LAUSR

BACKGROUND The fungal cell wall integrity is vital for fungal pathogenesis and stress tolerance. Calcofluor white (CFW), a cell wall perturbing agent, inhibits fungal growth by binding chitin in the cell wall. The roles of CFW sensitive proteins remain understood insufficiently in pathogenic fungi. RESULTS We investigated two calcofluor white hypersensitive proteins MaCwh1 and MaCwh43 in entomopathogenic fungus, Metarhizium acridum. Both GFP-tagged MaCwh1 and MaCwh43 localized at endoplasmic reticulum. Our results showed that the ΔMacwh1 and ΔMacwh43 mutants were more sensitive to CFW and ultraviolet irradiation stress compared to wild type and complement strains. ΔMacwh1 had a stronger sensitivity to these stresses than ΔMacwh43. Both ΔMacwh1 and ΔMacwh43 mutants showed smoother cell wall surface, drastically reduced chitin and mannose glycoprotein level in cell wall and glycerol level in conidia compared to wild type. Insect bioassay showed significantly attenuated virulence for both ΔMacwh1 and ΔMacwh43 mutants with impaired ability in penetrating the host cuticle. RNA-Seq analysis revealed that a large number of genes presumably involved in cell wall construction and modification, pathogenicity and stress response were downregulated in both ΔMacwh1 and ΔMacwh43 mutants. CONCLUSIONS These findings demonstrated that both Macwh1 and Macwh43 affected the fungal cell wall ultrastructure and contributed to the stress tolerance and pest control potential in M. acrdium.