Molecular dissection of the roles of phytochrome in photoperiodic flowering in rice

6.535
Asami Osugi, Hironori Itoh, Kyoko Ikeda-Kawakatsu, Makoto Takano, Takeshi Izawa
Plant Physiology, 2011, 157(3): 1128-1137  DOI: 10.1104/pp.111.181792;      追溯原文......本站官方QQ群:62473826

Phytochromes mediate the photoperiodic control of flowering in rice (Oryza sativa), a short-day plant. Recent molecular genetics studies have revealed a genetic network that enables the critical daylength response of florigen gene expression. Analyses using a rice phytochrome chromophore-deficient mutant, photoperiod sensitivity5, have so far revealed that within this network, phytochromes are required for expression of Grain number, plant height and heading date7 (Ghd7), a floral repressor gene in rice. There are three phytochrome genes in rice, but the roles of each phytochrome family member in daylength response have not previously been defined. Here, we revealed multiple action points for each phytochrome in the critical daylength response of florigen expression by using single and double phytochrome mutant lines of rice. Our results show that either phyA alone or a genetic combination of phyB and phyC can induce Ghd7 mRNA, whereas phyB alone causes some reduction in levels of Ghd7 mRNA. Moreover, phyB and phyA can affect Ghd7 activity and Early heading date1 (a floral inducer) activity in the network, respectively. Therefore, each phytochrome gene of rice has distinct roles, and all of the phytochrome actions coordinately control the critical daylength response of florigen expression in rice.

对光敏色素在水稻光周期开花途径中作用的分子剖析

水稻是一种短日照植物,光敏色素参与了光周期调控的水稻开花。近来分子遗传研究揭示了一个遗传网络可以使成花素基因对临界日长做出应答。利用一个光敏色素发色团缺陷突变体photoperiod sensitivity5,发现在这个网络中光敏色素对开花抑制因子基因Ghd7 的表达是必需的。水稻中有3个光敏色素基因,但是每个光敏色素家族成员对日照长度的应答之前还未有研究。本研究通过水稻光敏色素单突变和双突变株系,揭示了不同光敏色素在成花素基因应答日照长度的过程的多种作用。结果表明单独phyA 或者phyB、phyC 共同作用可以诱导Ghd7 mRNA的积累,而phyB 单独作用可以一定程度降低Ghd7 mRNA水平。此外phyB 和phyA 可以分别影响网络中Ghd7 和Hd1(一个开花诱导子)的活性。因此,水稻中每个光敏色素基因都有着独特的作用,这些光敏色素协同调控水稻成花素基因的表达对临界日长的应答。


基因列表
  早穗基因 Ehd1
  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
  每穗粒数、株高和抽穗期多效性控制基因 Ghd7
  光敏色素A PHYA
  水稻开花抑制因子 OsCOL4
  成花素基因 RFT1; FT-L3
  光敏色素B PHYB; OsphyB
  光敏色素C PHYC