Novel Pectin Metabolizing Enzymes in Ripening Tomato Fruit Proposal: 0075074 Gerry Prody, PI
The focus of this project is the isolation and characterization two pectin hydrolyzing enzymes, rhamnogalacturonase and pectin acetylesterase, in ripening tomato fruits. The investigator plans to (1) trace the development of these enzyme activities as fruits begin to ripen and (2) begin purification of one or both of these proteins. If successful, this work will help to explain why fruit cell wall pectins are extensively solubilized before the more well-known polygalacturonase enzymes are produced during ripening.
Many biochemical changes occur as a fruit ripens. In this study, the investigator will look at one or more of these biochemical events during ripening of tomato fruit. As ripening occurs, the fruit turns red, develops flavor and aroma, and softens. One of the events involved in this softening is the breakdown of the cell walls in the fruit. Cell walls consist of complex arrays of sugars strung together and cross-linked to one another to make a fairly rigid assembly that protects the cell from damage and helps maintain the structure of plant tissues. As cell walls deteriorate, small chains of sugars, called oligosaccharides, are released. Some of these oligosaccharides may further stimulate the ripening process. In this study, the investigator will attempt to purify and characterize one or more of the enzymes involved in cell wall degradation during ripening. In particular, she will study an enzyme that degrades pectin, one of the carbohydrate components of plant cell walls. The enzyme, rhamnogalacturonase, cleaves bonds between the sugars rhamnose and galacturonic acid in pectin. This enzyme can serve to promote softening by degrading the pectin molecules and to regulate ripening by releasing stimulatory oligosaccharides. In addition to revealing important aspects of ripening-related biochemistry, this project has relevance to applied post-harvest biology. The most important problem that limits storage and transport of harvested fruits is premature softening. This project may identify important targets for technologies aimed at manipulation of fruit ripening. This is a POWRE project; the award will enable Dr.Prody to acquire the expertise necessary to establish this new line of research in her laboratory.
