Whittington Camilla M, Papenfuss Anthony T, Bansal Paramjit, Torres Allan M, Wong Emily S W, Deakin Janine E, Graves Tina, Alsop Amber, Schatzkamer Kyriena, Kremitzki Colin, Ponting Chris P, Temple-Smith Peter, Warren Wesley C, Kuchel Philip W, Belov Katherine
Faculty of Veterinary Science, University of Sydney, Sydney, New South Wales 2006, Australia.
Genome Res. 2008 Jun;18(6):986-94. doi: 10.1101/gr.7149808. Epub 2008 May 7.
When the platypus (Ornithorhynchus anatinus) was first discovered, it was thought to be a taxidermist's hoax, as it has a blend of mammalian and reptilian features. It is a most remarkable mammal, not only because it lays eggs but also because it is venomous. Rather than delivering venom through a bite, as do snakes and shrews, male platypuses have venomous spurs on each hind leg. The platypus genome sequence provides a unique opportunity to unravel the evolutionary history of many of these interesting features. While searching the platypus genome for the sequences of antimicrobial defensin genes, we identified three Ornithorhynchus venom defensin-like peptide (OvDLP) genes, which produce the major components of platypus venom. We show that gene duplication and subsequent functional diversification of beta-defensins gave rise to these platypus OvDLPs. The OvDLP genes are located adjacent to the beta-defensins and share similar gene organization and peptide structures. Intriguingly, some species of snakes and lizards also produce venoms containing similar molecules called crotamines and crotamine-like peptides. This led us to trace the evolutionary origins of other components of platypus and reptile venom. Here we show that several venom components have evolved separately in the platypus and reptiles. Convergent evolution has repeatedly selected genes coding for proteins containing specific structural motifs as templates for venom molecules.
鸭嘴兽（Ornithorhynchus anatinus）首次被发现时，人们认为它是标本剥制师的恶作剧，因为它兼具哺乳动物和爬行动物的特征。它是一种非常独特的哺乳动物，不仅因为它产卵，还因为它有毒。与蛇和鼩鼱通过咬伤来释放毒液不同，雄性鸭嘴兽的每条后腿上都有一个毒刺。鸭嘴兽的基因组序列为揭示许多这些有趣特征的进化历史提供了独特的机会。在鸭嘴兽基因组中搜索抗菌防御素基因序列时，我们鉴定出三个鸭嘴兽毒液防御素样肽（OvDLP）基因，它们产生鸭嘴兽毒液的主要成分。我们发现β-防御素的基因复制及随后的功能多样化产生了这些鸭嘴兽OvDLP。OvDLP基因位于β-防御素附近，具有相似的基因结构和肽结构。有趣的是，一些蛇类和蜥蜴物种也产生含有类似分子（称为响尾蛇胺和响尾蛇胺样肽）的毒液。这使我们去追溯鸭嘴兽和爬行动物毒液其他成分的进化起源。在这里我们表明，几种毒液成分在鸭嘴兽和爬行动物中是独立进化的。趋同进化反复选择编码含有特定结构基序的蛋白质的基因作为毒液分子的模板。
