Natural variation of flowering time due to cis-regulatory evolution of FLOWERING LOCUS T and its orthologs and paralogs in Brassica napus

在许多植物中，开花基因T及其相关蛋白是将光周期信息从叶片传递到地上部的移动信号，在地上部实现了向开花的过渡。FT的表达在转录水平上受到严格控制，因此它仅限于叶片，只在适当的光周期中出现，并整合了环境温度和发育线索，以及关于生物和非生物胁迫的信息。我们以前在模式植物拟南芥中证实了FT转录需要近端的启动子顺式元件和远端的增强子，两者都在十字花科物种中进化保守。此外，在两年生材料中，FT转录在春化前被阻止，FT的春化依赖性受位于第一内含子的Carg-box控制，该内含子与转录抑制物开花基因C(FLC)结合。染色质介导的多梳群(PcG)途径的抑制是光周期依赖的FT调控所必需的，并参与了对其他信号的FT表达水平的调节。在这个项目中，我建议探索拟南芥1001基因组计划中的可用序列数据，以评估FT调控顺式元件的变化频率以及这些变化如何转化为适应性值。根据不同的环境条件，将测定不同材料的F1代的等位基因特异的FT表达模式。显示顺式调节变异的FT等位基因将被进一步分析，以确定因果调节变化并更详细地研究其影响。甘蓝型油菜(Brassica Napus)是异源四倍体甘蓝型油菜(Brassica Napus)的杂交种，它们分别属于A型和C型基因组，由于大约10×106年前发生的基因组三倍体，甘蓝型油菜是中多倍体。我们将从一组甘蓝型油菜的两个基因组中确定FT类同源基因的等位基因特异性表达。这些植物将在不断变化的环境条件下在田间种植，以最大限度地提高检测副冠目动物表达变异的机会。我们将比较创始人基因组对调节开花时间的贡献，并评估这种贡献的差异。一个特别的焦点将是研究染色质介导的抑制对甘蓝型油菜等位基因选择的影响。

In many plant species, FLOWERING LOCUS T and related proteins are the mobile signal that communicates information on photoperiod from the leaves to the shoots, where the transition to flowering is realized. FT expression is tightly controlled at the transcriptional level so that it is restricted to leaves, occurs only in appropriate photoperiods, and integrates ambient temperature and developmental cues, as well as information on biotic and abiotic stress. We previously established that FT transcription in the model plant Arabidopsis thaliana requires proximal promoter cis-elements and a distal enhancer, both evolutionary conserved among Brassicacea species. In addition, FT transcription is blocked prior vernalization in biannual accessions and vernalization-dependency of FT is controlled through a CArG-box located in the first intron that binds the transcriptional repressor FLOWERING LOCUS C (FLC). Chromatin-mediated repression by the Polycomb Group (PcG) pathway is required for photoperiod-dependent FT regulation and participates in FT expression level modulation in response to other cues.In this project, I propose to explore the available sequence data from the 1001 genome project in Arabidopsis to evaluate how often changes in regulatory cis-elements at FT have occurred and how these translate into an adaptive value. Allele-specific FT expression pattern will be measured in F1 hybrids of different accessions in response to varying environmental conditions. FT alleles that show cis-regulatory variation will be further analyzed to pinpoint the causal regulatory changes and study their effect in more detail. The allotetrapolyploid species Brassica napus is a hybrid of two Brassiceae species belonging to the A- and C-type genome, which are in turn mesopolyploid due to a genome triplication that occurred ca. 10x106 years ago. We will determine allele-specific expression of FT paralogs from both genomes of a collection of B. napus accessions. The plants will be grown in the field in changing environmental conditions to maximize the chance to detect expression variation of the paralogs. We will compare the contribution of the founder genomes to the regulation of flowering time and asses variation in this contribution. A particular focus will be to study the impact of chromatin-mediated repression on allele selection in B. napus.