Ustilago maydis encodes ten predicted light-sensing proteins. The biological functions of only a few of them are elucidated. Among the characterized ones are two DNA-photolyases and two rhodopsins that act as DNA-repair enzymes or green light-driven proton pumps, respectively. Here we report on the role of two other photoreceptors in U. maydis, namely White collar 1 (Wco1) and Phytochrome 1 (Phy1). We show that they bind flavins or biliverdin as chromophores, respectively. Both photoreceptors undergo a photocycle in vitro. Wco1 is the dominant blue light receptor in the saprophytic phase, controlling all of the 324 differentially expressed genes in blue light. U. maydis also responds to red and far-red light. However, the number of red or far-red light-controlled genes is less compared to blue light-regulated ones. Moreover, most of the red and far-red light-controlled genes not only depend on Phy1 but also on Wco1, indicating partial coregulation of gene expression by both photoreceptors. GFP-fused Wco1 is preferentially located in the nucleus, Phy1 in the cytosol, thus providing no hint that these photoreceptors directly interact or operate within the same complex. This is the first report on a functional characterization and coaction of White collar 1 and phytochrome orthologs in basidiomycetes.

Ustilago maydis编码十种预测的光敏蛋白。仅阐明了其中少数的生物学功能。其中有特征的是两种 DNA 光解酶和两种视紫质，它们分别充当 DNA 修复酶或绿光驱动的质子泵。在这里，我们报告了U. maydis 中其他两种光感受器的作用，即白领 1 (Wco1) 和光敏色素 1 (Phy1)。我们表明它们分别将黄素或胆绿素结合为发色团。两种光感受器都在体外经历光循环。Wco1 是腐生期的主要蓝光受体，控制着蓝光下的所有 324 个差异表达基因。梅迪斯对红光和远红光也有反应。然而，与蓝光调节基因相比，红光或远红光控制基因的数量较少。此外，大多数红光和远红光控制基因不仅依赖于 Phy1，还依赖于 Wco1，表明两种光感受器对基因表达的部分共调。GFP 融合的 Wco1 优先位于细胞核中，Phy1 位于细胞质中，因此没有暗示这些光感受器直接相互作用或在同一复合物中运行。这是关于担子菌中白领 1 和光敏色素直向同源物的功能表征和相互作用的第一份报告。