Chair of Evolutionary Ecology, Ludwig-Maximilians Universität München, Faculty of Biology, Biozentrum, Grosshaderner Strasse 2, 82152 Planegg-Martinsried, Germany.
Sci Adv. 2023 Feb 17;9(7):eade6529. doi: 10.1126/sciadv.ade6529.
The loss of discrete morphological traits, the most common evolutionary transition, is typically driven by changes in developmental gene expression. Mutations accumulating in regulatory elements of these genes can disrupt DNA binding sites for transcription factors patterning their spatial expression, or delete entire enhancers. Regulatory elements, however, may be silenced through changes in chromatin accessibility or the emergence of repressive elements. Here, we show that increased chromatin accessibility at the gene , combined with the gain of a repressor site, underlies the loss of a wing spot pigmentation pattern in a species. The gain of accessibility of this repressive element is regulated by E93, a transcription factor governing the progress of metamorphosis. This convoluted evolutionary scenario contrasts with the parsimonious mutational paths generally envisioned and often documented for morphological losses. It illustrates how evolutionary changes in chromatin accessibility may directly contribute to morphological diversification.
离散形态特征的丧失是最常见的进化转变，通常是由发育基因表达的变化驱动的。这些基因的调控元件中积累的突变可以破坏转录因子的 DNA 结合位点，从而改变其空间表达模式，或者删除整个增强子。然而，调控元件可能会通过染色质可及性的变化或抑制性元件的出现而沉默。在这里，我们表明，在一个物种中，基因的染色质可及性增加，加上一个抑制性位点的获得，是翅膀斑点色素沉着模式丧失的基础。这个抑制性元件的可及性的获得是由 E93 调控的，E93 是一个控制变态进程的转录因子。这种复杂的进化情景与通常为形态学缺失所设想和经常记录的简约突变路径形成对比。它说明了染色质可及性的进化变化如何直接有助于形态多样化。
