The Role of Terpene Synthases in Floral Scent Emission in Arabidopsis thaliana and Related Species

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Arabidopsis thaliana is the most important plant model organism, and the sequence of its entire complement of genes is now known. Although it is generally believed that A. thaliana flowers mostly self-pollinate, we have discovered that the flowers emit scent volatiles of the terpene class of compounds, and previous reports do suggest that an undetermined level of cross-pollination does occur in nature. The A. thaliana genome has 33 genes with homology to known terpene synthases (TPSs), and we have shown that under normal conditions, five of these genes are expressed exclusively in flowers, and 14 more are expressed in flowers as well as in some other tissues. In this project, Dr. Pichersky's lab will characterize the floral scent of A. thaliana plants from different environments, characterize the activity of the enzymes encoded by all the flower-expressed TPS genes, perform a detailed examination of the tissue-specific expression of these TPS genes throughout the plant, identify insect visitors to A. thaliana flowers, and estimate the level of cross-pollination caused by such visits. Related species that are more noticeably scented will also be compared. This project is an interdisciplinary investigation of the biosynthesis of floral scent and its effect on the success of cross-pollination, encompassing methods from molecular biology to biochemistry to ecology. The results will provide detailed understanding of an important plant life trait that has hitherto been little understood. This new knowledge will also be highly applicable to crop plants, many of which depend on cross-pollination for seed and fruit set. Knowing how scent genes are activated in the A. thaliana model system will facilitate the discovery and manipulation of scent genes in important crop plants to enhance scent production and attract beneficial pollinators. Finally, the project will provide excellent interdisciplinary training and education for graduate and undergraduate students both in the PI's lab and in formal courses, and the PI will continue to disseminate the results to the general public in addition to reports in scientific journals.