Members of the phylum Arthropoda, comprising over 80% of total animal species, have evolved regenerative abilities, but little is known about the molecular mechanisms mediating this process. Transforming growth factor β (TGF‐β) signaling mediates a diverse set of essential processes in animals and is a good candidate pathway for regulation of regeneration in arthropods. In this study we investigated the role of activin signaling, a TGF‐β superfamily pathway, in limb regeneration in the crayfish. We identified and cloned a downstream transcription factor in the activin pathway, Smox, and characterized its function with regard to other elements of the activin signaling pathway. Gene knockdown of Smox by RNAi induced regeneration of complete but smaller pereopods after autotomy. This indicates that activin signaling via Smox functions in regulation of pereopod growth and size. The expression levels of both Smox and the activin receptor babo were closely correlated with molting. The expression level of Smox increased when babo was knocked down by RNAi, indicating that Smox and babo transcription are linked. Our study suggests that the Babo‐Smox system in activin signaling is conserved in decapods, and supports an evolutionary conservation of this aspect of molecular signaling during regeneration between protostomes and deuterostomes.

中文翻译：

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活化素信号转导因子Smox是小龙虾截肢后再生期间附件大小的重要调节剂。

节肢动物门的成员具有超过80％的总动物物种，具有进化能力，但对介导该过程的分子机制知之甚少。转化生长因子β（TGF-β）信号传导介导动物中多种多样的基本过程，并且是节肢动物再生调节的良好候选途径。在这项研究中，我们研究了激活素信号传导（一种TGF-β超家族途径）在小龙虾肢体再生中的作用。我们在激活素途径Smox中鉴定并克隆了一个下游转录因子，并针对激活素信号传导途径的其他元素表征了其功能。Smox的基因敲低通过RNAi诱导的完整的但较小的骨脚切开后再生。这表明激活蛋白通过Smox信号传导在调节骨足生长和大小中起作用。Smox和激活素受体babo的表达水平与蜕皮密切相关。当RNAi敲除babo时，Smox的表达水平增加，表明Smox和babo转录是相关的。我们的研究表明，激活素信号传导中的Babo-Smox系统在十足动物中是保守的，并支持在原虫和氘核之间再生期间分子信号这方面的进化保守性。