Riboni Matteo, Robustelli Test Alice, Galbiati Massimo, Tonelli Chiara, Conti Lucio
Department of BioSciences, Università degli Studi di Milano, Via Celoria 26, 20133, Milan, Italy.
Department of BioSciences, Università degli Studi di Milano, Via Celoria 26, 20133, Milan, Italy
J Exp Bot. 2016 Dec;67(22):6309-6322. doi: 10.1093/jxb/erw384. Epub 2016 Oct 12.
One strategy deployed by plants to endure water scarcity is to accelerate the transition to flowering adaptively via the drought escape (DE) response. In Arabidopsis thaliana, activation of the DE response requires the photoperiodic response gene GIGANTEA (GI) and the florigen genes FLOWERING LOCUS T (FT) and TWIN SISTER OF FT (TSF). The phytohormone abscisic acid (ABA) is also required for the DE response, by promoting the transcriptional up-regulation of the florigen genes. The mode of interaction between ABA and the photoperiodic genes remains obscure. In this work we use a genetic approach to demonstrate that ABA modulates GI signalling and consequently its ability to activate the florigen genes. We also reveal that the ABA-dependent activation of FT, but not TSF, requires CONSTANS (CO) and that impairing ABA signalling dramatically reduces the expression of florigen genes with little effect on the CO transcript profile. ABA signalling thus has an impact on the core genes of photoperiodic signalling GI and CO by modulating their downstream function and/or activities rather than their transcript accumulation. In addition, we show that as well as promoting flowering, ABA simultaneously represses flowering, independent of the florigen genes. Genetic analysis indicates that the target of the repressive function of ABA is the flowering-promoting gene SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1), a transcription factor integrating floral cues in the shoot meristem. Our study suggests that variations in ABA signalling provide different developmental information that allows plants to co-ordinate the onset of the reproductive phase according to the available water resources.
植物用来抵御缺水的一种策略是通过干旱逃避（DE）反应适应性地加速向开花的转变。在拟南芥中，DE反应的激活需要光周期反应基因GIGANTEA（GI）以及成花素基因FLOWERING LOCUS T（FT）和FT的姊妹基因（TSF）。植物激素脱落酸（ABA）通过促进成花素基因的转录上调，对DE反应也是必需的。ABA与光周期基因之间的相互作用模式仍不清楚。在这项研究中，我们采用遗传学方法证明ABA调节GI信号传导，从而影响其激活成花素基因的能力。我们还发现，ABA依赖的FT激活需要CONSTANS（CO），而TSF则不需要，并且破坏ABA信号传导会显著降低成花素基因的表达，而对CO转录本水平影响很小。因此，ABA信号传导通过调节光周期信号传导核心基因GI和CO的下游功能和/或活性，而非其转录本积累，来对它们产生影响。此外，我们发现ABA除了促进开花外，还能独立于成花素基因抑制开花。遗传分析表明，ABA抑制功能的靶标是促进开花的基因CONSTANS过表达抑制因子1（SOC1），它是一种整合茎尖分生组织中开花信号的转录因子。我们的研究表明，ABA信号传导的变化提供了不同的发育信息，使植物能够根据可用水资源协调生殖阶段的开始。
