9417582 Pichersky Flower scents exert strong influence on plant reproductive success, and thus are crucial determinants of yield in fruit crops that require scent-seeking pollinators. However, the biosynthetic pathways of floral scents have scarcely been investigated on the biochemical, genetic and molecular levels. Dr. Pichersky proposes to study scent production in Clarkia, a genus of annual plants native to California. Clarkia breweri is the only species in the genus with floral scent; its flowers are visited mostly by hawkmoths. The odorless flowers of C. concinna, a closely related species from which C. breweri arose, are visited mostly by butterflies, whereas all other outcrossing Clarkia species are pollinated by bees. The investigator has identified two major pathways that contribute to the floral scent of C. breweri. One of these pathways, the subject of this propoal, results in the production of the monoterpenes linalool and linalool oxides. It has been shown that this pathway also operates in C. Concinna flowers as well, albeit at a greatly reduced level, and it therefore appears that the evolution of monoterpene emission in C. breweri has occurrred by up- regulating this pathway. To test this hypothesis, Dr. Pichersky and his colleagues have already developed an enzymatic assay for linalool synthase (LIS), the enzyme that catalyzes the formation of linalool, and have purified the protein. They will now develop a spectrophotometric assay for linalool epoxidae (LIE), the enzyme that catalyzes the formation of 6,7-linalool expoxide, an intermediate in the formation of linalool oxides. They will isolate and characterize the Lis and Lie genes from both Clarkia species and investigate the genetic and molecular control mechanisms that govern their expression and are responsible for the interspecific differences, using recombinant promoter - GUS reporter gene fusion and plant transforation and DNA-protein interaction assays. The cellular and subce llular localization of the enzymes will be determined using a combination of immunological techniques. The data obtained will increase our understanding of the biochemical and genetic control of flower scent production, and may lead to future ability to manipulate these traits in agronomically important plants.
