Regulation of Flowering Time by Trehalose-6-Phoshate Signaling

开花的诱导是植物生活史中的一个中心事件。由于其重要性，开花是在一个复杂的遗传电路，整合内源性（激素，碳水化合物，年龄）和环境信号（温度，光周期）的控制下。在诱导光周期下，拟南芥开花时间的关键调节因子FLOWERLOCUS T（FT）在叶片维管系统中被诱导，并作为长距离信号在茎分生组织处启动开花。二糖海藻糖-6-磷酸（T6 P）已被证明是协调碳水化合物状态与发育过程的信号分子。缺乏T6 P合成酶海藻糖-6-磷酸合酶1（TPS 1）的拟南芥植物开花极晚。我们最近发现，TPS 1/T6 P信号调节整个植物的几个开花时间基因的表达。在叶维管系统中，T6 P/TPS 1是诱导FT所绝对需要的，而在茎顶端分生组织（SAM）MIR 156及其靶点处，T6 P/TPS信号传导靶向SQUAMOSA启动子结合蛋白样（SPL）基因。环境（光周期）和生理（T6 P/TPS 1）信号一起确保开花仅在条件最佳时开始，即，日长超过某一最小值并且碳水化合物状态支持向开花和种子生产的能量需求过渡。然而，许多关于T6 P/TPS 1的功能的问题仍然是开放的。在这里，我们提出了一系列的实验，旨在更好地整合T6 P/TPS 1信号到经典的开花时间途径。我们的初步结果表明，T6 P/TPS 1调节开花的部分通过调节细胞周期依赖的SAM维护，以前未探索的方面，我们希望进一步调查。此外，我们有初步的证据表明，T6 P/TPS 1影响植物的能力，以应对环境温度的变化，以及冷却（春化）处理。将分析T6 P/TPS 1途径与开花的温度依赖性调节之间的联系。除了上述的分析，集中在已知的基因和途径，我们还将确定T6 P/TPS 1信号通路的新组件。为此，我们已经进行了一个大规模的诱变筛选，以确定抑制剂晚开花的tps 1突变体。作为优先计划的一部分，我们将详细鉴定和表征致病基因，并将其置于T6 P/TPS 1信号通路中。总之，拟议的实验将提供有价值的洞察碳水化合物信号和开花时间途径的整合。

The induction of flowering is a central event in the life cycle of plants. Because of its importance, flowering is under the control of a complex genetic circuitry that integrates endogenous (hormones, carbohydrates, age) and environmental signals (temperature, photoperiod). Under inductive photoperiod, FLOWERING LOCUS T (FT), a key regulator of flowering time in Arabidopsis thaliana, is induced in the leaf vasculature and acts as a long distance signal to initiate flowering at the shoot meristem. The disaccharide trehalose-6-phosphate (T6P) has been shown to act as signalling molecule in coordinating carbohydrate status with developmental processes. Arabidopsis thaliana plants deficient in the T6P-synthesizing enzyme TREHALOSE-6-PHOSPHATE SYSNTHASE 1 (TPS1) flower extremely late. We recently showed that TPS1/T6P signalling regulates the expression of several flowering-time genes throughout the plant. In the leaf vasculature T6P/TPS1 is absolutely required for the induction of FT, whereas at the shoot apical meristem (SAM) MIR156 and its targets, the SQUAMOSA PROMOTER BINDING PROTEIN LIKE (SPL) genes are targeted by T6P/TPS signalling. Together the environmental (photoperiod) and physiologic (T6P/TPS1) signals ensure that flowering commences only when the conditions are optimal, that is, day length exceeds a certain minimum and the carbohydrate status supports the energy-demanding transition to flowering and seed production. However, many questions regarding the function of T6P/TPS1 remain open.Here we propose a series of experiments with the aim to better integrate T6P/TPS1 signalling into the canonical flowering time pathways. Our preliminary results suggest that T6P/TPS1 regulates flowering in part through the modulation of cell-cycle-dependent SAM maintenance, a previously unexplored aspect that we wish to investigate further. In addition, we have preliminary evidence that T6P/TPS1 affects the ability of plants to respond to changes in ambient temperature as well as chilling (vernalization) treatments. The connection between the T6P/TPS1 pathway and the temperature-dependent regulation of flowering will be analysed. Apart from the above-mentioned analyses that focus on known genes and pathways we will also identify novel components of the T6P/TPS1 signalling pathway. To this end we have already carried out a large-scale mutagenesis screen to identify suppressors of late flowering of the tps1 mutant. As part of the priority program we will identify and characterize in detail the causal genes and place them into the T6P/TPS1 signalling pathway. In summary, the proposed experiments will provide valuable insight into the integration of carbohydrate signalling and flowering time pathways.