Alistair Reid Venom Research Unit, Liverpool School of Tropical Medicine, Liverpool, UK.
Nat Commun. 2012;3:1066. doi: 10.1038/ncomms2065.
Phylogenetic analyses of toxin gene families have revolutionised our understanding of the origin and evolution of reptile venoms, leading to the current hypothesis that venom evolved once in squamate reptiles. However, because of a lack of homologous squamate non-toxin sequences, these conclusions rely on the implicit assumption that recruitments of protein families into venom are both rare and irreversible. Here we use sequences of homologous non-toxin proteins from two snake species to test these assumptions. Phylogenetic and ancestral-state analyses revealed frequent nesting of 'physiological' proteins within venom toxin clades, suggesting early ancestral recruitment into venom followed by reverse recruitment of toxins back to physiological roles. These results provide evidence that protein recruitment into venoms from physiological functions is not a one-way process, but dynamic, with reversal of function and/or co-expression of toxins in different tissues. This requires a major reassessment of our previous understanding of how animal venoms evolve.
毒素基因家族的系统发育分析极大地改变了我们对爬行动物毒液的起源和进化的认识，导致目前的假设认为毒液在有鳞目爬行动物中进化了一次。然而，由于缺乏同源的有鳞目非毒素序列，这些结论依赖于一个隐含的假设，即蛋白家族向毒液中的招募既罕见又不可逆转。在这里，我们使用两种蛇物种的同源非毒素蛋白序列来检验这些假设。系统发育和祖先状态分析显示，“生理”蛋白经常嵌套在毒液毒素进化枝内，这表明早期祖先被招募进入毒液，然后毒素被反向招募回到生理作用。这些结果提供了证据，表明蛋白从生理功能向毒液的招募不是一个单向过程，而是动态的，具有功能的逆转和/或毒素在不同组织中的共表达。这需要对我们以前关于动物毒液如何进化的理解进行重大重新评估。
