W. Maccheroni et Jl. Azevedo, Synthesis and secretion of phosphatases by endophytic isolates of Colletotrichum musae grown under conditions of nutritional starvation, J GEN A MIC, 44(6), 1998, pp. 381-387
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.