Induction of a Biopolyester Hydrolase (Cutinase) by Low Levels of Cutin Monomers in Fusarium solani f. sp. pisi

Abstract

Cutin hydrolysate induced the production of an extracellular cutinase by glucose-grown Fusarium solani f. sp. pisi . The rate of production depended on the amount of cutin hydrolysate added up to 80 μg/ml, and saturation was attained at this level. Glucose was found to be a repressor of cutinase production. A radial immunodiffusion assay for cutinase was developed, and the induction of cutinase by cutin hydrolysate was confirmed by this direct assay. When cutinase was induced by cutin hydrolysate, exogenous labeled phenylalanine was incorporated into cutinase, which was shown to be the major (>70%) protein in the extracellular fluid. Induction of cutinase by cutin hydrolysate was not inhibited by actinomycin D and was stimulated (≃100%) by cordycepin. Addition of cycloheximide with the inducer, or up to 12 h after the addition of the inducer, resulted in a nearly immediate cessation of cutinase production. Deoxyglucose, an inhibitor of proten glycosylation, inhibited the induction of cutinase by cutin hydrolysate. ω-Hydroxy fatty acids were more effective in inducing cutinase than any of the other more polar acids of cutin. Experiments with derivatives and analogues of ω-hydroxy C 16 acid indicated that a free hydroxyl group at the ω-position was the most important factor determining the cutinase-inducing activity. n -Aliphatic primary alcohols with 14 or more carbon atoms induced cutinase, and n -C 16 was the most effective inducer. These results strongly suggest that the monomers function as the chemical signal which induces the extracellular hydrolase.