Moon Jihyun, Suh Sung-Suk, Lee Horim, Choi Kyu-Ri, Hong Choo Bong, Paek Nam-Chon, Kim Sang-Gu, Lee Ilha
School of Biological Sciences, Seoul National University, Seoul 151-742, Korea.
Plant J. 2003 Sep;35(5):613-23. doi: 10.1046/j.1365-313x.2003.01833.x.
The floral transition in Arabidopsis is regulated by at least four flowering pathways: the long-day, autonomous, vernalization, and gibberellin (GA)-dependent pathways. Previously, we reported that the MADS-box transcription factor SUPPRESSOR OF OVEREXPRESSION OF CO 1 (SOC1) integrates the long-day and vernalization/autonomous pathways. Here, we present evidences that SOC1 also integrates signaling from the GA-dependent pathway, a major flowering pathway under non-inductive short days. Under short days, the flowering time of GA-biosynthetic and -signaling mutants was well correlated with the level of SOC1 expression; overexpression of SOC1 rescued the non-flowering phenotype of ga1-3, and the soc1 null mutant showed reduced sensitivity to GA for flowering. In addition, we show that vernalization-induced repression of FLOWERING LOCUS C (FLC), an upstream negative regulator of SOC1, is not sufficient to activate SOC1; positive factors are also required. Under short days, the GA pathway provides a positive factor for SOC1 activation. In contrast to SOC1, the GA pathway does not regulate expression of other flowering integrators FLC and FT. Our results explain why the GA pathway has a strong effect on flowering under short days and how vernalization and GA interact at the molecular level.
长日照途径、自主途径、春化途径和赤霉素（GA）依赖途径。此前，我们报道过MADS盒转录因子CO 1过表达抑制子（SOC1）整合了长日照途径与春化/自主途径。在此，我们提供证据表明，SOC1还整合了来自GA依赖途径的信号，GA依赖途径是在非诱导性短日照条件下的一条主要开花途径。在短日照条件下，GA生物合成和信号转导突变体的开花时间与SOC1的表达水平密切相关；SOC1的过表达挽救了ga1 - 3的不开花表型，而soc1缺失突变体对GA诱导开花的敏感性降低。此外，我们发现春化诱导的开花位点C（FLC）的抑制，FLC是SOC1的上游负调控因子，并不足以激活SOC1；还需要正调控因子。在短日照条件下，GA途径为SOC1的激活提供了一个正调控因子。与SOC1不同，GA途径不调控其他开花整合因子FLC和FT的表达。我们的结果解释了为什么GA途径在短日照条件下对开花有强烈影响，以及春化和GA在分子水平上是如何相互作用的。
