Department of Biology, Duke University, Durham, NC 27704, USA.
Curr Biol. 2011 Apr 26;21(8):700-4. doi: 10.1016/j.cub.2011.03.028. Epub 2011 Apr 7.
Identifying the genetic basis of parallelism reveals the means by which evolution repeats itself and shows what aspects-if any-may be predictable. The recently tetraploid luteus group of Mimulus contains five species native to central Chile, three of which have evolved extensive red floral pigmentation using at least two distinct loci . Here we show that the parallel evolution of petal lobe anthocyanin (PLA) pigmentation in M. cupreus and M. luteus var. variegatus occurred via separate yet strikingly similar mechanisms. In each case, a dominant, single-locus gain of pigmentation maps to a genomic region (pla1 and pla2, respectively) containing adjacent, apparently recently duplicated paralogs of MYB anthocyanin-regulating transcription factors. Interestingly, candidate genes in pla1 and pla2 are themselves related by an older duplication. In both cases, pla genotype cosegregates with expression of multiple genes in the anthocyanin biosynthetic pathway, revealing a mechanism of coordinated trans-regulatory expression changes across functionally related enzyme-encoding genes. We conclude that in this instance, evolution has repeated itself with marked consistency. Duplication has enabled that repetition to occur using two physically independent but functionally similar loci, highlighting the importance of genomic complexity to the evolutionary process.
确定平行进化的遗传基础揭示了进化重复自身的方式，并表明哪些方面（如果有的话）可能是可预测的。最近的四倍体 Mimulus luteus 组包含五种原产于智利中部的物种，其中三种利用至少两个不同的基因座进化出了广泛的红色花色素沉着。在这里，我们表明，M. cupreus 和 M. luteus var. variegatus 花瓣裂片花青素（PLA）色素沉着的平行进化是通过独立但惊人相似的机制发生的。在每种情况下，显性、单基因座的色素沉着增益都映射到一个基因组区域（分别为 pla1 和 pla2），其中包含相邻的、显然是最近复制的 MYB 花青素调节转录因子的旁系同源物。有趣的是，pla1 和 pla2 中的候选基因本身通过较旧的复制而相关。在这两种情况下，pla 基因型与花青素生物合成途径中的多个基因的表达共分离，揭示了跨功能相关酶编码基因的协调反式调节表达变化的机制。我们得出的结论是，在这种情况下，进化具有显著的一致性。复制使进化能够使用两个物理上独立但功能上相似的基因座重复发生，突出了基因组复杂性对进化过程的重要性。
