Allorecognition mechanisms during ascidian fertilization
Allorecognition mechanisms during ascidian fertilization
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DOI：
10.1387/ijdb.072544yh
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发表时间：
2008-01-01
影响因子：
0.7
通讯作者：
Sawada, Hitoshi
中科院分区：
文献类型：
--
作者：
Harada, Yoshito;Sawada, Hitoshi
海鞘（原始脊索动物）是雌雄同体动物，几乎同时释放精子和卵子。但是，许多海鞘，包括海鞘和海藻，表现出自体不育或偏好异体受精而不是自体受精。这种同种异体识别过程背后的分子机制目前还知之甚少。我们最近通过定位克隆鉴定了肠弯曲菌中导致自交不亲和的基因：精子携带的多囊蛋白1样受体（称为s-Themis）及其卵黄膜（VC）上的纤维蛋白原样配体（称为v-Themis）具有高度多态性，似乎与弯曲杆菌受精过程中的同种异体识别有关。另一方面，在 H. roretzi 中，我们发现 HrVC70 是 VC 的 70 kDa 主要成分，由 12 个表皮生长因子 (EGF) 样重复组成，是一种候选的同种异体识别蛋白，因为该蛋白在卵母细胞成熟过程中与 VC 的附着以及弱酸的分离分别与自体不育的获得和丧失密切相关，而且还因为非自体精子而不是自体精子与 HrVC70-琼脂糖有效结合。作为 HrVC70 的结合伴侣，精子脂筏中的 35 kDa GPI 锚定糖蛋白（称为 HrUrabin）被鉴定出来：HrUrabin 似乎在受精过程中同种可识别精子与 HrVC70 结合中发挥着关键作用。在本综述中，我们通过考虑包括真菌和开花植物在内的另一种生物体中的 SI 系统，描述了海鞘受精过程中同种异体识别或自交不亲和的分子基础的当前进展。
Ascidians (primitive chordates) are hermaphroditic animals, releasing sperm and eggs nearly simultaneously. But, many ascidians, including Ciona intestinalis and Halocynthia roretzi, show self-sterility or preference for cross-fertilization rather than self-fertilization. The molecular mechanisms underlying this allorecognition process are only poorly understood. We recently identified the genes responsible for self-incompatibility in C. intestinalis by a positional cloning: sperm-borne polycystin 1-like receptor, referred to as s-Themis, and its fibrinogen-like ligand called v-Themis on the vitelline coat (VC) are highly polymorphic and appear to be responsible for allorecognition in the fertilization of C. intestinalis. In H. roretzi, on the other hand, we revealed that HrVC70, a 70-kDa main component of the VC consisting of 12 epidermal-growth-factor (EGF)-like repeats, is a candidate allorecognition protein, since the attachment of this protein to the VC during oocyte maturation and its detachment by weak acid are closely linked to the gain and the loss of self-sterility, respectively, and also since nonself-sperm rather than self-sperm efficiently bound to HrVC70-agarose. As a binding partner of HrVC70, a 35-kDa GPI-anchored glycoprotein in sperm lipid rafts, referred to as HrUrabin, was identified: HrUrabin appears to play a key role in allorecognizable sperm binding to HrVC70 during fertilization. In the present review, we describe the current progress on the molecular bases of allorecognition, or self-incompatibility, during ascidian fertilization, by considering the SI systems in another organisms including fungies and flowering plants.