HAP2/GCS1: Mechanisms of Double Fertilization

受精是所有有性生物生命周期中的中心事件，发生在雄性和雌性配子融合的时候。开花植物（包括玉米、水稻和大豆等主要作物）经历双重受精：一个精子与卵细胞融合形成胚胎，另一个精子与中心细胞融合产生胚乳，胚乳是一种为胚胎提供代谢支持的特殊组织。这些事件导致了种子的形成，这是人类饮食的基础。在任何生物体中，负责配子融合的分子机制都没有得到很好的理解。在拟南芥中，hap2突变完全阻断了精子使雌性配子受精的能力，而拟南芥是一种极好的遗传模式生物。HAP2基因编码一种蛋白，这种蛋白只在精子细胞中表达，预计会跨越精子质膜。该项目的假设是，精子表面的HAP2蛋白与雌性配子上的另一种蛋白相互作用，这种相互作用是配子融合所必需的。本文提出的实验旨在确定HAP2在受精中的作用，确定HAP2在精子膜上的拓扑结构，鉴定与HAP2相互作用的卵子和中央细胞表达蛋白，并确定对HAP2功能至关重要的HAP2序列。这些研究有可能揭示包括人类在内的许多生物中受精的关键分子机制。该项目将为布朗大学和罗德岛社区学院招收的一名研究生和几名本科生提供跨学科培训。此外，还将编制新的教材和实验练习，分发给教育工作者。

Fertilization is the central event in the life cycle of all sexual organisms and occurs when male and female gametes fuse. Flowering plants (including major crops like corn, rice, and soybean) undergo double fertilization: one sperm fuses with the egg cell to form an embryo and another sperm fuses with the central cell to produce endosperm, a specialized tissue that provides metabolic support for the embryo. These events lead to formation of seeds, the basis of the human diet. The molecular mechanisms responsible for the fusion of gametes are not well understood in any organism. The hap2 mutation completely blocks the ability of sperm to fertilize female gametes in Arabidopsis thaliana, a flowering plant that is an excellent genetic model organism. The HAP2 gene encodes a protein that is only expressed in sperm cells and is predicted to span the sperm plasma membrane. The hypothesis of this project is that the HAP2 protein on the sperm surface interacts with another protein on the female gamete and that this interaction is required for gamete fusion. The experiments proposed here are designed to define the role of HAP2 in fertilization, determine the topology of HAP2 on sperm membranes, identify egg and central cell-expressed proteins that interact with HAP2 and define HAP2 sequences that are critical for its function. These studies have the potential to uncover molecular mechanisms critical for fertilization in many organisms including humans. This project will provide interdisciplinary training for a graduate student and several undergraduates recruited from Brown University and The Community College of Rhode Island. In addition, novel educational materials and laboratory exercises will be developed and distributed to educators.