Molecular characterization of a Stagonospora nodorum lipase gene LIP1

A triglyceride lipase gene (LIP1) was cloned from Stagonospora nodorum, the causal agent of wheat glume blotch. LIP1 encodes a 561 amino acid preproprotein with a predicted N-terminal signal peptide. Its expression was up-regulated during plant infection and in culture media supplemented with saturated fatty glycerides. The recombinant Lip1 protein possessed lipolytic activity against a broad range of lipid substrates. When applied to wheat leaves, recombinant Lip1 decreased the hydrophobicity of the leaf surface, probably by liquefaction of epicuticular wax. Pretreatment of wheat leaves with Lip1 decreased the rate of conidial adhesion from 69.5% to 22.7% and from 58.9% to 28.4% in two independent assays based on different protocols. LIP1 replacement strains showed decreased lipolytic activity on culture media relative to the wild-type strain, and adhesion of the conidia to the wheat leaf surface was impaired in the gene replacement strains. In two experiments, adhesion rates were 54.3% and 41.6% in the LIP1 replacement strains, as opposed to 77.7% and 66.6%, respectively, in the wild-type. Collectively, the data demonstrate that the secreted lipase Lip1 is important for the adhesion of S. nodorum infection to wheat leaves.