植物的有性生殖产生种子及果实，而受精过程是完成植物有性生殖的关键。其中，花粉与雌蕊的相互识别是受精的前提和保障。被子植物的精子丧失了游动能力，需要雄配子体产生的花粉管将精细胞运送到雌蕊内的胚囊完成受精。雌蕊为花粉管的生长提供营养和吸引信号，这方面已有较多了解。然而花粉管感受并响应这些雌蕊信号进行导向性生长的分子机理还不清楚。我们近期发现拟南芥MDP定位于花粉管顶端质膜外层，其突变体表现出配子体雄性不育。我们初步的研究结果表明MDP突变破坏了花粉管感受并响应雌蕊信号而进行导向性生长的能力，暗示MDP可能作为花粉管受体直接参与识别雌蕊信号。本项目将综合使用细胞和分子生物学、正反向遗传学、药剂细胞学等方法，对MDP在花粉管与雌蕊识别过程中的作用及其调控的信号网络进行研究，阐明MDP参与感受和响应雌蕊信号的分子机理，加深对被子植物授粉识别这一重要过程的了解，为作物的遗传改造奠定理论基础。

Double fertilization of flowering plants has been a fascinating research area for over a century, a process in which two immotile sperm cells carried within a pollen tube fertilize two female gametes, the egg and the central cell, to form embryo and endosperm respectively. It is a tightly controlled process involving constant and precise communications between pollen tubes and female tissues. It is well known that female tissues provide nutrients and guidance cues to support polar and directional tube growth. But little is known on sensors of pollen tubes that perceive female cues to initiate cellular activities,leading to directional growth. We show that Arabidopsis MDP (Male Determinant of Pollination) is a member of COBRA family encoding glycosylphosphatidylinositol-anchored proteins (GAPs). Pollen tubes defective in MDP could not respond to female cues, leading to male gamtophytic sterility. We propose to study the molecular mechanisms underlying MDP-regulated pollen tube-pistil recognition. Furthermore, GAPs exist in large numbers in eukaroytes. Although a few GAPs were reported by mutational studies in plants, there is hardly any information regarding their processing, subcellular localization and genetic networks in which they function. Therefore, we plan to use MDP to explore these neglected but critical aspects. Knowledge gained from this study will not only provide a better understanding of signaling networks regulating pollen tube-pistil recognition but also provide a case study for a large number of functional unknown GAPs in plants.