Photoperiodic control of floral transition in Arabidopsis thaliana

为了确保繁殖成功，植物发展了一个复杂的遗传网络，将内源和环境因素整合在一起，以正确地确定开花的时间。控制这种发育转换的最重要因素之一是日长，或者说光周期。根据嫁接实验，有人提出，光周期在叶片中被感知，在那里它导致一种称为成花素的成花物质的诱导。然后，成花素被传递到枝尖，在那里它诱导过渡到开花。在过去的70年里，成花素的分子性质一直难以确定，但最近的数据表明，成花基因T(FT)的mRNA可以从叶片传递到顶端，在顶端FT蛋白与bZIP转录因子Fd相互作用诱导成花。我们已经发现了一种花转换的负调控因子，SCHLAFMätze(SMZ)，它能抑制叶片中FT的诱导。SMZ和其他影响FT转录或mRNA稳定性的基因或FT蛋白水平的错误表达的结果表明，FT蛋白的运动可能在开花诱导中起关键作用。在这里，我们提出了一系列实验来研究SMZ在调节FT转录中的功能，包括miR172在这一过程中的潜在作用。我们将进一步分析FT蛋白是否能够从叶片移动到顶端。具体地说，我们将解决FT蛋白质运动是否可能的问题，正如我们的初步数据所表明的那样，以及这种运动是否是诱导开花的必要和充分的。最后，我们将分析FT/Fd蛋白复合体在茎尖的作用，重点是识别直接靶标。

To ensure reproductive success, plants have developed an elaborate genetic network that integrates endogenous and environmental factors to correctly time the onset of flowering. One of the most important factors that control this developmental switch is day length, or photoperiod. Based on grafting experiments it has been proposed that photoperiod is perceived in leaves where it leads to the induction of a flower-forming substance called florigen . The florigen is than transmitted to the shoot apex where it induces the transition to flowering. The molecular nature of the florigen has eluded characterization for the past 70 years, but recent data suggest that the mRNA of FLOWERING LOCUS T (FT) can be transmitted from the leaves to the apex where the FT protein interacts with a bZIP transcription factor FD to induce flowering. We have identified a negative regulator of floral transition, SCHLAFMÜTZE (SMZ), which represses the induction of FT in leaves. Results from misexpression of SMZ and other genes that affect either FT transcription or mRNA stability, or the FT protein level suggest the FT protein movement might be crucial for the induction of flowering. Here we propose a series of experiments to investigate the function of SMZ in regulating FT transcription, including the potential role of miR172 in this process. We will further analyze whether FT protein is able to move from the leaves to the apex. Specifically we will address the question whether FT protein movement is possible at all, as is suggested from our preliminary data, and whether this movement is necessary and sufficient to induce flowering. Finally we will analyze the role of FT/FD protein complex at the shoot apex with an emphasis on identifying direct targets.