A Dictyostelium discoideum cellulase is a member of a spore germination-specific gene family

Abstract

A member of the 270 spore germination-specific gene family in Dictyostelium discoideum is shown to encode a cellulase (endo-(1,4)-beta-D-glucanase, EC 3.2.1.4) activity. The 270-6 deduced protein shows 38% identity and 58% similarity to an avocado (Persea americana) cellulase. During spore germination in Dictyostelium extracellular cellulase activity starts to accumulate coincident with the appearance of the 270-6 gene transcript. Amoebae transformed by a vector containing the 270-6 mRNA sequence express an extracellular cellulase during vegetative growth when there would otherwise be no cellulase activity. In addition, the expression of a truncated 270-6 polypeptide lacking the 270 gene family-defining tetrapeptide repeat and the C-terminal region, in suitably transformed amoebae, also produces an extracellular cellulase activity. Several differently sized cellulase activities are shown to accumulate during spore germination, and it is possible that the 270 gene family represents a coordinately expressed family of cellulases.