LysM Proteins Regulate Fungal Development and Contribute to Hyphal Protection and Biocontrol Traits in .

Lysin motif (LysM) modules are approximately 50 amino acids long and bind to peptidoglycan, chitin and its derivatives. Certain LysM proteins in plant pathogenic and entomopathogenic fungi are shown to scavenge chitin oligosaccharides and thereby dampen host defense reactions. Other LysM proteins can protect the fungal cell wall against hydrolytic enzymes. In this study, we investigated the biological function of LysM proteins in the mycoparasitic fungus . The . genome contained three genes coding for LysM-containing proteins and gene expression analysis revealed that and were induced during mycoparasitic interaction with and during colonization of wheat roots. was suppressed in germinating conidia, while was induced during growth in chitin or peptidoglycan-containing medium. Deletion of and resulted in mutants with increased levels of conidiation and conidial germination, but reduced ability to control plant diseases caused by . and . The Δ strain showed a distinct, accelerated mycelial disintegration phenotype accompanied by reduced biomass production and hyphal protection against hydrolytic enzymes including chitinases, suggesting a role of LYSM2 in hyphal protection against chitinases. The Δ and ΔΔ strains displayed reduced ability to colonize wheat roots, while only ΔΔ failed to suppress expression of the wheat defense response genes and . Based on our data, we propose a role of LYSM1 as a regulator of fungal development and of LYSM2 in cell wall protection against endogenous hydrolytic enzymes, while both are required to suppress plant defense responses. Our findings expand the understanding of the role of LysM proteins in fungal-fungal interactions and biocontrol.