Phytochrome-dependent light signaling has been studied in several fungi. In Aspergillus nidulans light-stimulated phytochrome activates the high-osmolarity glycerol (HOG) signaling pathway and thereby controls the expression of a large number of genes, many of which are related to stress responses. In a genome-wide expression analysis in A. nidulans we found that phytochrome, fphA, is under strict expression control of the central regulator of the sulfur-starvation response, MetR. This transcriptional regulator is required for the expression of genes involved in inorganic sulfur assimilation. In the presence of organic sulfur, MetR is probably ubiquitinated and possibly degraded and the transcription of sulfur-assimilation genes, e.g., sulfate permease, is turned off. The expression analysis described here revealed, however, that MetR additionally controls the expression of hundreds of genes, many of which are required for secondary metabolite production. We also show that metR mutation phenocopies fphA deletion, and five other histidine-hybrid kinases are down-regulated in the metR1 mutant. Furthermore, we found that light and phytochrome regulate the expression of at least three carbon–sulfur hydrolases. This work is a further step towards understanding the interplay between light sensing and metabolic pathways.

已经在几种真菌中研究了光敏色素依赖性光信号。在构巢曲霉中，光刺激的光敏色素激活高渗透压甘油 (HOG) 信号通路，从而控制大量基因的表达，其中许多基因与应激反应有关。在A. nidulans的全基因组表达分析中，我们发现光敏色素fphA, 受到硫饥饿反应的中央调节器 MetR 的严格表达控制。这种转录调节因子是参与无机硫同化的基因表达所必需的。在有机硫存在的情况下，MetR 可能被泛素化并可能被降解，并且硫同化基因（例如硫酸盐通透酶）的转录被关闭。然而，此处描述的表达分析显示，MetR 还控制着数百个基因的表达，其中许多基因是次级代谢产物生产所必需的。我们还表明metR突变表型复制fphA缺失，并且其他五种组氨酸杂交激酶在metR1中下调变种人。此外，我们发现光和光敏色素调节至少三种碳硫水解酶的表达。这项工作进一步了解了光感和代谢途径之间的相互作用。