CUTINASE AND OTHER LIPOLYTIC ESTERASES PROTECT BEAN-LEAVES FROM INFECTION BY RHIZOCTONIA-SOLANI

The results describe a novel activity of fungal cutinase, the protecti on of bean leaves from disease. Development of web blight symptoms on bean leaves infected with Rhizoctonia solani (AG-l) was prevented in t he presence of cutinase purified from Venturia inaequalis. Instead of disease, small areas of tissue necrosis became visible, and the tissue in which the pathogen was restricted displayed strong autofluorescenc e beneath the inoculation sites. Mechanical wounding of the leaf surfa ce had no effect on disease development and the permeability of the cu ticle was not increased by cutinase action, indicating that surface wo unding was not the cause for this novel activity of cutinase. A compar ative study involving cutinase and of her serine hydrolases revealed t hat the disease prevention resided in the lipolytic esterase activity rather than the cutinase activity. The pattern of expression of four p athogenesis-related (PR) protein genes provided no evidence for the mo dulation of known resistance responses of bean leaves in response to c utinase action. The protective mechanism of the esterase activity rema ins unknown.