9318544 Kolattukudy Plant cuticle, the outermost layer of plants, plays a significant role in the interaction of plants with the environment including pathogenic fungi. The structural polymers of plant defensive barriers, cutin and suberin, will be examined using a new technology, atomic force microscopy, that gives images at molecular dimensions and thus could directly reveal for the first time the molecular architecture of these complex polymers. The nature of the enzymes and genes involved in the biosynthesis of the cuticular components will be elucidated by direct isolation of the enzymes and by cloning genes uniquely expressed in the epidermis, the site of synthesis of the cuticular components. Molecular mechanisms involved in the fungal penetration into plants will be elucidated. How cuticular components and the ripening hormone, ethylene, trigger germination and differentiation of fungal conidia to form appressorium, the infection structure, will be studied by elucidating the structure, function and regulation of expression of the unique fungal genes regulated by the plant signals. How the unique cutin monomer acids trigger fungal cutinase gene expression will be studied by isolating the transcription factors that bind the promoter elements and by cloning the kinases that activate the transcription factor binding. After breaching the cuticular barrier the fungal pathogen penetrates the pectinaceous barriers using pectin degrading enzymes including pectate lyase. The role of regulation of expression of the various members of the family of fungal lyase genes in pathogenesis will be studied by elucidating the conditions under which each gene is expressed and by assessing the effect of inhibition of expression of the genes by gene disruption and antisense on the virulence of the pathogen. The results of the proposed studies will help to elucidate the basic mechanisms involved in the interaction of pathogenic fungi with the defensive barriers of pl ants. Manipulation of these interactions could provide new approaches to plant protection. ***
