Plants react to chemical and biological challenges from the environment with rapid changes in biochemical processes and gene expression. These responses cause plants to adapt by altering their chemical composition, their cell structure and how they grow. The set of immediate biochemical and genetic changes is termed the stress- or defense response, depending on whether the inciting agent is an organism or an environmental stress, such as excess light or an air pollutant. Ozone is a common air pollutant that affects plants in urban environments, the productivity of crop plants, and the health of forests at high altitudes. The present project focuses on the response of the model plant Arabidopsis to ozone. Leaf tissues respond very rapidly to ozone gas (even at levels reached in summer in large metropolitan areas) by producing bursts of highly reactive forms of oxygen, called reactive oxygen species. This response is called the "oxidative burst" and serves both a signaling function and as a cell-death trigger. Signals are transmitted within cells by a 3-component (heterotrimeric) G protein, as well as through other signaling pathways, including mitogen activated protein kinase cascades. The present research seeks to understand the role of the G protein in the oxidative stress response to ozone. The first objective is to ask how the components of the heterotrimeric G protein interact with each other, as well as with other proteins, during the ozone-induced stress response, and whether a subunit of the G protein is the direct target of activation in response to ozone. These experiments will be carried out using fluorescence resonance energy transfer, immunochemical methods, tandem affinity purification, and mass spectrometry. The second objective is to identify genes whose transcript abundance is regulated through signals transmitted through the G protein and those regulated through other signals using cDNA microarray expression profiling. Broader Impact: The importance of this work lies in the fact that the metabolic changes that comprise the stress response depress plant productivity; thereby decreasing crop yields. Understanding how plants respond to stress at the molecular level is one of the most important areas for the future of agriculture and sustainable development. Expanding knowledge about molecular and genetic networks activated by stress will open new knowledge-based avenues for enhancing the productivity of plants under suboptimal conditions, a central task in achieving global food security. In addition, this project will also provide training for several undergraduate and graduate students.
