Evolution of a complex locus: exon gain, loss and divergence at the Gr39a locus in Drosophila.
Evolution of a complex locus: exon gain, loss and divergence at the Gr39a locus in Drosophila.
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DOI：
10.1371/journal.pone.0001513
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发表时间：
2008-01-30
期刊：
影响因子：
3.7
通讯作者：
Ritchie MG
中科院分区：
文献类型：
--
作者：
Gardiner A;Barker D;Butlin RK;Jordan WC;Ritchie MG
基因家族通常通过基因复制，然后采用新的或改变的基因功能来进化。另一种进化新的相关功能的方法是选择性剪接复杂基因的现有外显子。动物的化学感受基因家族的特征在于许多相关功能的位点。选择性剪接在化学感受基因座中的报道很少，例如在黑腹果蝇的约120个基因座中的5个中。味觉受体基因Gr39a有四个大的外显子，它们与三个小的保守外显子交替剪接。最近的基因组序列的11个其他物种的果蝇已成为可用的，使我们能够检查在结构上的变化的Gr39a基因座在很宽的系统发育范围内的苍蝇物种。我们描述了第五个外显子，并表明该位点有一个复杂的进化历史与几个重复，pseudogenisations和损失的外显子。PAML分析表明，整个基因有一个历史的纯化选择，虽然这是不太强的外显子进行复制。外显子之间的功能分歧的估计是相似的复制基因之间的功能分歧的幅度，这表明外显子分歧是大致等同于基因复制。
Gene families typically evolve by gene duplication followed by the adoption of new or altered gene functions. A different way to evolve new but related functions is alternative splicing of existing exons of a complex gene. The chemosensory gene families of animals are characterised by numerous loci of related function. Alternative splicing has only rarely been reported in chemosensory loci, for example in 5 out of around 120 loci in Drosophila melanogaster. The gustatory receptor gene Gr39a has four large exons that are alternatively spliced with three small conserved exons. Recently the genome sequences of eleven additional species of Drosophila have become available allowing us to examine variation in the structure of the Gr39a locus across a wide phylogenetic range of fly species. We describe a fifth exon and show that the locus has a complex evolutionary history with several duplications, pseudogenisations and losses of exons. PAML analyses suggested that the whole gene has a history of purifying selection, although this was less strong in exons which underwent duplication. Estimates of functional divergence between exons were similar in magnitude to functional divergence between duplicated genes, suggesting that exon divergence is broadly equivalent to gene duplication.
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