Wang Xiaodong, Greenberg Jennifer F, Chamberlin Helen M
Department of Molecular Genetics, Ohio State University, Columbus, OH 43210, USA.
Evol Dev. 2004 Jul-Aug;6(4):237-45. doi: 10.1111/j.1525-142X.2004.04029.x.
Natural selection acts at the level of function, not at the logistical level of how organisms achieve a particular function. Consequently, significant DNA sequence and regulatory differences can achieve the same function, such as a particular gene expression pattern. To investigate how regulatory features underlying a conserved function can evolve, we compared the regulation of a conserved gene expression pattern in the related species Caenorhabditis elegans and C. briggsae. We find that both C. elegans and C. briggsae express the ovo-related zinc finger gene lin-48 in the same pattern in hindgut cells. However, the regulation of this gene by the Pax-2/5/8 protein EGL-38 differs in two important ways. First, specific differences in the regulatory sequences of lin-48 result in the presence of two redundant EGL-38 response elements in C. elegans, whereas the redundancy is absent in C. briggsae. Second, there is a single egl-38 gene in C. briggsae. In contrast, the gene is duplicated in C. elegans, with only one copy retaining the ability to regulate lin-48 in vivo. These results illustrate molecular changes that can occur despite maintenance of conserved gene function in different species.
自然选择作用于功能层面，而非生物体实现特定功能的逻辑层面。因此，显著的DNA序列和调控差异能够实现相同的功能，比如特定的基因表达模式。为了研究保守功能背后的调控特征是如何进化的，我们比较了相关物种秀丽隐杆线虫和briggsae线虫中保守基因表达模式的调控情况。我们发现，秀丽隐杆线虫和briggsae线虫在后肠细胞中以相同模式表达与ovo相关的锌指基因lin-48。然而，Pax-2/5/8蛋白EGL-38对该基因的调控在两个重要方面存在差异。首先，lin-48调控序列的特定差异导致秀丽隐杆线虫中存在两个冗余的EGL-38反应元件，而briggsae线虫中不存在这种冗余。其次，briggsae线虫中有一个单一的egl-38基因。相比之下，秀丽隐杆线虫中的该基因发生了复制，只有一个拷贝保留了在体内调控lin-48的能力。这些结果说明了尽管不同物种中保守基因功能得以维持，但仍可能发生的分子变化。
