Applied Molecular Biosciences Unit (UCIBIO), Departamento de Ciências da Vida, Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa, 2829-516 Caparica, Portugal.
Toxins (Basel). 2021 Jan 28;13(2):97. doi: 10.3390/toxins13020097.
The growing number of known venomous marine invertebrates indicates that chemical warfare plays an important role in adapting to diversified ecological niches, even though it remains unclear how toxins fit into the evolutionary history of these animals. Our case study, the Polychaeta sp., is an intertidal predator that secretes toxins. Whole-transcriptome sequencing revealed proteinaceous toxins secreted by cells in the proboscis and delivered by mucus. Toxins and accompanying enzymes promote permeabilization, coagulation impairment and the blocking of the neuromuscular activity of prey upon which the worm feeds by sucking pieces of live flesh. The main neurotoxins ("phyllotoxins") were found to be cysteine-rich proteins, a class of substances ubiquitous among venomous animals. Some toxins were phylogenetically related to Polychaeta, Mollusca or more ancient groups, such as Cnidaria. Some toxins may have evolved from non-toxin homologs that were recruited without the reduction in molecular mass and increased specificity of other invertebrate toxins. By analyzing the phylogeny of toxin mixtures, we show that Polychaeta is uniquely positioned in the evolution of animal venoms. Indeed, the phylogenetic models of mixed or individual toxins do not follow the expected eumetazoan tree-of-life and highlight that the recruitment of gene products for a role in venom systems is complex.
已知有毒海洋无脊椎动物的数量不断增加，这表明化学战在适应多样化的生态位方面发挥着重要作用，尽管毒素如何适应这些动物的进化史仍不清楚。我们的案例研究，多毛类 sp.，是一种分泌毒素的潮间带捕食者。全转录组测序揭示了由吻部细胞分泌并通过粘液传递的蛋白质毒素。毒素和伴随的酶促进渗透、凝血障碍和阻止蠕虫通过吮吸活体肉块来喂养的猎物的神经肌肉活动。发现主要的神经毒素（“叶毒素”）是富含半胱氨酸的蛋白质，这是一类在有毒动物中普遍存在的物质。一些毒素在系统发育上与多毛类、软体动物或更古老的群体（如刺胞动物）有关。一些毒素可能是从非毒素同源物进化而来的，这些同源物在不减少分子质量和增加其他无脊椎动物毒素特异性的情况下被招募。通过分析毒素混合物的系统发育，我们表明多毛类在动物毒液的进化中具有独特的地位。事实上，混合或单个毒素的系统发育模型不符合预期的后生动物生命之树，并且强调了用于毒液系统的基因产物的招募是复杂的。
