Thomas D. Sharkey, PhD - US grants

Isoprene is emitted from many plants, especially trees such as oaks and aspens. The amount emitted is very large and has significant effects on atmospheric chemistry. On the other hand, isoprene can serve as a chemical feedstock and is already being exploited commercially. To understand the function and regulation of isoprene emission from plants, experiments will be undertaken to test and determine how plants that emit isoprene are affected by this emission. Novel optical methods will be used to measure leakiness of photosynthetic membranes and determine how isoprene affects this leakiness. The effect of isoprene on other membrane functions, such as formation of lipid drops and possible cell death signals will also be measured. Experiments to test the regulation will focus on measuring enzyme activity with and without possible inhibitors and measuring changes in enzyme activities in relation to changes in isoprene emission rate. The results of the work will be useful for understanding isoprene emission, one of the most important chemical interactions between the biosphere and atmosphere. This information may aid decisions such as whether to alter what trees are planted and will aid in predicting when air pollution episodes are likely to be exacerbated by isoprene. The work may also be useful in engineering other organisms to make isoprene so that it can be used as a replacement for petroleum. This research will involve many students including undergraduates recruited to a summer program designed to increase participation in science by members of underrepresented groups.

Many plants, especially trees, make a hydrocarbon called isoprene which is the single biggest source of hydrocarbon emitted to the atmosphere. Atmospheric hydrocarbons can have a significant effect on atmospheric pollution. On the other hand, isoprene appears to give plants the ability to resist some stresses such as rapid increases in temperature and ozone. Because only some trees make isoprene it is believed that there is a fine balance between the advantages and costs to plants to making it. This research specifically tests the benefits and costs of isoprene emission from plants. This will provide information about the utility of isoprene emission and help determine whether breeding and engineering programs should target increasing or decreasing isoprene emission from crops. Summer research internships for undergraduate students will train students in modern plant research, help them identify their academic goals and prepare them to join a future workforce that is diverse and globally competitive. Public scientific literacy will be promoted by participation in ?Fascination of Plants Day? and the Michigan State University Science Festival, annual events organized to inform the general public about science and its uses in everyday life.

Isoprene emission from plants is the biggest source of volatile hydrocarbon in the atmosphere. It breaks down rapidly and, when there are nitrogen oxides present, it can contribute to ozone, particulates, and formaldehyde in the atmosphere. A comprehensive understanding of the role of isoprene in plant function has not yet emerged. The evolution of the capacity for isoprene emission is enigmatic, it appears to have evolved multiple times and the capacity for isoprene emission also seems to have been lost many times. The proposed work will systematically evaluate the evolution of the capacity for isoprene emission in plants. The relatively frequent gain and loss of isoprene emission and its scattered distribution among land plants indicate that the trait is constantly in an evolutionary balancing act, enhancing plant resilience and fitness but at some cost, thereby responding to varying evolutionary constraints. Isoprene appears to help plants tolerate some types of high temperature stress and oxidative damage. Temperature and oxidative stress effects in the presence and absence of isoprene emission will be studied in three species, Arabidopsis engineered to make isoprene, tobacco engineered to make isoprene, and poplar engineered to stop making isoprene. In addition to temperature and oxidative stress, salt stress, water stress, jasmonic acid signaling, and necrotrophic pathogen resistance will be explored.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.