Functional analysis of the a-1,3-glucan synthase genes agsA and agsB in Aspergillus nidulans: agsB is the major a-1,3-glucan synthase in this fungus. PLoS One 8: e54893

Although a-1,3-glucan is one of the major cell wall polysaccharides in filamentous fungi, the physiological roles of a-1,3-glucan remain unclear. The model fungus Aspergillus nidulans possesses two a-1,3-glucan synthase (AGS) genes, agsA and agsB. For functional analysis of these genes, we constructed several mutant strains in A. nidulans: agsA disruption, agsB disruption, and double-disruption strains. We also constructed several CagsB strains in which agsB expression was controlled by the inducible alcA promoter, with or without the agsA-disrupting mutation. The agsA disruption strains did not show markedly different phenotypes from those of the wild-type strain. The agsB disruption strains formed dispersed hyphal cells under liquid culture conditions, regardless of the agsA genetic background. Dispersed hyphal cells were also observed in liquid culture of the CagsB strains when agsB expression was repressed, whereas these strains grew normally in plate culture even under the agsB-repressed conditions. Fractionation of the cell wall based on the alkali solubility of its components, quantification of sugars, and 13C-NMR spectroscopic analysis revealed that a-1,3-glucan was the main component of the alkali-soluble fraction in the wild-type and agsA disruption strains, but almost no a-1,3-glucan was foun