Evolutionary Biological Studies of Morphological Bipolarization in Conjugating Gametes

配子接合形态双极化的进化生物学研究

基本信息

批准号：
17370087
负责人：
NOZAKI Hisayoshi
金额：
$ 7.33万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2007
项目状态：
已结题

项目摘要

Eukaryotic sex was initially isogametic and it is assumed that anisogamy/oogamy evolved independently in many lineages including animals, land plants and volvocine green algae. The exact evolutionary mechanisms that were responsible for the evolution of oogamy from isogamy were poorly understood. In the present study, we introduced the use of molecular-genetic data in elucidating the evolutionary origin of oogamy from isogamy in the colonial volvocacean Pleodorina starrii (Nozaki et al. 2006, Cuff. Biology). In the close relative Chlamydomonas reinhardtii, sexual reproduction is isogametic with mating-types plus and minus. Mating type minus represents a "dominant sex" because the MID ("minus-dominance") gene of C. reinhardtii is both necessary and sufficient to cause the cells to differentiate as isogametes of the minus mating type. No sex-specific genes had been identified in the volvocine green algae until we successfully cloned the MID gene of P. starrii. This "OTOKOGI" (PlestMID) gene is present only in the male genome, and encodes a protein localized abundantly in the nuclei of mature sperm. Thus, P. starrii maleness evolved from the dominant sex (mating type minus) of its isogamous ancestor. The male-specific gene "OTOKOGI", first identified in this study, provides a powerful first step toward cloning the male mating type locus and determining its gene composition. Comparison of other mating type-linked loci between Chlamydomonas and Pleodorina may reveal which other genes have been important in the evolution of volvocacean "maleness." Studies of such evolved genes should shed light on the mechanisms underlying the evolution of male and female gametes that are differentiated in size and motility.

真核性别最初是异g式的，假定各种谱系在包括动物，陆地植物和沃尔沃辛绿藻类在内的许多谱系中独立演变。众所周知，造成异构情绪进化的确切进化机制。在本研究中，我们介绍了分子遗传学数据在阐明异层型卵菌的进化起源中的使用（Nozaki etal。2006，Cuff。生物学）。在亲密的相对衣原体中，有性繁殖是偶像的，配以交配型和减去。交配类型减去代表一种“主要性别”，因为C. renhardtii的Mid（减去占主导地位”基因是必要且足够的，足以使细胞与减去交配类型的异构体分化。直到我们成功克隆了Starrii的中间基因，在Volvocine绿色藻类中未发现性别特异性基因。该“ otokogi”（plestmid）基因仅存在于男性基因组中，并编码成熟精子核中局部局部局部的蛋白质。因此，P。starrii的男性气质是从其异构祖先的主要性别（交配型负）演变而来的。在这项研究中首次鉴定的男性特异性基因“ Otokogi”为克隆男性交配类型基因座并确定其基因组成提供了有力的第一步。衣原体和胸膜中其他交配类型的基因座的比较可能揭示了哪些基因在Volvocacean“ Malesentes”的进化中很重要。对这种进化基因的研究应阐明男性和女配子在大小和运动方面有分化的基础机制。