The Occurrence and Role of Substrate Adhesion Molecules (SAMs) in Plants

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Substrate adhesion molecules (SAMs) belong to a family of adhesive glycoproteins which occur in the extracellular matrix (ECM) of a variety of organisms. Vitronectin (VN) is a SAM that has been implicated in cell adhesion and migration. The PI's have established that a homolog to VN occurs in the primary cell wall of plants, and have evidence for its role in facilitating pollen tube extension in the style. The proposed research is a multi- faceted approach to understanding the expression, localization, and function of vitronectin-like molecules during plant development. The experiments proposed will specifically test the role of VN- like molecules during pollination. Immunocytochemical and fluorescence staining techniques will be used to examine the relationship between components of the cytoskeleton, VN-like molecules, and VN receptors (integrins) during pollen tube elongation and during shoot ontogeny. Synthetic peptides that are known to mediate adhesion of VN to its integrin will be used to determine their effect on pollen tube elongation in vivo and in vitro. cDNA clones that encode VN-like proteins will be isolated and characterized. The levels of VN RNA during plant development will be examined by RNA blot and in situ hybridizations. The role of VN-like proteins during plant development will be tested by overexpressing and underexpressing VN RNAs using chimeric gene constructs in transgenic plants.