Elevated Atmospheric CO2 and Cytosolic Control of Leaf Isoprene Biogenesis

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Intellectual MeritThe emission of isoprene from the leaves of trees causes photochemical reactions in the lower atmosphere that lead to many important environmental consequences. For example, isoprene from trees contributes to the formation of tropospheric ozone pollution, an increase in the concentration of atmospheric methane, and the production of nitrogenous compounds that can harm human health and plant productivity. Past studies show that isoprene emissions from trees are inhibited by elevated atmospheric carbon dioxide (CO2) concentrations. This inihibition leads to the hypothesis that in the future, as the atmospheric CO2 concentration increases, the emission of isoprene from forest ecosystems will decrease. Current understanding of the physiological processes that control isoprene emission at elevated CO2 is inadequate for accurately predicting future isoprene emissions from forests. This project will improve our understanding of the processes that control isoprene emissions from leaves in an atmosphere of elevated CO2, and will focus on processes at the cellular level. The project tests the hypothesis that isoprene emissions are inhibited at elevated CO2 because of competition between the chloroplasts and the cytosol of the cell for carbon substrates. Experiments will focus on the response of the enzymes and processes known to be sensitive to increases in atmospheric CO2. The research will utilize advanced instrumentation and technologies to test the hypothesis that elevated atmospheric CO2 causes partial depletion of a chloroplast substrate needed for isoprene biosynthesis. Advanced instrumentation and technologies include proton transfer reaction mass spectrometry, and advanced biochemical techniques in enzyme purification and characterization. The research will be conducted with cottonwood (Populus) trees that are genetically transformed specifically for this study. Broader ImpactsThe studies will provide training opportunities for a postdoctoral student, and two graduate students. The project will also catalyze development of a unique course entitled, "Forest Biotechnology and the Environment." The research will foster the collaborative relationship between those at the University of Colorado, and those working with Professor Heinz Rennenberg at the Universitat Freiburg, Germany. Professors Monson and Fall participate in the Cooperative Institute for Research in Environmental Science (CIRES), that stimulates interdisciplinary research within and between the University of Colorado and the National Oceanic and Atmospheric Administration (NOAA).