Abstract
The secretion of hydrolases by Beauveria bassiana is a main factor in the degradation of cuticle, while in filamentous fungi the resistance to 2-deoxy-d-glucose (2DG) is related to enzymatic deregulation. A series of 2DG-resistant B. bassiana strains were classified according to the phenotypes of germination (G) and radial growth rate (Ur), in addition to their virulence parameters on Tenebrio molitor. This analysis allowed distinction between mutants with greater (881.2) and lesser (884.5) G and Ur values, relative to the wild-type strain (88), which correlated with virulence parameters including maximal mortality (M) and time to reach 50% mortality (LT50). Subsequently, using the cuticle of T. molitor as the substrate for these strains, an enzymatic analysis (total proteases, Pr1, chitinases and β-N-acetylglucosaminidase) showed that the contrasting virulence traits were associated with different deregulation patterns: higher specific activities (up to 100%) for the more virulent mutant 881.2 and lower enzymatic levels for mutant 884.5, specifically chitinases (33% reduction), relative to the wild-type strain (88) for both mutants. The differences in cuticle-degrading enzymes were consistent with the appearance of hyphal bodies within infected insects. This is the first study describing the altered enzymatic profiles in 2DG-resistant mutants of B. bassiana with practical implications in the selection of improved strains for biological control.
Published Version
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