The proposed research will contribute to fundamental understanding of the role plant growth regulators or hormones play in mediating plant growth and differentiation. The objective is to clone and characterize the gene(s) for 1- aminocyclopropane-1-carboxylic acid (ACC) synthase in tomato. ACC synthase is the limiting enzyme in the biosynthesis of ethylene, a hormone whose level acts to coordinate the expression of many genes. Physiological studies indicate that this synthase is a highly regulated gene/enzyme that is induced by wounding, application of auxin or ethylene and plant development e.g. during fruit ripening. Its expression represents an important plant response to integrate the immediate environment with the plant's developmental programs. The project seeks to characterize the expression of this gene(s) in the various organs of the tomato plant, with a special focus in tomato fruit during ripening. ACC synthase activity, protein and RNA will be quantitated with gene specific probes, in order to determine what limits ACC synthase expression and to determine whether the various inducers and developmental programs use common and/or diverse mechanisms. Genetic studies indicate that only a small number of genes are required for the control of ACC synthase expression in fruit. As an initial test, two of these mutants rin and nor that do not undergo fruit ripening will be characterized. It will be determined whether these mutations have altered ACC synthase genes or whether they define other genes, possibly receptors that regulate, ACC synthase expression in tomato fruit.
