Ca²⁺-induced sporulation in Achlya bisexualis: reserve 1,3-β-glucans provide both carbon and phosphorus

Abstract

Reserve water-soluble 1,3-β-glucans represent some 13% (wt/wt) of the mycelial dry weight of Achlya, and consist of a small neutral form and a very large phosphorylated one. The phosphoglucan appears to be formed via aggregation of neutral molecules by phosphodiester linkages. Asexual sporulation in Achlya bisexualis, induced by 0.5 mM Ca²⁺, was accompanied by a 43% reduction in total glucan after 4 h, and the ratio of neutral glucan to phosphoglucan changed between 4 and 12 h. Phosphate content of the phosphoglucan declined by 50%, but the molecular size remained large and the ratio of mono- and diester linkages changed only slightly. Appropriate enzyme activities of β-glucanase and phosphoesterases capable of releasing both glucose and phosphate were found, and are described.

Key Words:

• asexual reproduction
• water molds
• neutral and phosphorylated reserve polysaccharides