Overexpression of Aspergillus nidulans α-1,3-glucan synthase increases cellular adhesion and causes cell wall defects

Abstract

Alpha-1,3-glucan is important for pathogenesis by Aspergillus fumigatus, but the mechanism is unclear since the deletion has no hyphal phenotype. We dissected the roles of A. nidulans α-1,3-glucan in constitutive overexpression strains. Constitutive high-level α-1,3-glucan synthase activity increased hyphal wall thickness, but colonies grew slowly and sporulated poorly and had much higher adhesion to hydrophobic materials. Surprisingly, this overexpression strain formed a biofilm-like structure in plastic culture wells that was as adhesive as wild-type A. fumigatus. These results suggest α-1,3-glucan has important roles in fungal cellular adhesion and may contribute to fungal pathogenesis.

Cell wall glucans of fungi. A review

“…If the amounts of the polysaccharide were low, no cleistothecia were formed ( Zonneveld, 1972 ). Another example of wall alterations by the levels of α 1,3 glucan was the observation that overexpresion of the synthesizing enzyme increased cellular adhesion and wall defects of A. nidulans ( He et al, 2018 ).…”

Characterization of Aspergillus nidulans Biofilm Formation and Structure and Their Inhibition by Pea Defensin Psd2

“…A. nidulans is phylogenetically related to other species of economic importance, including A. niger and A. oryzae and clinically relevant species such as A. fumigatus (Galagan et al, 2005). Previous studies have described the A. nidulans adhesion in hydrophobic surfaces and their biofilm development, both of which are critical for the virulence of Aspergillus species (Shukla et al, 2017;He et al, 2018;Kadry et al, 2018;Lingo et al, 2021). Kadry et al (2018) used scanning electron microscopy (SEM) and found that A. nidulans strains (ΔgmtA and ΔgmtB) did not produce guanosine diphosphate mannose transporter (GMT), a transporter required for mannosylation of galactomannan and mannoproteins, exhibited smaller colony size, reduced sporulations, increased hyphal width and decreased based cell length.…”

“…In addition, the spores of A. nidulans ΔgmtA had a rougher surface than the wild-type strain, being less adhesive to polystyrene plates, reducing the biofilm formation (Kadry et al, 2018). He et al (2018) evaluated the role of α-1,3-glucan, a primary cell wall component in many filamentous fungi, including in A. nidulans biofilm formation. The overexpression of α-1,3-glucan synthase in A. nidulans triggered a higher cellular adhesion to hydrophobic materials and biofilm formation than the wild-type strain, which could contribute to fungal virulence (He et al, 2018).…”

“…He et al (2018) evaluated the role of α-1,3-glucan, a primary cell wall component in many filamentous fungi, including in A. nidulans biofilm formation. The overexpression of α-1,3-glucan synthase in A. nidulans triggered a higher cellular adhesion to hydrophobic materials and biofilm formation than the wild-type strain, which could contribute to fungal virulence (He et al, 2018). Those findings may indicate that cell adhesion to hydrophobic surfaces can contribute, and it is required to the biofilm formation of A. nidulans (He et al, 2018;Kadry et al, 2018).…”

Aspergillus nidulans AmyG Functions as an Intracellular α-Amylase to Promote α-Glucan Synthesis

“…Apart from that, we and other groups found that α-glucan is critical for conidial adhesion ( 3 , 4 , 10 ). Artificial overexpression of α-glucan in Aspergillus nidulans could trigger cell wall reconstitution and thus promote fungal cell adhesion and biofilm formation ( 11 ).…”