Deletion of the msdS/AfmsdC gene induces abnormal polarity and septation in Aspergillus fumigatus.

alpha-Mannosidases play an important role in the processing of mannose-containing glycans in eukaryotes. A deficiency in alpha-mannosidase is lethal in humans and cattle. In contrast to mammals, Saccharomyces cerevisiae does not require the endoplasmic reticulum alpha-mannosidase gene for growth. However, little is known of the consequence of loss of function of class I alpha-mannosidases in filamentous fungi. In this study, the msdS/AfmsdC gene was identified to encode 1,2-alpha-mannosidase MsdS in Aspergillus fumigatus. Soluble MsdS expressed in Escherichia coli was characterized as a typical class I alpha-mannosidase. The msdS gene was deleted by replacement of the msdS gene with a pyrG gene. Although the mutant showed a defect in N-glycan processing, as well as a reduction of cell wall components and a reduced ability of conidiation, it appeared that the rate of hyphal growth was not affected. Morphology analysis revealed abnormal polarity and septation at the stages of germination, hyphal growth and conidiation. Although the mechanism by which the N-glycan processing affects polarity and septation is unclear, our results show that msdS is involved in polarity and septation in A. fumigatus.