Isolation of Genes Mediating Cell-Surface Induction of Infection Structures

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The overall objective of the proposed research is to identify genes that regulate the development of highly specialized structures (appressoria) that are essential for rice plant infection by Magnaporthe grisea. M. grisea is ideal for these studies since infection structure formation can be induced in vitro, the fungus is highly amenable to both Mendelian and molecular genetic manipulation and as a plant pathogen it is of major importance. Infection structure formation is initiated following conidia germination on certain hydrophobic substrata. After limited extension, the germ tube tip swells to form a dome shaped attachment structure, the appressorium. An infection hyphae emerges from the appressorium at the contact interface and penetrates directly. Dr. Dean has previously identified two genes, mif23 and mif29, that are specifically expressed during infection structure formation. Since these genes respond to environmental signals, he proposes to fuse promoters to selectable markers in order to obtain mutations in regulatory pathway genes. He has also identified mutants blocked at various stages of development and propose to search for more. The affected genes will be genetically mapped and functionally complemented by DNA transformation. Complementing DNA will be recovered and the genes cloned and characterized. The identification of these genes is paramount to understanding and controlling the mechanism(s) regulating cell surface interactions and fungal infection of plants.