Expression of venom gene homologs in diverse python tissues suggests a new model for the evolution of snake venom.
Expression of venom gene homologs in diverse python tissues suggests a new model for the evolution of snake venom.
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DOI：
10.1093/molbev/msu294
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发表时间：
2015
影响因子：
10.7
通讯作者：
Jacobo Reyes-Velasco;D. Card;Audra L. Andrew;Kyle J Shaney;Richard H. Adams;Drew R. Schield;N. Casewell;S. Mackessy;T. Castoe
中科院分区：
文献类型：
--
作者：
Jacobo Reyes-Velasco;D. Card;Audra L. Andrew;Kyle J Shaney;Richard H. Adams;Drew R. Schield;N. Casewell;S. Mackessy;T. Castoe
在过去的几十年里，人们对蛇毒基因进化进行了深入的研究，但大多数以前的研究都缺乏完整的蛇基因组背景和不同蛇组织中基因表达的完整背景。我们采取了一种新的方法来研究蛇毒的进化，利用缅甸蟒蛇的完整基因组，包括基因表达的组织特异性模式的信息。我们确定了蟒蛇基因组中蛇毒基因的直系同源物，并对这些毒液同源物的基因表达进行了详细分析，以确定蛇毒基因家族与所有其他基因之间的差异模式。我们发现蟒蛇的毒液基因同源物在口腔腺外的许多不同组织中表达，这说明了仅使用转录组数据来定义“毒液毒素”的陷阱。“我们假设蟒蛇可能代表了主要毒液发育之前的祖先状态，这得到了我们发现毒液基因家族的扩展主要限于剧毒的新蛇的支持。因此，蟒蛇提供了对蛇毒系统招募基因的偏见的见解。与所有其他蟒蛇基因相比，蟒蛇毒液同源物通常以较低水平表达，在组织中具有较高的差异，并且在较少的器官中表达。我们提出了一个模型，蛇毒基因的进化中，毒液基因的招募优先从基因具有特定的表达谱特征，这有利于一个接近中性的过渡到专门的毒液系统的表达。
Snake venom gene evolution has been studied intensively over the past several decades, yet most previous studies have lacked the context of complete snake genomes and the full context of gene expression across diverse snake tissues. We took a novel approach to studying snake venom evolution by leveraging the complete genome of the Burmese python, including information from tissue-specific patterns of gene expression. We identified the orthologs of snake venom genes in the python genome, and conducted detailed analysis of gene expression of these venom homologs to identify patterns that differ between snake venom gene families and all other genes. We found that venom gene homologs in the python are expressed in many different tissues outside of oral glands, which illustrates the pitfalls of using transcriptomic data alone to define "venom toxins." We hypothesize that the python may represent an ancestral state prior to major venom development, which is supported by our finding that the expansion of venom gene families is largely restricted to highly venomous caenophidian snakes. Therefore, the python provides insight into biases in which genes were recruited for snake venom systems. Python venom homologs are generally expressed at lower levels, have higher variance among tissues, and are expressed in fewer organs compared with all other python genes. We propose a model for the evolution of snake venoms in which venom genes are recruited preferentially from genes with particular expression profile characteristics, which facilitate a nearly neutral transition toward specialized venom system expression.