Disruption of β-N-acetylhexosaminidase Hex2 attenuates virulence in Beauveria bassiana through cell wall disturbance and developmental defects.

Abstract

Entomopathogenic fungi such as Beauveria bassiana represent promising alternatives to chemical pesticides, yet their morphogenesis and environmental adaptation depend critically on dynamic cell wall remodeling. Despite the essential role of β-N-acetylhexosaminidase (Hex) in cell wall decomposition, its potential contributions to fungal biocontrol remain unexplored. Here, we identified and functionally dissected a previously uncharacterized homology, Hex2. Notably, Hex2 deficiency led to irregular cell wall structure by elevating chitin, N-glycan contents and protein N-/O-glycosylation levels within it. In addition, ΔHex2 mutant exhibited impaired development, including defects in sporulation, germination, and dimorphic transitions. These developmental defects were likely attributed to aberrant accumulation of cell wall components rather than insufficient ATP production. More interestingly, losing Hex2 enhanced fungal tolerance to oxidative stress cues though upregulation of antioxidant enzyme activities. Despite heightened oxidative-stress resistance, ΔHex2 mutant displayed significantly attenuated virulence against Galleria mellonella larvae, indicating that cell-wall disturbance and developmental defects might constitute the predominant causes of reduced pathogenicity. These findings provide the first insights into the multifaceted roles of intracellular β-N-acetylhexosaminidase Hex2 in B. bassiana, identifying a rational target for engineering insecticides with remained or even enhanced pesticidal efficacy.