Molecular mechanisms underlying self-sterility in the ascidians

海鞘配子是同种异体识别的典型例子，到目前为止，人们对海鞘配子自交不育的分子机制知之甚少。然而，一种被称为“接触反应”的同种异体相互作用在罗氏盐藻的血细胞中得到了很好的建立。假设配子和血细胞中的同种识别分子是相同的或密切相关的，我们在海鞘的配子和血细胞中寻找这样的分子。本项目的主要发现如下：1)空泡细胞在接触反应中分泌酚氧化酶，这使我们能够建立接触反应的定量分析。2)空泡细胞表达一种异源分子(S)及其受体，3)附着在卵黄膜上的卵泡细胞表达一种异源分子(S)。4)克隆了精子α-L岩藻糖苷酶基因，并对其进行了部分测序。5)从卵黄膜中分离出一个70 kDa的精子受体糖蛋白，并对其进行了部分测序。6)在高镁离子浓度下，配子自育；2&gt；-或咖啡因-海水。

Little is so far known on the molecular mechanisms underlying self-sterility in the ascidian gametes, a typical example of the allogeneic recognition. However, an allogeneic interaction named "contact reaction" is well established in the hemocytes of the ascidian, Halocynthia roretzi. On an assumption that allo-recognition molecules in gametes and those in hemocytes are the same or closely related, we searched for such molecules in the gametes and hemocytes of the ascidian. Major findings in this project are itemized as follows.1) Vacuolate cells secreted phenol oxidase upon contact reaction, which allowed us to develop a quantitative assay for the contact reaction.2) Vacuolated cells expressed an allo-molecule (s) and its receptor, whereas granular cells did not express such a molecule in a way to be recognized by vacuolated cells.3) Follicle cells attaching to the vitelline coat expressed an allo-molecule (s).4) cDNA of sperm alpha-L-fucosidase that mediates sperm binding to the vitelline coat was cloned and partially sequenced.5) A putative sperm-receptor glycoprotein of 70 kDa was isolated from the vitelline coat and partially sequenced.6) The gametes became self-fertile in high Mg^<2+>-or caffeine-seawater.