The fungal pathogen Aspergillus fumigatus regulates growth, metabolism, and stress resistance in response to light.

Light is a pervasive environmental factor that regulates development, stress resistance, and even virulence in numerous fungal species. Though much research has focused on signaling pathways in Aspergillus fumigatus, an understanding of how this pathogen responds to light is lacking. In this report, we demonstrate that the fungus does indeed respond to both blue and red portions of the visible spectrum. Included in the A. fumigatus light response is a reduction in conidial germination rates, increased hyphal pigmentation, enhanced resistance to acute ultraviolet and oxidative stresses, and an increased susceptibility to cell wall perturbation. By performing gene deletion analyses, we have found that the predicted blue light receptor LreA and red light receptor FphA play unique and overlapping roles in regulating the described photoresponsive behaviors of A. fumigatus. However, our data also indicate that the photobiology of this fungus is complex and likely involves input from additional photosensory pathways beyond those analyzed here. Finally, whole-genome microarray analysis has revealed that A. fumigatus broadly regulates a variety of metabolic genes in response to light, including those involved in respiration, amino acid metabolism, and metal homeostasis. Together, these data demonstrate the importance of the photic environment on the physiology of A. fumigatus and provide a basis for future studies into this unexplored area of its biology. IMPORTANCE Considerable effort has been taken to understand how the mold pathogen Aspergillus fumigatus senses its environment to facilitate growth within the immunocompromised host. Interestingly, it was shown that the deletion of a blue light photoreceptor in two divergent fungal pathogens, Cryptococcus neoformans and Fusarium oxysporum, leads to an attenuation of virulence in their respective animal infection models. This suggests that light signaling pathways are conservatively involved in the regulation of fungal pathogenesis. However, an understanding of whether and how A. fumigatus responds to light is lacking. Here we demonstrate that this organism coordinates broad aspects of its physiology with the photic environment, including pathways known to be involved in virulence, such as carbohydrate metabolism and oxidative stress resistance. Moreover, the photoresponse of A. fumigatus differs in notable ways from the well-studied model Aspergillus nidulans. Therefore, this work should represent a general advancement in both photobiology and A. fumigatus research communities.