ACID-PHOSPHATASE SECRETION BY BOTRYTIS-CINEREA

Botrylis cinerea secreted low levels of a constitutive acid phosphatas e into liquid culture when grown in the condition of phosphate starvat ion or in the presence of high concentrations (4 mM) of organic phosph ate esters or inorganic phosphate. During phosphate starvation the ove rall acid phosphatase activity secreted into the culture fluid was inc reased up to 80-fold due to the appearance of a second (phosphate-repr essible) enzyme form. On native polyacrylamide electrophoresis gels, t he constitutive enzyme displayed size heterogeneity, whereas the repre ssible enzyme was resolved as a discrete band. Both forms of the enzym e reacted with p-nitrophenylphosphate under such conditions, but only the constitutive form was found to hydrolyse beta-glycerophosphate. Hi stochemical staining with these two substrates with the Gomori lead-ca pture method revealed significant staining of secretory vesicles in th e hyphal tip region only in phosphate-starved mycelium with p-nitrophe nylphosphate as the substrate. By contrast, vacuolar structures were s tained with both substrates under conditions of phosphate starvation a s well as abundance of inorganic phosphate. The implications of these observations for the likely exit route of the two acid phosphatase for ms are discussed.