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I am working jointly with Professors Jonathan Gershenzon and Ian Baldwin under the guidance of Meredith Schuman (Molecular Ecology)to evaluate the effects of sesquiterpene emission on Nicotiana attenuata's resistance to abiotic stress. Our plants are transformed with terpene synthase enzymes from maize that enable them to emit two 15-carbon volatile sesquiterpenes, (E)-ß-farnesene and (E)-alpha-bergamotene. Farnesene is not normally found in Nicotiana; bergamotene although found in herbivore-attacked wild type plants, is produced in 10-fold greater amounts by our transgenic lines. Based on the observed antioxidant effects of isoprene, the correlation between emission rate of sesquiterpenes and temperature in other plant species, and the high reactivity of sesquiterpenes with oxidants such as ozone, we hypothesize that these sesquiterpenes can act as antioxidants that increase plant tolerance of stresses such as heat, cold, drought, salinity, UV-B radiation, and ozone. To test the antioxidant hypothesis, I am comparing physiological responses of terpene-emitting and wild type plants under conditions of oxidative stress.
In addition to conducting abiotic stress experiments, I am collaborating with Boris Bonn (University of Frankfurt)to measure the potential impact of sesquiterpenes on aerosol formation. Aerosols form when plant-emitted volatile organic compounds interact with atmospheric pollutants and sunlight. These aerosols can then exert shading or warming effects, which have opposing influence on global climate warming. Sesquiterpenes react readily with ozone to form radicals that initiate particle formation. Although a correlation between plant volatile emission rate and particle formation has been shown at regional and continental scales, our transgenic sesquiterpene-emitting lines offer a unique opportunity to study the relationship between terpenes, ozone, and aerosols at the scale of a single plant. These studies explore the link between plant-scale processes and regional and global phenomena, and may clarify the selective pressures underlying volatile emission patterns.