The Role of Signal Peptidase in the Pathogenic Association of the Anthracnose Stalk Rot Fungus Colletotrichum Graminicola with Maize

The program priority that will be addressed is priority 1: "Elucidation of molecular mechanisms of disease and resistance interactions between microbial plant pathogens and their host plants." Maize is the most valuable crop in the United States. Fungal stalk rot is one of the most serious diseases of maize. We used a random mutagenesis approach to identify a gene essential for pathogenicity in the hemibiotrophic stalk rot pathogen Colletotrichum graminicola. The gene (Cpr1) is a conserved component of the endoplasmic reticulum (ER)-localized signal peptidase. The proposed research will test the novel hypothesis that Cpr1 is up-regulated posttranscriptionally in response to ER stress and the unfolded protein response during biotrophic establishment, and that it has a specific and essential role in pathogenicity-related secretion through its interaction with other proteins in the signal peptidase complex. There has been a lot of interest in the roles of individual secreted effector proteins in phytopathogenic fungi, but we believe this proposal is unique in investigating the control of secretion itself is an important virulence factor. We can study the role of ER stress and UPR during both biotrophy and necrotrophy/rot in C. graminicola, thus our work may have broader applications for other fungal pathogens of both types. We will use cytological, molecular, and biochemical protocols to study the structure of the signal peptidase, regulation of secretory genes, and processing and transport of secreted proteins in mutant and wild type strains under ER stress in vitro and during biotrophic and necrotrophic development in planta.