Phytochrome B regulates Heading date 1 (Hd1)-mediated expression of rice florigen Hd3a and critical day length in rice

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Ryo Ishikawa, Mayumi Aoki, Ken-ichi Kurotani, Shuji Yokoi, Tomoko Shinomura, Makoto Takano, Ko Shimamoto
Molecular Genetics and Genomics, 2011, 285(6): 461-470  DOI: 10.1007/s00438-011-0621-4;      追溯原文......本站官方QQ群:62473826
Flowering – Florigen – Oryza sativa – Photoperiod – Phytochrome B

Many plants require circadian clock and light information for the photoperiodic control of flowering. In Arabidopsis, a long-day plant (LDP), flowering is triggered by the circadian clock-controlled expression of CONSTANS (CO) and light stabilization of the CO protein to induce FT (FLOWERING LOCUS T). In rice, a short-day plant (SDP), the CO ortholog Heading date 1 (Hd1) regulates FT ortholog Hd3a, but regulation of Hd3a by Hd1 differs from that in Arabidopsis. Here, we report that phytochrome B (phyB)-mediated suppression of Hd3a is a primary cause of long-day suppression of flowering in rice, based on the three complementary discoveries. First, overexpression of Hd1 causes a delay in flowering under SD conditions and this effect requires phyB, suggesting that light modulates Hd1 control of Hd3a transcription. Second, a single extension of day length decreases Hd3a expression proportionately with the length of daylight. Third, Hd1 protein levels in Hd1-overexpressing plants are not altered in the presence of light. These results also suggest that phyB-mediated suppression of Hd3a expression is a component of the molecular mechanism for critical day length in rice.

光敏色素B调节Hd1介导的水稻成花素Hd3a的表达和临界日长

许多植物需要生物钟和光周期信号来调控开花。对于长日照植物(LDP)拟南芥,生物钟调节CONSTANS(CO)的表达,光稳定CO蛋白,诱导FT表达,促使植物开花。短日照植物(SDP)水稻中,CO的同源基因Hd1调节FT的同源基因Hd3a,但是Hd1对Hd3a表达的调节方式是不同于拟南芥的。本文作者报道了光敏色素B(PhyB)介导的抑制Hd3a表达,是长日照抑制水稻开花的主要原因。首先过量表达Hd1,在短日照条件下延迟水稻开花是需要phyB参与的,表明光调控Hd1调节Hd3a的转录。其次,仅仅延长单次日长就能够降低Hd3a表达,并且程度对应于日照长度。最后,在存在光的条件下,Hd1蛋白水平在Hd1过表达植株中并没有发生变化。这些结果还表明,phyB介导的抑制Hd3a的表达是水稻临界日长分子机制中的一个组成元件。


基因列表
  抽穗期基因 Hd1
  成花素基因;抽穗期基因;生育期基因;光周期敏感基因;感光基因 Hd3a; FT
  光敏色素B PHYB; OsphyB