拟南芥转录因子RBE、JAG 和TCP5时空特异调节花瓣生长过程的机理研究

Plant organ development is a highly ordered process. At the cellular level, early stage organs usually consist of cells undergoing active cell divisions. As the organ grows, certain cells will cease division and enter the phase of cell differentiation. This transition often occurs in a temporal and spatial specific fashion that largely determines the final size and shape of the organ. Recent studies have uncovered a number of genes involved in controlling cell division and differentiation during plant organ development, however, our understanding of the gene network regulating the temporal and spatial changes in organ growth is still limited. In this project, we propose to utilize the Arabidopsis petal as a model system to further study the temporal and spatial regulatory mechanisms of plant organ growth. Specifically, we will focus on investigating three key transcription factors that we analyzed previously, RBE, JAG and TCP5, which conduct temporal and spatial-specific roles during petal growth: RBE and JAG are expressed at the stages and regions with active cell divisions, and function to promote cell division and petal growth. In contrast, TCP5 is localized in the cells with low division activities, and acts as a negative regulator of cell division and petal growth. We propose to employ genomic approaches, such as transcriptome analysis, in combination with other genetic, molecular and developmental biology techniques to characterize the interactions of the downstream genetic networks of the three genes. Through these experiments, we aim to elucidate how these three genes function together in the temporal and spatial regulation of petal growth. In the long term, we hope to use these results as a launch pad for further understanding the general mechanisms that establish temporal and spatial patterns of plant organ development.

植物器官发育是一个高度有序的过程，从细胞层面来看，会经历细胞分裂由活跃到终止，继而进入分化阶段的转变。此转变发生的时空特异性极大决定了器官最终的大小与形状。现有的研究已经发现了一系列调控细胞分裂分化的基因，但对这些基因如何协同控制器官生长的时空变化仍然缺乏足够的认识。本项目针对这一问题，在模式植物拟南芥花瓣里深入探究器官生长的时空调节机理。本课题组前期研究了三个在花瓣生长特定阶段和部位起关键作用的转录因子：RBE、JAG 和TCP5。RBE和JAG在细胞分裂活跃的时空区域表达，并促进细胞分裂和花瓣生长；TCP5表达局限在细胞分裂活性低的区域，它恰好是细胞分裂和生长负调控基因。本项目中，我们将利用转录组分析等基因组学方法结合其他遗传、分子及发育生物学手段研究三个基因下游调控网络及相互关系，由此阐明三者如何共同作用调节花瓣生长的时空变化过程，并以此为基础，深入剖析植物器官发育的时空调节机理。

植物器官生长是一个高度有序的过程，受复杂的分子机理时空特异调控，对这些机理的全面解析是领域内研究的一大热点。拟南芥花瓣是研究植物器官生长的重要模式系统，前期研究发现了RBE，JAG和TCP5三个在花瓣生长中时空特异调节细胞分裂、体积扩增及分化的转录因子，但它们的下游调控网络还有待深入挖掘。本课题针对这一问题，综合基因组学、遗传及分子生物学等方法，详细解析了三个关键转录因子调控的基因库，鉴定了多个在器官发育中起关键作用的新基因和新调节通路。我们通过筛选RBE下游候选基因，发现RBE可以通过直接抑制负调控生长的CIN-TCP基因TCP4而调节花瓣生长中细胞分裂向体积扩增过程的转变。我们还在RBE下游鉴定了一个新的生长调节基因--编码E3泛素连接酶的PUB25，并发现PUB25在植物器官发育中起着抑制细胞分裂作用。而RBE可以直接调控PUB25并抑制其表达，从而影响花瓣早期生长。我们还通过鉴定和完善JAG与TCP5的下游基因库，并将其进行比较，发现它们共同调节一系列赤霉素（GA）功能相关，特别是在赤霉素代谢途径中起关键作用的基因。此外，我们还发现TCP5可以通过促进TALE基因家族中的KNAT3和SAW1而调节叶片边缘发育。我们希望上述的研究结果为进一步认识RBE，JAG和TCP5三个关键基因在植物器官生长中的作用奠定基础，并为深入解析植物器官发育的时空调节机理提供帮助。我们同时还希望这些理论能有助于开发改良作物性状的分子工具，在实际生产中发挥用途，为社会发展做出贡献。

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