摘要
Proteins involved in sexual reproduction are known to evolve rapidly, often as the result of positive Darwinian selection, although the selective forces driving such adaptive changes are poorly understood. A process of coevolution between proteins in male and female gametes may promote rapid divergence of fertilization proteins. In the mouse, only two proteins have been shown so far to be essential for sperm-egg fusion, IZUMO1 in the sperm cell and CD9 in the egg. The role of these proteins has not been fully elucidated, and it has been suggested that they may act as fusogens, interacting in trans with proteins on the other cell, or regulators of fusogens through cis interactions. Here we analyze the evolution of IZUMO1 and CD9 in a group of rodent species. To assess possible protein interactions between IZUMO1 and CD9, we examined potential coevolution based on analyses of correlated evolutionary rates. We found evidence that both proteins evolve adaptively, with a more intense signal of positive selection in IZUMO1. In addition, our findings suggest that these proteins may have some form of interaction, although they have not been regarded as fusogens interacting directly with each other. The adaptive divergence of IZUMO1 and CD9 could influence reproductive compatibility, and, thus, these proteins may participate in the establishment of specific sperm-egg recognition systems. Further studies are required to uncover the role of IZUMO1 and CD9 during gamete fusion in order to understand the molecular basis of their coevolution, as other selective forces could also lead to general signatures of coevolution.
摘要译文
众所周知，涉及性繁殖的蛋白质可以迅速发展，虽然达到达尔文选择的结果，但是驾驶这种适应性变化的选择性很难理解。雄性和雌性配子中蛋白质之间的共同进程可以促进施肥蛋白的快速分歧。在小鼠中，迄今已仅显示两种蛋白质对于精子蛋融合，Izumo1在精子细胞和CD9中必需的。这些蛋白质的作用尚未完全阐明，并且已经提出它们可以作为Fusogens作用，在其他细胞上与蛋白质相互作用，或通过顺应相互作用的Fusogens的调节剂。在这里，我们分析了一组啮齿动物物种中Izumo1和CD9的演变。为了评估Izumo1和CD9之间可能的蛋白质相互作用，我们基于相关进化率的分析检查了潜在的共乐。我们发现，两种蛋白质的证据表明，在Izumo1中具有更强烈的阳性选择信号。此外，我们的研究结果表明，这些蛋白质可能具有某种形式的相互作用，尽管它们未被被认为是彼此直接相互作用的Fusogens。 Izumo1和CD9的自适应分歧可以影响生殖相容性，因此这些蛋白质可以参与建立特定的精子蛋识别系统。需要进一步的研究来揭示在配子融合期间Izumo1和CD9的作用，以便理解其参与的分子基础，因为其他选择性也可能导致参数的一般签名。
Alberto Vicens; Eduardo R.S. Roldan[*];. Coevolution of Positively Selected IZUMO1 and CD9 in Rodents: Evidence of Interaction Between Gamete Fusion Proteins?1[J]. Biology of Reproduction, 1990,90(5)