A highly conserved metalloprotease effector enhances virulence in the maize anthracnose fungus <i>Colletotrichum graminicola</i>

<jats:title>Summary</jats:title><jats:p><jats:italic>Colletotrichum graminicola</jats:italic> causes maize anthracnose, an agronomically important disease with a worldwide distribution. We have identified a fungalysin metalloprotease (Cgfl) with a role in virulence. Transcriptional profiling experiments and live cell imaging show that <jats:italic>Cgfl</jats:italic> is specifically expressed during the biotrophic stage of infection. To determine whether <jats:italic>Cgfl</jats:italic> has a role in virulence, we obtained null mutants lacking <jats:italic>Cgfl</jats:italic> and performed pathogenicity and live microscopy assays. The appressorium morphology of the null mutants is normal, but they exhibit delayed development during the infection process on maize leaves and roots, showing that <jats:italic>Cgfl</jats:italic> has a role in virulence. <jats:italic>In vitro</jats:italic> chitinase activity assays of leaves infected with wild‐type and null mutant strains show that, in the absence of Cgfl, maize leaves exhibit increased chitinase activity. Phylogenetic analyses show that <jats:italic>Cgfl</jats:italic> is highly conserved in fungi. Similarity searches, phylogenetic analysis and transcriptional profiling show that <jats:italic>C. graminicola</jats:italic> encodes two LysM domain‐containing homologues of Ecp6, suggesting that this fungus employs both Cgfl‐mediated and LysM protein‐mediated strategies to control chitin signalling.</jats:p>