Biermann Christiane H, Marks Jessica A, Vilela-Silva Ana-Cristina E S, Castro Michelle O, Mourão Paulo A S
Friday Harbor Laboratories, University of Washington, Friday Harbor, WA 98250, USA.
Evol Dev. 2004 Sep-Oct;6(5):353-61. doi: 10.1111/j.1525-142X.2004.04043.x.
Spawning marine invertebrates are excellent models for studying fertilization and reproductive isolating mechanisms. To identify variation in the major steps in sea urchin gamete recognition, we studied sperm activation in three closely related sympatric Strongylocentrotus species. Sperm undergo acrosomal exocytosis upon contact with sulfated polysaccharides in the egg-jelly coat. This acrosome reaction exposes the protein bindin and is therefore a precondition for sperm binding to the egg. We found that sulfated carbohydrates from egg jelly induce the acrosome reaction species specifically in S. droebachiensis and S. pallidus. There appear to be no other significant barriers to interspecific fertilization between these two species. Other species pairs in the same genus acrosome react nonspecifically to egg jelly but exhibit species-specific sperm binding. We thus show that different cell-cell communication systems mediate mate recognition among very closely related species. By comparing sperm reactions to egg-jelly compounds from different species and genera, we identify the major structural feature of the polysaccharides required for the specific recognition by sperm: the position of the glycosidic bond of the sulfated alpha-L-fucans. We present here one of the few examples of highly specific pure-carbohydrate signal transduction. In this system, a structural change in a polysaccharide has far-reaching ecological and evolutionary consequences.
产卵的海洋无脊椎动物是研究受精和生殖隔离机制的优秀模型。为了确定海胆配子识别主要步骤中的变异，我们研究了三种亲缘关系密切的同域共生强壮海胆属物种的精子激活情况。精子与卵胶膜中的硫酸化多糖接触后会发生顶体胞吐作用。这种顶体反应会暴露结合蛋白，因此是精子与卵子结合的前提条件。我们发现，来自卵胶的硫酸化碳水化合物能特异性地诱导球海胆和苍白海胆的顶体反应。这两个物种之间似乎不存在其他显著的种间受精障碍。同一属中的其他物种对卵胶会发生非特异性的顶体反应，但表现出物种特异性的精子结合。因此，我们表明不同的细胞间通讯系统介导了亲缘关系非常密切的物种之间的配偶识别。通过比较精子对来自不同物种和属的卵胶化合物的反应，我们确定了精子特异性识别所需的多糖的主要结构特征：硫酸化α-L-岩藻聚糖糖苷键的位置。我们在此展示了高度特异性纯碳水化合物信号转导的少数例子之一。在这个系统中，多糖的结构变化具有深远的生态和进化后果。
