AUTHOR=Dubey Mukesh , Vélëz Heriberto , Broberg Martin , Jensen Dan Funck , Karlsson Magnus 

TITLE=LysM Proteins Regulate Fungal Development and Contribute to Hyphal Protection and Biocontrol Traits in Clonostachys rosea

JOURNAL=Frontiers in Microbiology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2020.00679

DOI=10.3389/fmicb.2020.00679

ISSN=1664-302X

ABSTRACT=<p>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 <italic>Clonostachys rosea</italic>. The <italic>C</italic>. <italic>rosea</italic> genome contained three genes coding for LysM-containing proteins and gene expression analysis revealed that <italic>lysm1</italic> and <italic>lysm2</italic> were induced during mycoparasitic interaction with <italic>Fusarium graminearum</italic> and during colonization of wheat roots. <italic>Lysm1</italic> was suppressed in germinating conidia, while <italic>lysm2</italic> was induced during growth in chitin or peptidoglycan-containing medium. Deletion of <italic>lysm1</italic> and <italic>lysm2</italic> resulted in mutants with increased levels of conidiation and conidial germination, but reduced ability to control plant diseases caused by <italic>F</italic>. <italic>graminearum</italic> and <italic>Botrytis cinerea</italic>. The Δ<italic>lysm2</italic> 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<italic>lysm2</italic> and Δ<italic>lysm1</italic>Δ<italic>lysm2</italic> strains displayed reduced ability to colonize wheat roots, while only Δ<italic>lysm1</italic>Δ<italic>lysm2</italic> failed to suppress expression of the wheat defense response genes <italic>PR1</italic> and <italic>PR4</italic>. 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.</p>