FHY3介导的拟南芥花发育的网络解析

Floral stem cells are responsible for producing a defined number of floral organs, and then will be terminated programmatically at a particular developmental stage. Therefore, floral stem cells offer an ideal model to study the temporal control of stem cells maintenance, which is also very significant for the high-yielding of crops. In Arabidopsis floral meristem, WUSCHEL is a key gene for stem cells maintenance; AGAMOUS and other essential genes can repress stem cells maintenance by temporal control of WUSCHEL expression, however, the involved genes and molecular mechanism of this process is still not very clear. Based on an AG weak mutant ag-10 EMS mutagenesis, we screened a mutant with enhanced froral meristem indeterminacy of ag-10. Using map based cloning we detected a premature mutant occurring in FHY3 coding region; transgenic plant with over-expression of this gene and allele analysis show rescued or enhanced phenotype respectively, which suggested the mutation was responsible for mutant defect; in situ hybridization assay show the WUSCHEL expression was delayed due to the loss of function of FHY3.In this study, we will study the function of FHY3 and figure out the FHY3 target genes and their function in stem cells maintenance and determinacy by using a combinational approach of genetics , next generation sequencing and bioinformatics , our goal is to reveal the FHY3 mediated molecular net work in floral development, especially in floral meristem maintenance and determinacy.

植物花干细胞负责产生特定数目的花器官后其干细胞活性被程序性终止，因此花干细胞是研究干细胞时序性调控的理想模型，同时对其调控机理的研究对作物高产也具有重要意义。在拟南芥的花分生组织中，WUSCHEL是调控花干细胞活性的关键基因；AGAMOUS和其它基因可通过时序性调控WUSCHEL的表达而抑制干细胞的活性，参与该过程的基因及分子机制还不很清楚。我们前期工作中利用一个AGAMOUS弱突变体ag-10，通过EMS诱变，筛选出一个花干细胞活性增强的突变体。图位克隆表明FHY3基因发生了终止突变，转基因恢复和等位基因验证表明该基因参与了花干细胞活性的调控；原位杂交证明该基因可调控WUS的表达。本研究将通过遗传学及高通量测序等多种分子生物学技术来研究FHY3在花干细胞维持和分化中的作用机制，最终通过FHY3靶基因的鉴定及功能分析揭示FHY3介导的花发育及干细胞分化的分子网络体系。

植物所有组织器官均来源于分生组织/干细胞。花序分生组织是一个维持和分化的过程。当所有的花器官的原基由花干细胞产生后，花干细胞就要被及时终止。转录因子FHY3是光信号转导中关键基因，且通过转录激活作用调控植物的营养生长。在本研究中我们发现FHY3在花序分生组织的分化及茎顶端分生组织的维持中起着重要。利用全基因组ChIP-seq和RNA-seq技术，我们鉴定出在FHY3花序中的几百个靶基因，且FHY3对它们具有转录抑制作用；其中CLAVATA3 (CLV3), SEPALLATA1 (SEP1), and SEP2 均是FHY3的靶基因。在fhy3 ag-10背景下超表达SEP2能部分削弱其增强的分生组织活性表型。在茎顶端分生组织，FHY3能够直接抑制CLV3从而调控WUS来影响干细胞活性。在花序分生组织中，FHY3抑制CLV3但激活SEP2来促使花序分生组织的终止。光抑制CLV3的表达，但在fhy3,phytochrome B 突变体背景下CLV3对光不敏感，暗示FHY3参与了光调控分生组织活性的生物过程。我们的结果揭示了FHY3在花分生组织维持和分化中的分子机理，阐明了转录因子在不同的器官和发育进程中功能的不同。

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