Timing of development - The role of SRR1 at the intersection between circadian timekeeping and flowering time control

在它们的生命周期中，植物经历了三个不同的发育阶段。在最初的幼年阶段，植物还没有获得对促进开花的环境信号做出反应的能力。在随后的成体营养阶段，植物获得了开花能力，但在环境条件适合繁殖之前，植物专注于获得生物量。在最后的繁殖阶段，植物重新分配其资源来生产花朵和后代。这些阶段之间的过渡需要仔细把握时机，以确保生殖成功。影响这些转变的一个主要环境信号是昼长，由生物钟测量。这种内源的生物计时器通过促进花整合基因开花位点T(FT)的表达来刺激春夏长日的开花，开花基因T(FT)被认为是长期寻找的成花的一部分。对红光减少1(SRR1)的敏感性是一种先驱蛋白，对生物钟的正确节奏和开花时间的控制至关重要。我们最近证实，SRR1通过促进FT的几个抑制因子的表达，在非诱导性短日照中起到了抑制开花的作用。这一建议旨在研究SRR1如何在分子水平上调节开花时间。由于SRR1对于正确的时钟节奏是必需的，它很可能与其他时钟蛋白相互作用。因此，将进行SRR1与组成生物钟夜间复合体的蛋白质之间的相互作用研究。为了揭示在开花时间控制中与SRR1协同作用的其他基因，将在EMS诱变的srr1-1突变体群体中进行第二个位点抑制子筛选。将对诱变植物进行筛选，寻找能够缓解srr1-1显著早花表型的第二个位点突变。这些突变将通过连锁作图和全基因组测序相结合的方式进行识别。初步数据显示，SRR1与染色质有关。因此，将使用CHIP-SEQ对基因组中的SRR1靶标进行全球图谱分析。这也将揭示是否有任何共同的结合基序是SRR1结合DNA所必需的。这些方法的结合将有助于我将SRR1放入开花时间网络，并解释SRR1如何在分子水平上调节拟南芥重要的生长期转换。

During their life cycle, plants progress through three distinct developmental stages. In the initial juvenile phase, the plant has not yet acquired the ability to respond to flowering-promoting environmental signals. In the following adult vegetative phase the plant has acquired flowering competence but is focused on acquiring biomass until environmental conditions are suitable for reproduction. In the final reproductive phase, the plant reallocates its resources to produce flowers and offspring. The transition between these phases needs to be carefully timed to ensure reproductive success. A major environmental signal influencing these transitions is the daylength, measured by the circadian clock. This endogenous, biological timekeeper stimulates flowering in long spring and summer days, by promoting the expression of the floral integrator gene FLOWERING LOCUS T (FT), considered to be part of the long sought florigen.SENSITIVITY TO RED LIGHT REDUCED 1 (SRR1) is a pioneer protein that is important for correct pacing of the circadian clock and for flowering time control. We have recently established that SRR1 acts as a repressor of flowering in noninductive short days, by promoting expression of several repressors of FT. This proposal aims at studying how SRR1 acts on the molecular level to regulate flowering time. As SRR1 is necessary for the correct pace of the clock, it is likely to interact with other clock proteins. Therefore, interaction studies between SRR1 and the proteins making up the evening complex of the circadian clock will be performed. To reveal additional genes that act in concert with SRR1 in flowering time control, a second site suppressor screen will be performed on an EMS-mutagenized population of srr1-1 mutants. Mutagenized plants will be screened for second site mutations that alleviate the prominent early flowering phenotype of srr1-1. These mutations will then be identified through a combination of linkage mapping and full genome sequencing. Preliminary data show that SRR1 associates with chromatin. Thus, a global profiling of SRR1 targets in the genome will be performed using ChIP-Seq. This will also reveal whether there are any common binding motifs necessary for SRR1 association of the DNA. The combination of these approaches will help me placing SRR1 into the flowering time network and explain how SRR1 acts on the molecular level to regulate important growth stage transitions in Arabidopsis.