd3a）, the FLOWERING LOCUS T （FT） ortholog in rice. However, the molecular mechanism of how Hdl changes its regulatory activity in response to day length remains largely unknown. In this study, we demonstrated that the repression of flowering in LD by Hdl is dependent on the transcription factor DAYS TO HEADING 8 （DTHS）. Loss of DTH8 function results in the activation of Hd3a by Hdl, leading to early flowering. We found that Hdl directly interacts with DTH8 and that the formation of the DTH8-Hd1 complex is necessary for the transcriptional repression of Hd3a by Hdl in LD, implicating that the switch of Hdl function is mediated by DTH8 in LD rather than in SD. Furthermore, we revealed that DTH8 associates with the Hd3a promoter to modulate the level of H3K27 trimethylation （H3K27me3） at the Hd3a locus. In the presence of the DTH8-Hdl complex, the H3K27me3 level was increased at Hd3a, whereas loss of DTH8 function resulted in decreased H3K27me3 level at Hd3a. Taken together, our findings indicate that, in response to day length, DTH8 plays a critical role in mediating the transcriptional regulation of Hd3a by Hdl through the DTH8-Hd1 module to shape epigenetic modifications in photoperiodic flowering.
