Haemocyanins constitute a group of copper‐containing respiratory proteins, and hexamerins were derived from hexapod haemocyanin but lost the ability to transport oxygen and serve as storage proteins. Although hexamerins have been reported in most insect species, none of them has been identified in Collembola, one of the most primitive hexapod lineages, thereby preventing us from exploring relevant evolutionary scenarios regarding the origin and evolution of hexamerins in hexapods. Here we report on collembolan hexamerins for the first time, and investigated the temporal expression profiles of hexamerin and haemocyanin in the collembolan Folsomia candida. Haemocyanin was expressed over the entire life cycle, with higher expression at the embryonic stage than at other stages, whereas hexamerin expression was restricted to embryos, unlike insect hexamerins, which are generally expressed from larval to adult stages. A phylogenetic analysis and molecular clock estimation suggested that all investigated hexapod hexamerins have a single and ancient origin (~423 Ma), coincident with the rise of atmospheric oxygen levels in the Silurian–Devonian period, indicating a physiological link between molecular evolution and Palaeozoic oxygen changes.

中文翻译：

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念珠菌中的六聚体和血蓝蛋白的发育表达和进化。

血蓝蛋白构成一组含铜的呼吸蛋白，六聚体衍生自六足血红蛋白，但丧失了转运氧气的功能并充当存储蛋白。尽管在大多数昆虫物种中都已报道了六聚体，但在最原始的六足动物谱系之一Collembola中都没有发现六聚体，因此阻止了我们探索有关六足动物中六聚体的起源和进化的相关进化场景。在这里，我们首次报道了collembolan六聚体，并调查了collembolan念珠菌中六聚体和血红素的时间表达谱。。血红素在整个生命周期中表达，在胚胎阶段的表达高于其他阶段，而六聚体的表达仅限于胚胎，与昆虫六聚体不同，后者通常从幼虫到成年期表达。系统发育分析和分子钟估计表明，所有研究的六足六聚体素都有一个古老的起源（〜423 Ma），与志留纪-德文统时期大气氧水平的上升相吻合，表明分子进化与古生代氧之间存在生理联系变化。