YUCCA2和YUCCA6调控拟南芥雄配子第一次有丝分裂的机理研究

The male germline is segregated through an asymmetric cell division named pollen mitosis I/PMI of the haploid microspore. As one of the most important hormone in plants, auxin plays roles in almost all processes of plant development. Nevertheless, the detailed function and molecular mechanisms of auxin during PMI remains elusive. Our previous studies have shown that the male gametophyte development in yuc2yuc6 is arrested prior to PMI. Through detailed analyses, we also found that arf6arf8 and arf17 display similar phenotypes as yuc2yuc6 during the microspore development, suggesting these auxin response factors may regulated by YUC2, 6 proteins and involved in the regulation of PMI process. This proposed project will analyze the expression pattern of YUC2 and 6 in anther and determine the distribution of auxin in yuc2yuc6 anther; investigate the role of YUC2 and 6 at specific stages of PMI; discover and confirm the YUC2/6-ARF6/8/17 pathway. By studying this project, we expect to clarify the functions of the YUC2/6 mediated auxin pathway in PMI process, and to broaden our knowledge about the regulatory mechanisms governing plant reproduction.

花粉第一次有丝分裂（PMⅠ）是植物雄配子发育的关键步骤，小孢子经过PMⅠ形成生殖细胞。作为植物体内最重要的激素之一，生长素在PMⅠ过程的功能并不清楚。本项目前期的研究发现生长素合成酶缺失的突变体yuc2yuc6中小孢子的发育被阻滞在PMⅠ之前的阶段。同时，我们通过筛选发现arf6arf8和arf17小孢子的发育缺陷与yuc2yuc6较为一致，暗示这三个生长素响应因子很可能受到YUC2，6蛋白的调控参与PMⅠ过程。本项目将分析YUC2，6蛋白在花药中的表达谱以及它们对花药生长素分布的影响；更深入地探索YUC2，6在PMⅠ中发挥功能的具体阶段；验证ARF6/8/17是否受YUC2，6蛋白调控；筛选受YUC2/6-ARF6/8/17途径调控的下游基因。期望通过本项目的研究，阐明YUC2与YUC6所介导的生长素途径在雄配子PMⅠ中的功能，拓宽人们对植物生殖过程调控网络与调控机制的认识。

雄配子发育是植物生殖发育的基本过程，第一次有丝分裂（PMI）是雄配子发育的早期事件。虽然目前的研究已经发现生长素在生殖发育中发挥作用，但是其在雄配子发育特别是PMI中的功能及其下游的信号通路并不清楚。本项目的研究结果显示YUC2与YUC6是花药中主要的生长素合成酶。yuc2yuc6双突变的小孢子发育阻滞在PMI之前，导致yuc2yuc6无法产生正常花粉。同时我们通过DII-VENUS系统检测了花粉中生长素的积累，发现生长素丰富积累于单核时期的花粉中。这些结果说明YUC2与YUC6合成的生长素确实积累于单核花粉，并对促进单核花粉经PMI形成双核花粉是必需的。为了探索生长素调控花粉发育的信号通路，我们筛选了一系列的arf突变体，发现arf17 花粉的发育缺陷与yuc2yuc6相似，也是阻滞在PMI之前。同时，通过芯片分析及比对我们发现yuc2yuc6与arf17花序中下调的基因有大部分的重叠，暗示ARF17可能在YUC2和YUC6下游发挥功能参与花粉发育。这些研究结果首次揭示了生长素在花粉发育过程的具体功能及可能的信号通路。