Centro de Biotecnología y Genómica de Plantas, Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria-Universidad Politécnica de Madrid, 28223 Madrid, Spain.
Plant Cell. 2012 Mar;24(3):982-99. doi: 10.1105/tpc.110.081885. Epub 2012 Mar 9.
The Arabidopsis thaliana early in short days6 (esd6) mutant was isolated in a screen for mutations that accelerate flowering time. Among other developmental alterations, esd6 displays early flowering in both long- and short-day conditions. Fine mapping of the mutation showed that the esd6 phenotype is caused by a lesion in the high expression of osmotically responsive genes1 (HOS1) locus, which encodes a RING finger-containing E3 ubiquitin ligase. The esd6/hos1 mutation causes decreased flowering locus C expression and requires CONSTANS (CO) protein for its early flowering phenotype under long days. Moreover, CO and HOS1 physically interact in vitro and in planta, and HOS1 regulates CO abundance, particularly during the daylight period. Accordingly, hos1 causes a shift in the regular long-day pattern of expression of flowering locus T (FT) transcript, starting to rise 4 h after dawn in the mutant. In addition, HOS1 interacts synergistically with constitutive photomorphogenic1, another regulator of CO protein stability, in the regulation of flowering time. Taken together, these results indicate that HOS1 is involved in the control of CO abundance, ensuring that CO activation of FT occurs only when the light period reaches a certain length and preventing precocious flowering in Arabidopsis.
拟南芥短日照 6 期（esd6）突变体是在筛选加速开花时间的突变体时分离出来的。除了其他发育改变外，esd6 在长日和短日条件下均表现出早花。该突变的精细定位表明，esd6 表型是由高表达渗透响应基因 1（HOS1）基因座的病变引起的，该基因座编码一个含 RING 指的 E3 泛素连接酶。esd6/hos1 突变导致开花位点 C 的表达减少，并且在长日照条件下需要 CONSTANS（CO）蛋白才能表现出早花表型。此外，CO 和 HOS1 在体外和体内相互作用，并且 HOS1 调节 CO 丰度，特别是在白天期间。因此，hos1 导致开花位点 T（FT）转录本的正常长日表达模式发生变化，在突变体中，FT 转录本在黎明后 4 小时开始上升。此外，HOS1 与另一种 CO 蛋白稳定性调节剂组成型光形态建成 1（constitutive photomorphogenic1）在调控开花时间方面具有协同作用。综上所述，这些结果表明 HOS1 参与 CO 丰度的调控，确保只有当光周期达到一定长度时，CO 才能激活 FT，从而防止拟南芥过早开花。
