A glycosylphosphatidylinositol-anchored α-amylase encoded by amyD contributes to a decrease in the molecular mass of cell wall α-1,3-glucan in Aspergillus nidulans

Abstract

-1,3-Glucan is one of the main polysaccharides in the cell wall of Aspergillus nidulans. We previously revealed that it plays a role in hyphal aggregation in liquid culture, and that its molecular mass (MM) in an agsA-overexpressing (agsAOE) strain was larger than that in an agsB-overexpressing (agsBOE) strain. The mechanism that regulates the MM of -1,3-glucan is poorly understood. Although the gene amyD, which encodes glycosyl-phosphatidylinositol (GPI)-anchored -amylase (AmyD), is involved in the biosynthesis of -1,3-glucan in A. nidulans, how it regulates this biosynthesis remains unclear. Here we constructed strains with disrupted amyD ({Delta}amyD) or overexpressed amyD (amyDOE) in the genetic background of the ABPU1 (wild-type), agsAOE, or agsBOE strain, and characterized the chemical structure of -1,3-glucans in the cell wall of each strain, focusing on their MM. The MM of -1,3-glucan from the agsBOE amyDOE strain was smaller than that in the parental agsBOE strain. In addition, the MM of -1,3-glucan from the agsAOE {Delta}amyD strain was greater than that in the agsAOE strain. These results suggest that AmyD is involved in decreasing the MM of -1,3-glucan. We also found that the C-terminal GPI-anchoring region is important for these functions.