Molecular mechanisms underlying self-sterility in the ascidians

海鞘配子是一种典型的同种异体识别，其自育性的分子机制目前尚不清楚。然而，一种被称为“接触反应”的异体相互作用在海鞘（Halocynthia roretzi）的血细胞中得到了很好的证实。假设配子中的同种异体识别分子与血细胞中的同种异体识别分子相同或密切相关，我们在海鞘的配子和血细胞中寻找同种异体识别分子。本项目的主要发现如下：1)液泡细胞在接触反应时分泌酚氧化酶，这使我们能够对接触反应进行定量分析。2)空泡细胞表达同种异体分子及其受体，而颗粒细胞不表达这种分子，而这种分子不能被空泡细胞识别。4)克隆了介导精子与卵磷脂被结合的精子α - l -聚焦酶cDNA，并对其进行了部分测序。5)从卵黄皮中分离到一个约70 kDa的精子受体糖蛋白，并对其进行了部分测序。6)配子在高Mg^<2+>-或咖啡因-海水中可以自育。

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.