How do chemically defended animals resist their own toxins? This intriguing question on the concept of autotoxicity is at the heart of how species interactions evolve. In this issue of Molecular Ecology (Molecular Ecology, 2024, 33), Bodawatta and colleagues report on how Papua New Guinean birds coopted deadly neurotoxins to create lethal mantles that protect against predators and parasites. Combining chemical screening of the plumage of a diverse collection of passerine birds with genome sequencing, the researchers unlocked a deeper understanding of how some birds sequester deadly batrachotoxin (BTX) from their food without poisoning themselves. They identified that birds impervious to BTX bear amino acid substitutions in the toxin-binding site of the voltage-gated sodium channel Nav1.4, whose function is essential for proper contraction and relaxation of vertebrate muscles. Comparative genetic and molecular docking analyses show that several of the substitutions associated with insensitivity to BTX may have become prevalent among toxic birds through positive selection. Intriguingly, poison dart frogs that also co-opted BTX in their lethal mantles were found to harbour similar toxin insensitivity substitutions in their Nav1.4 channels. Taken together, this sets up a powerful model system for studying the mechanisms behind convergent molecular evolution and how it may drive biological diversity.

中文翻译：

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触摸有毒：鸫鸟和箭毒蛙致命外套膜的构成

化学防护动物如何抵抗自身的毒素？这个关于自毒性概念的有趣问题是物种相互作用如何进化的核心。在本期《分子生态学》中（分子生态学，2024 年，第 33 期），Bodawatta 及其同事报告了巴布亚新几内亚鸟类如何利用致命的神经毒素来创造致命的外套膜，以抵御捕食者和寄生虫。研究人员将多种雀形目鸟类羽毛的化学筛选与基因组测序相结合，更深入地了解了一些鸟类如何从食物中吸收致命的蝙蝠毒素（BTX）而不毒害自己。他们发现，不受 BTX 影响的鸟类在电压门控钠通道 Nav1.4 的毒素结合位点上有氨基酸取代，该通道的功能对于脊椎动物肌肉的正常收缩和松弛至关重要。比较遗传和分子对接分析表明，一些与对 BTX 不敏感相关的取代可能通过正选择在有毒鸟类中普遍存在。有趣的是，在毒箭蛙的致命外套膜中也加入了 BTX，我们发现它们的 Nav1.4 通道中也存在类似的毒素不敏感替代。总而言之，这建立了一个强大的模型系统，用于研究趋同分子进化背后的机制及其如何驱动生物多样性。