This laboratory has identified a gene that appears to encode a novel class of receptors in plants. The molecular architecture of this putative plant cell receptor is reminiscent of the receptor tyrosine kinases (e.g. epidermal growth factor receptor, insulin and insulin-like receptors, and platelet-derived growth factor receptor) known in animals. It consists of a cytoplasmic domain that is homologous to the serine/threonine-specific protein kinases. This kinase domain is linked, via a membrane-spanning stretch of amino acids, to an extracellular domain. This extracellular domain is related to S-locus (self-incompatibility) glycoproteins of Brassica, which are involved in pollen recognition. The newly isolated gene may represent a prototype of an entire class of plant cell receptors with protein kinase activity. The proposed research will establish the biochemical properties of the maize putative protein kinase and obtain a clear understanding of its tissue, cellular, and subcellular distribution. All cells bear on their surfaces molecular receptors that sense external information and relay this information into the cell. The subject of the proposed research is a newly identified receptor- like molecule in plants. The structure of this molecule resembles that of some important growth factor receptors of animal cells. The goal of this project is to study the biochemistry and distribution of this molecule in plants. Molecules of this type could be of profound importance in developmental and environmental responses and cell to cell signaling in higher plants.