Ripening of fruit and vegetables involves many biochemical and physiological changes that are both degradative and synthetic. Ethylene is a plant growth regulator closely associated with ripening and it triggers extensive changes in the physiology, biochemistry and gene expression. The project is studying genes and gene promoters involved in fruit ripening, and also the study of structure-function relations of proteins involved in ethylene biosynthesis and perception. The application potential of the isolated genes, gene promoters and novel inhibitors is also being investigated. Significant progress has been made to date and a large number of new genes and gene promoters involved in ripening have been isolated and studied. Many of the new genes isolated need further characterization to establish their function and to decide whether they can be used to control certain aspects of ripening. The promoter studies to date have revealed a number of fruit-specific ones that can be used to target antisense technology to fruit tissues. More detailed analysis of promoter sequences have revealed specific regions involved in ethylene responsiveness, fruit specificity and low oxygen responsiveness. Such information can eventually be used to design synthetic promoters having the desired properties. Enzyme studies have characterized different 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase isozymes and indicated that post-transcriptional regulation of ACC synthase activity may determine its activity. Novel ACC oxidase inhibitors were developed. Greenhouse-grown tomato plants treated with these inhibitors showed delayed fruit ripening. In plants ethylene is produced from S-adenosyl methionine (SAM) by the activity of two enzymes, (ie ACC synthase converts SAM to ACC and ACC is converted to ethylene by ACC oxidase).