被子植物胚囊信号调控与花粉管响应的分子机制

从水生到陆生的进化过程中，被子植物产生了适应新环境的结构、生理变化、和繁殖方式。其中，精子失去了自主运动的能力，进化出了管粉受精机制。在被子植物中，雄配子体（花粉）通常是由两个精细胞和一个营养细胞组成的三细胞结构。营养细胞萌发形成一个单细胞的管状结构，负责把两个不能运动的精子输送到雌配子体（胚囊）完成受精，即管粉受精现象。胚囊则进化出了能够吸引和识别花粉管，以及接受两个精子的独特的七细胞结构，包含一个卵细胞、两个助细胞、三个反足细胞和一个二倍体的中央细胞。管粉受精一个核心的问题是：花粉管如何发现和定位胚囊的位置并把精细胞及时地运送到胚囊？胚囊细胞之间是如何分工协调来完成管粉受精的？本课题拟以CCG和POD1基因为切入点，通过分子遗传学、细胞生物学和蛋白组学等手段，研究中央细胞调控助细胞产生吸引花粉管信号的分子机制，并分离克隆花粉管识别胚囊信号的受体，了解花粉管对胚囊信号响应的分子机制。

During transition from ocean to land, plants evolved special structures, physiology, and reproductive mechanisms to meet the challenges of the terrestrial environment. To reproduce without water, siphonogamy was evolved in angiosperms in which a tube-like structure (pollen tube) was developed by the male gametophyte (pollen) to deliver the immotile sperm to female gametophyte (embryo sac). Meanwhile, embryo sac evolved a seven-celled structure to accomplish the tasks such as pollen tube attraction, recognition, sperm release and fertilization. A typical embryo sac contains an egg, two synergids, three antipodal cells, and a diploid central cell. The pollen tube has to navigate through the maternal tissues and yet targets precisely the embryo sac; this pollen tube guidance process involves both the male and the female gametophytes. Previously, we identified a central cell-specific gene CCG which is required for the female to attract pollen tube, and a pollen-specific gene POD1 that is required for pollen tube recognition of the female cues. Here, we propose to address the two basic questions in siphonogamy by exploring the two genes in combination with diverse molecular technologies: 1) how CCG communicates with synergids to control its production of the female attracting signal; 2) how pollen tube recognizes the attracting signals by identifying putative receptors.