Pathogenic fungi have gained increasing attention over the last decades as being a menace especially for the immunocompromised individual. The outcome of infection of a susceptible host depends on an array of multiple factors, and from latest studies different patterns that determine fungal pathogenicity have emerged. Most recently, the role of sex is under discussion, based on the fact that the most common fungal pathogens responsible for systemic diseases in humans appear to have retained sexuality although with limited access to meiotic reproduction. Among the aspergilli, A. fumigatus is by far the most frequent species to cause disease, and knowledge on the underlying cellular attributes for this is still scarce. Based on the working hypothesis that this pathogen, although appearing as asexual, has retained some cryptic sexuality, we aim at conserved key factors of sexual development. For that purpose, any conserved function of the A. fumigatus NsdD orthologue was examined in complementation and over-expression studies. When expressed in A. nidulans, the A. fumigatus gene is able to rescue the deletion phenotype of acleistothecial development. Moreover, forced expression of AfNsdD in A. nidulans results in predominant sexual development in this host. When either transcription factor, AfNsdD or AnNsdD, is expressed at high levels in the deuteromycete A. fumigatus, no formation of mature fruiting bodies is evident - however, unusual coiled hyphae are formed, and this is independent of the recipient’s mating-type. In conclusion, first evidence is provided that that the genome of the presumably asexual pathogen A. fumigatus encodes a functionally conserved positive regulator of sexual development. This transcriptional activator is able to trigger the formation of morphological structures that may resemble first stages of sexual development.
Full conference title:
9th EUROPEAN CONFERENCE ON FUNGAL GENETICS
- ECFG 9th (2008)