The mating type protein Mat1-2 from asexual Aspergillus fumigatus drives sexual reproduction in fertile Aspergillus nidulans

Department of Microbiology Molecular Biology and Biochemistry, Center for Reproductive Biology, University of Idaho, Moscow, ID, U.S.A

^* To whom correspondence should be addressed. Email: bmiller{at}uidaho.edu.

	Abstract

The lack of an experimentally amenable sexual genetic system in Aspergillus fumigatus (Af) is a major limitation in the study of its pathogenesis. Recent comparative genome analysis revealed evidence for potential sexuality in Af. Homologs of mating type genes as well as other genes of the "sexual machinery" have been identified in anamorphic Af. The mat1-2 gene encodes a homolog of the MatA HMG-box mating transcriptional factor that regulates sexual development in fertile Aspergillus nidulans (An). In this study the functionality of Af mat1-2 and the Mat1-2 protein was determined by interspecies gene exchange between sterile Af and fertile An. Ectopically integrated Af mat1-2 (driven by its own promoter) was not functional in a sterile An matA strain and no sexual development was observed. In contrast, the Af mat1-2 ORF driven by the An matA promoter and integrated by homologous gene replacement at the matA locus was functional and conferred full fertility. This is the first report showing that cross species mating type gene exchange between closely related Ascomycetes did not function in sexual development. This is also the first report demonstrating that a Mat^HMG protein from an asexual species is fully functional, with viable ascospore differentiation, in a fertile homothallic species. Expression of mat1-2 was assessed in Af and An. Our data suggest that mat1-2 may not be properly regulated to allow sexuality in Af. This study provides new insights about Af asexuality and also suggests the possibility for development of an experimentally amenable sexual cycle.