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

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Abstract
Cutin hydrolysate induced the production of an extracellular cutinase by glucose-grown F. solani f. sp. pisi. The rate of production depended on the amount of cutin hydrolysate added up to 80 .mu.g/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 (.simeq. 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 protein glycosylation, inhibited the induction of cutinase by cutin hydrolysate. .omega.-Hydroxy fatty acids were more effective in inducing cutinase than any of the other more polar acids of cutin. Experiments with derivatives and analogs of .omega.-hydroxy C16 acid indicated that a free hydroxyl group at the .omega.-position was the most important factor determining the cutinase-inducing activity. n-Aliphatic primary alcohols with 14 or more C atoms induced cutinase, and n-C16 was the most effective inducer. These results strongly suggest that the monomers function as the chemical signal which induces the extracellular hydrolase.