Howard Hughes Medical Institute and Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA.
Proc Natl Acad Sci U S A. 2012 Dec 18;109(51):20975-9. doi: 10.1073/pnas.1207715109. Epub 2012 Nov 29.
Similar morphological, physiological, and behavioral features have evolved independently in different species, a pattern known as convergence. It is known that morphological convergence can occur through changes in orthologous genes. In some cases of convergence, cis-regulatory changes generate parallel modifications in the expression patterns of orthologous genes. Our understanding of how changes in cis-regulatory regions contribute to convergence is hampered, usually, by a limited understanding of the global cis-regulatory structure of the evolving genes. Here we examine the genetic causes of a case of precise phenotypic convergence between Drosophila sechellia and Drosophila ezoana, species that diverged ~40 Mya. Previous studies revealed that changes in multiple transcriptional enhancers of shavenbaby (svb, a transcript of the ovo locus) caused phenotypic evolution in the D. sechellia lineage. It has also been shown that the convergent phenotype of D. ezoana was likely caused by cis-regulatory evolution of svb. Here we show that the large-scale cis-regulatory architecture of svb is conserved between these Drosophila species. Furthermore, we show that the D. ezoana orthologs of the evolved D. sechellia enhancers have also evolved expression patterns that correlate precisely with the changes in the phenotype. Our results suggest that phenotypic convergence resulted from multiple noncoding changes that occurred in parallel in the D. sechellia and D. ezoana lineages.
不同物种中独立进化出相似的形态、生理和行为特征，这种模式被称为趋同进化。已知形态趋同进化可以通过同源基因的变化来实现。在某些趋同进化的情况下，顺式调控区的变化会导致同源基因表达模式的平行修饰。我们对顺式调控区变化如何促进趋同进化的理解通常受到进化基因全局顺式调控结构理解有限的阻碍。在这里，我们研究了果蝇 sechellia 和 Drosophila ezoana 之间精确表型趋同进化的遗传原因，这两个物种在大约 4000 万年前就已经分化。之前的研究表明，shavenbaby（ovo 基因座的转录本）的多个转录增强子的变化导致了果蝇 sechellia 谱系的表型进化。也表明，Drosophila ezoana 的趋同表型很可能是由 svb 的顺式调控进化引起的。在这里，我们展示了 svb 的大规模顺式调控结构在这些果蝇物种之间是保守的。此外，我们还表明，进化后的果蝇 sechellia 增强子的 D. ezoana 同源物的表达模式也发生了变化，与表型的变化精确相关。我们的研究结果表明，表型趋同是由果蝇 sechellia 和 D. ezoana 谱系中平行发生的多个非编码变化引起的。
