Centre for Snakebite Research and Interventions, Liverpool School of Tropical Medicine, Liverpool L3 5QA, UK.
Collaborative Mass Spectrometry Innovation Center, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA 92093, USA.
Science. 2021 Jan 22;371(6527):386-390. doi: 10.1126/science.abb9303.
Convergent evolution provides insights into the selective drivers underlying evolutionary change. Snake venoms, with a direct genetic basis and clearly defined functional phenotype, provide a model system for exploring the repeated evolution of adaptations. While snakes use venom primarily for predation, and venom composition often reflects diet specificity, three lineages of cobras have independently evolved the ability to spit venom at adversaries. Using gene, protein, and functional analyses, we show that the three spitting lineages possess venoms characterized by an up-regulation of phospholipase A (PLA) toxins, which potentiate the action of preexisting venom cytotoxins to activate mammalian sensory neurons and cause enhanced pain. These repeated independent changes provide a fascinating example of convergent evolution across multiple phenotypic levels driven by selection for defense.
趋同进化为理解进化变化的选择驱动因素提供了线索。蛇毒具有直接的遗传基础和明确的功能表型，为探索适应性的重复进化提供了一个模型系统。虽然蛇类主要将毒液用于捕食，并且毒液成分通常反映了饮食的特异性，但眼镜蛇的三个谱系已经独立进化出了向对手喷射毒液的能力。通过基因、蛋白质和功能分析，我们发现这三个喷射谱系拥有的毒液具有上调磷脂酶 A (PLA) 毒素的特征，这增强了预先存在的毒液细胞毒素的作用，激活哺乳动物感觉神经元并导致疼痛加剧。这些重复的独立变化提供了一个引人入胜的例子，说明了在防御选择的驱动下，跨越多个表型水平的趋同进化。
