DIFFERENCES IN WALL STRUCTURE BETWEEN SUBSTRATE HYPHAE AND HYPHAE OF FRUIT-BODY STIPES IN AGARICUS-BISPORUS

In contrast to apical elongation in colonizing substrate hyphae, the hyphae in expanding mushrooms grow by diffuse extension over their whole wall surface. In Agaricus bisporus no significant differences were found in gross chemical wall composition of the two hyphal types. Similar amounts of glucosaminoglycan, with acetylated and non-acetylated glucosamine residues, and β-glucan were found. In both cases most of the (1 → 3)-β/(1 → 6)-β-glucan occurred in an alkali-insoluble form, probably effected by covalent linkage to glucosaminoglycan chains. However, glucosaminoglycan in elongating stipe walls was more susceptible to chitinase and a correlation was demonstrated between the competence of the hyphae to expand, enhanced susceptibility of the β-glucan to enzymic degradation, and a larger proportion of (1 → 6)-β-linked glucose side-branches in the β-glucan. Hydrogen-bonding among homologous chains in the glucosaminoglycan-glucan complex in walls of elongating stipe hyphae may therefore be relatively weak compared to that in non-elongating stipe hyphae and substrate hyphae. © 1990, British Mycological Society. All rights reserved.