MYB53与miR156-SPL途径互作调控拟南芥开花的分子机理研究

Flowering time in plants is tighly controlled by flowering determination. Precise timing of vegetative-to-reproductive transition is crucial for the successful reproductive development, therefore affecting pollination, seed development, yield, and productivity in plants. A microarray analysis of genes differentially expressed in shoot apices from different developmental stages in Arabidopsis identified a transcription factor, MYB53, whose expression decreases with developmental time, exactly mimicking the temporal expression of miR156. Overexpression of MYB53 delayed flowering time, increased miR156 level, elevated the expression of miR156a, and decreased the expression of corresponding SPL3 genes. In addition, the expression patterns of MYB53, miR156a and SPL3 were partly overlapping. Based on the gene expression analysis and the mutant phenotype, we hypothesize that MYB53 may directly regulate the expression of miR156a by binding to its promoter to function in the regulation of flowering time in Arabidopsis. To confirm our hypothesis, we will analyze the relationship between MYB53 expression pattern and flowering time control, the genetic interaction between MYB53 and the miR156-SPL module, the mode of MYB53-regulated miR156 expression as well as the MYB53-regulated gene network. All these analyses will help us deeply understand the regulatory mechanism of MYB53 in the regulation of flowering time with an ultimate goal to improve plant yield and productivity.

开花决定控制植物开花时间，影响植物生育期、植物授粉及种子发育的最佳时间，从而影响作物产量和品质。申请者发现转录因子MYB53表达模式和miR156一致，都随植物年龄增长而表达量降低。过表达MYB53延迟植物开花时间，并引起miR156成熟体和前体miR156a表达量增加和SPL3下调表达。由此，推测MYB53直接调节miR156a基因表达来调控植物开花时间。为了证明此假设，以拟南芥为材料，通过分析MYB53表达模式对植物开花时间的影响，研究MYB53与miR156-SPLs信号通路及调控植物开花基因的分子与遗传关系，并探讨MYB53调控miR156表达的方式，和RNA-seq分析其调控的基因网络，以期明确MYB53与miR156-SPLs信号通路互作调控植物开花的分子机制和调控网络。本项目完成将明确MYB53调控植物开花时间的分子机理，将为作物产量提高和品种改良提供重要的理论支持。

植物胚胎后发育会经历两个生长阶段转变：从幼年向成年营养生长期的转变，和从营养期到生殖期的阶段转换（开花）。开花是有花植物生活史中一个重大转折点，是个体发育和后代繁衍的中心环节。植物开花时间的调控一直是植物发育生物学的研究热点。先前研究发现，年龄途径在植物营养生长阶段转变和开花调控中发挥重要作用。本项目中发现的MYB53基因具有年龄相关的表达模式，但是其功能依然未知。为进一步解析MYB53在开花调控中的功能，首先分析MYB53的表达模式及对植物开花时间的影响；探索MYB53与miR156-SPL-miR172通路在调控植物开花过程中的分子与遗传关系；并解析其基因调控网络和分子机制。根据项目的设计，我们基本上完成了研究目标。. 我们研究发现，MYB53表达随年龄的增加而降低，体现出昼夜节律的特征，且主要在植物茎尖和生殖器官中表达。过表达MYB53显著抑制了植物营养生长阶段转变和开花。转录组数据结果显示，过表达MYB53导致开花相关基因、昼夜节律、逆境胁迫和激素途径基因的表达显著变化；过表达MYB53还抑制了年龄途径关键微小RNA——miR172，使其靶基因SMZ的表达显著上调，并降低FT的表达；进一步的遗传证据证明，在调控植物营养生长阶段转变和开花中，miR172上位于MYB53。此外，我们还发现MYB53受miR167的调控，且MYB53反馈抑制miR167D基因的表达。本项目明确了MYB53调控植物开花时间的分子机理，将为作物产量提高和品种改良提供重要的理论支持。