The GAL pathway of yeasts has long served as a model system for understanding of how regulatory mode of eukaryotic metabolic pathways evolves. While Gal4 mode has been well-characterized in Saccharomycetaceae clade, little is known about the regulation of the GAL pathway in other yeasts. Here, we find that Rep1, a Ndt80-like family transcription factor, serves as a galactose sensor in the commensal-pathogenic fungus Candida albicans. It is presented at the GAL gene promoters independent of the presence of galactose. Rep1 recognizes galactose via a direct physical interaction. The net result of this interaction is the recruitment of a transcriptional activator Cga1 (Candida galactose gene activator, orf19.4959) and transcription of the GAL genes proceeds. Rep1 and Cga1 are conserved across the CTG species. Rep1 itself does not possess transcriptional activity. Instead, it provides a scaffold to recruit different factors for transcriptional regulation. Rep1-Cga1 mode of regulation represents a new example of network rewiring in fungi, which provides insight into how C. albicans evolves transcriptional programs to colonize diverse host niches.

中文翻译：

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支架蛋白对半乳糖的识别为白色念珠菌中的 GAL 调节子诱导招募转录激活剂

酵母的GAL途径长期以来一直作为模型系统来理解真核代谢途径的调节模式如何演变。虽然 Gal4 模式已在酵母菌科进化枝中得到充分表征，但对其他酵母中GAL通路的调节知之甚少。在这里，我们发现 Rep1 是一种 Ndt80 样家族转录因子，在共生致病真菌白色念珠菌中充当半乳糖传感器。它在GAL上展示独立于半乳糖存在的基因启动子。Rep1 通过直接的物理相互作用识别半乳糖。这种相互作用的最终结果是转录激活因子 Cga1（念珠菌半乳糖基因激活因子，orf19.4959）的募集和GAL基因的转录。Rep1 和 Cga1 在 CTG 物种中是保守的。Rep1 本身不具有转录活性。相反，它提供了一个支架来招募不同的转录调控因子。Rep1-Cga1 调控模式代表了真菌中网络重新布线的一个新例子，它提供了对白色念珠菌如何进化转录程序以殖民不同宿主生态位的深入了解。