Synthesis and secretion of phosphatases by endophytic isolates of Colletotrichum musae grown under conditions of nutritional starvation

Even though fungal phosphatases are widely used to study ambient-regulated gene expression, little is known about these enzymes in the agriculturally important genus Colletotrichum. We have therefore identified several phosph atase activities in endophytic isolates of Colletotrichum musae grown under conditions of nutritional sufficiency or starvation for sources of phospho rus (P), nitrogen (N), carbon (C), and sulphur (S), These enzyme forms coul d be distinguished by substrate specificity, optimum pH, activation and inh ibition by some substances, response to nutritional starvation, and pattern of migration in native gel electrophoresis. At least four individual phosp hatase activities were identified under the growth conditions employed. A p H 5.0 acid phosphatase and an Mg2+-dependent pH 7.5 phosphodiesterase were expressed under ail growth conditions at constant rates. Under conditions o f P-starvation, derepression of a major pH 6.0-acid phosphatase was observe d in cell-free extracts and the culture medium. A synthesis of alkaline pho sphatase activities followed a more distinct pattern. Under conditions of n utritional sufficiency of P- or N-starvation, only a single intracellular e nzyme form (optimum pH 10) was observed, which was resolved as a single ele ctrophoretic activity band. However, in media lacking C or S sources additi onal alkaline phosphatase forms were derepressed with a concomitant increas e in the overall enzyme activity level measured at pH 10. To our knowledge, this report represents the most detailed study of phosphatases in Colletot richum and the first partial characterization of the phosphatase system in an endophytic fungus.