Properties of a cutinase-defective mutant of Fusarium solani.
1989
Dantzig A.H.
The fungal plant pathogen Fusarium solani produces an extracellular enzyme, cutinase, which catalyzes the degradation of the bipolymer, cutin, in the plant cuticle. The enzyme was repressed when the microorganism was grown on a medium containing glucose and induced to high levels by cutin or its hydrolysis products, the true inducers. In the present study, culture filtrates contained basal levels of cutinase when Fusarium was grown on 0.5% acetate as the sole carbon source and high levels of cutinase when grown on cutin. After mutagenesis, a cutinase-defective mutant of Fusarium was identified by screening acetate-grown colonies for a loss of enzyme activity. The mutant exhibited an 80-90% reduction in cutinase activity under several growth conditions due to a quantitative reduction in a qualitatively normal enzyme. The mutant also exhibited a reduction in virulence in the pea stem bioassay. Taken together, these data indicated that a growth condition exists where the cutinase enzyme was neither induced nor repressed and was present in basal levels. This condition may pose the pathogen for rapid enzyme induction when in the proximity of the plant cuticle. The cutinase-defective mutant was either a regulatory mutant with an altered expression of cutinase, or a mutant modified in its ability to excrete the enzyme.
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