Functional Analysis of Plant Carotenoid Dioxygenases

University Of Florida, Gainesville FL

Investigators

Abstract

This project addresses the functions of a class of enzymes known as carotenoid cleaving dioxygenases (CCDs). These enzymes metabolize carotenoids, creating a vast array of economically important molecules. Some of the products of these enzymes, called apocarotenoids, also have biological activity in plants and animals. Important apocarotenoids include retinoids in animals, abscisic acid in plants, the major colorant and flavor compound in saffron, and major scent volatiles in roses. The investigators have focused on four CCD enzymes (CCD1, CCD4, CCD7 and CCD8). Two of the enzymes, CCD1 and CCD4 appear to function in synthesis of flavor and scent volatiles. They also have as yet undefined roles in carotenoid turnover. Loss of either of these two gene products significantly increases the carotenoid content of seeds. The project will address the functions of these two enzymes as it relates to carotenoid content with the potential to enhance the nutritional composition of some foods. Techniques for characterizing the biochemical activity of CCD1 were developed during the prior funding period. These techniques will now be applied to biochemical characterization of CCD4. CCD7 and CCD8 act coordinately to synthesize an as yet unidentified novel plant hormone that regulates the ability of the plant to make branches. A major goal of the investigators, together with collaborators, is to identify the biologically active compound synthesized by the CCD7/CCD8. In addition to isolation of the hormone from plant tissue, the biochemical properties and substrate preferences of CCD7 and CCD8 will be determined. A related goal is to characterize the natural variance within maize populations of CCD7 and CCD8. Broader Impacts: The project is expected to provide fundamental insights into the functions of the CCD enzymes. Understanding the roles of these enzymes in vivo has great potential to improve both flavor and nutrition of foods, especially in the developing world. The project also has the potential to identify an entirely new class of plant hormones that regulate plant architecture. This research is a platform to educate undergraduate and graduate students, including minority students from Fort Valley State University, an 1890 Land-Grant University.