Tanaka Kohtaro, Diekmann Yoan, Hazbun Alexis, Hijazi Assia, Vreede Barbara, Roch Fernando, Sucena Élio
Instituto Gulbenkian de Ciência, Oeiras, Portugal
Instituto Gulbenkian de Ciência, Oeiras, Portugal.
Mol Biol Evol. 2015 Jul;32(7):1730-47. doi: 10.1093/molbev/msv052. Epub 2015 Mar 4.
Gene families often consist of members with diverse expression domains reflecting their functions in a wide variety of tissues. However, how the expression of individual members, and thus their tissue-specific functions, diversified during the course of gene family expansion is not well understood. In this study, we approached this question through the analysis of the duplication history and transcriptional evolution of a rapidly expanding subfamily of insect Ly6 genes. We analyzed different insect genomes and identified seven Ly6 genes that have originated from a single ancestor through sequential duplication within the higher Diptera. We then determined how the original embryonic expression pattern of the founding gene diversified by characterizing its tissue-specific expression in the beetle Tribolium castaneum, the butterfly Bicyclus anynana, and the mosquito Anopheles stephensi and those of its duplicates in three higher dipteran species, representing various stages of the duplication history (Megaselia abdita, Ceratitis capitata, and Drosophila melanogaster). Our results revealed that frequent neofunctionalization episodes contributed to the increased expression breadth of this subfamily and that these events occurred after duplication and speciation events at comparable frequencies. In addition, at each duplication node, we consistently found asymmetric expression divergence. One paralog inherited most of the tissue-specificities of the founder gene, whereas the other paralog evolved drastically reduced expression domains. Our approach attests to the power of combining a well-established duplication history with a comprehensive coverage of representative species in acquiring unequivocal information about the dynamics of gene expression evolution in gene families.
基因家族通常由具有不同表达结构域的成员组成，这反映了它们在多种组织中的功能。然而，在基因家族扩张过程中，各个成员的表达，以及由此产生的组织特异性功能是如何多样化的，目前还不太清楚。在本研究中，我们通过分析昆虫Ly6基因快速扩张的亚家族的复制历史和转录进化来探讨这个问题。我们分析了不同的昆虫基因组，鉴定出七个Ly6基因，它们通过双翅目高级类群中的连续复制从单个祖先起源。然后，我们通过表征其在甲虫赤拟谷盗、蝴蝶非洲苎麻蛱蝶和蚊子斯氏按蚊中的组织特异性表达，以及在三个双翅目高级类群物种（代表复制历史的不同阶段，即微小食蚜蝇、地中海实蝇和黑腹果蝇）中其复制基因的组织特异性表达，来确定起始基因的原始胚胎表达模式是如何多样化的。我们的结果表明，频繁的新功能化事件导致了该亚家族表达广度的增加，并且这些事件在复制和物种形成事件之后以相当的频率发生。此外，在每个复制节点，我们一致发现不对称的表达分化。一个旁系同源基因继承了起始基因的大部分组织特异性，而另一个旁系同源基因则进化出大幅减少的表达结构域。我们的方法证明了将完善的复制历史与对代表性物种的全面覆盖相结合，在获取有关基因家族中基因表达进化动态的明确信息方面的强大作用。
