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Molecular Mechanisms Underlying Self-Sterility In Ascidian Gametes

海鞘配子自不育的分子机制

基本信息

批准号：
02454021
负责人：
HOSHI Motonori
金额：
$ 3.46万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1991
项目状态：
已结题

项目摘要

The ascidians are hermaphrodite and many species are self-sterile. In the self-sterile solitary ascidian Ciona intestinalis, only heterologous, but no autologous. spermatozoa can bind to the vitelline coat (VC). It is postulated that fucosyl proteins of the VC and a- L- fucosidase of sperm mediate the binding, yet the molecules controlling allorecognition between the gametes remain unknown. In another self-sterile solitary ascidian Halocynthia roretzi. both heterologous and autologous spermatozoa bind to the VC by a similar mechanism us ing fucosy I proteins and a - L - f ucos i dase. Because the oocytes deprived of the VC are self-fertile. the autologous spermatozoa seem incapable of penetrating the VC in this species.By using in vitro fertilization assay of oocytes from Qi-Qna ovaries, we have found that self-sterility is contributed or controlled by products. presumably a glycoprotein. of the overlying follicle cells. When fully-grown ovarian oocytes with a germinal vesicle were inc … More ubated in sea water at room temperature. they underwent germinal vesicle breakdown within 20 minutes and became fertile. and eventually acquired self, -sterility within a maximum of 3 hours of incubation. When they were deprived of follicle cells by gentle shaking before incubation, most of them remained self-fertile even after 3 hours. If follicle cellfree oocytes were incubated with the free follicle cells. they became selfsterile as well as follicle cell-intact oocytes.The acquisition of self-sterility was accompanied by an ultrastructural change in the VC fixed with tannic acid : an electron-dense. thin layer appeared on the outer surface of the VC after 3 hours of incubation. This layer was similarly observed in follicle cell-free oocytes only when they had been incubated with the free follicle cells. We have purified a chymoteypsin-like protease as a VC-lysin in Ciona spermatozoa. Interestingly, the enzyme purified from Ciona spermatozoa digested the electron-dense layer.These observations suggest that, during oogenesis, follicle-cells synthesize a self-sterility controlling factor (probably a glycoprotein) which. following germinal vesicle breakdown, is secreted to coat the VC in a way that confers self-sterility to the oocytes. It is an interesting question to ask whether the allorecognition molecule (s) is contained in the outermost electrondense layer of the VC or not. Less

海鞘是雌雄同体的，许多种类是自交不育的。在自交不育的单生海鞘中，只有异源的，但没有自体的。精子可与卵黄膜（VC）结合。据推测，VC的岩藻糖基蛋白和精子的α- L-岩藻糖苷酶介导了这种结合，但控制配子之间同种识别的分子仍然未知。在另一个自我不育的孤独海鞘Halocynthia roretzi。异源和自体精子都通过岩藻糖基I蛋白和α- L -岩藻糖苷酶通过类似的机制与VC结合。因为缺乏VC的卵母细胞是自我受精的。本研究通过对Qi-Qna卵巢卵母细胞的体外受精试验，发现其自身不育性是由产品引起或控制的。推测是糖蛋白。毛囊细胞的表面。当发育成熟的卵巢卵母细胞具有生殖囊泡时， ...更多信息在室温下在海水中加热。它们在20分钟内经历生殖囊泡破裂并变得可生育。并最终在最多3小时的孵育内获得自身不育。当它们在孵育前通过轻轻摇动去除卵泡细胞时，即使在3小时后，它们中的大多数仍然保持自能生殖。卵泡细胞与游离卵母细胞共同孵育。结果表明，在用单宁酸固定的VC中，随著自身不育的获得，其超微结构发生了变化：电子密度增加。孵育3小时后，在VC的外表面上出现薄层。这一层类似地观察到卵泡细胞游离卵母细胞，只有当他们已经与自由卵泡细胞孵育。我们已经纯化的凝乳蛋白酶样蛋白酶作为VC-溶素在玻璃海鞘精子。有趣的是，从玻璃海鞘精子中纯化的酶消化电子致密层，这些观察表明，在卵子发生过程中，卵泡细胞合成一种自我不育控制因子（可能是一种糖蛋白），在生殖囊泡破裂后，以赋予卵母细胞自身不育性的方式分泌以包覆VC。这是一个有趣的问题，要问是否包含在VC的最外层电子致密层的同种识别分子（S）。少