Stomata are pores on the leaf surface through which plants release oxygen and water vapor and take up carbon dioxide from the atmosphere. The size of the stomatal aperture (and hence the exchange of carbon dioxide and water vapor with the atmosphere) is controlled by specialized cells. These cells (called guard cells) change their shape in response to environmental conditions and are responsive to a range of signaling systems within the plant. The goal of this research is to understand how reactive oxygen species and changes in the reducing and oxidizing biochemistry in guard cells regulate an enzyme system (protein kinases) that controls stomatal movements in response to environmental cues. The function of stomata impacts the response of plants to environmental stress (including temperature and drought) and this research should lead to the rational breeding of improved (stress resistant) crop plants. The project will enable cross-disciplinary training of college and high school students (including women and members of underrepresented groups), in emerging fields of high-throughput science at the interface of biology and chemistry.
The project will use multiple approaches including molecular biology, biochemistry, genetics and analytical chemistry to tackle a critical problem in plant biology, i.e., the functions of reactive oxygen species and redox changes in regulating kinase activities and stomatal movements. The central hypothesis is that redox-dependent modification of cysteine residues in key protein kinases provides a versatile means of regulating kinase function in stomatal signaling. This hypothesis will be tested by pursuing two specific objectives: 1) To determine the cysteine modifications of Brassica napus sucrose non-fermenting related kinases. The experiments will enable comprehensive analysis of cysteine modifications in response to abscisic acid (a drought stress hormone) and a bacterial flagellin peptide that is involved in stomatal entrance of plant pathogens. 2) To determine cysteine modifications functional in stomatal movement and how they affect kinase phosphorylation. The experiments will identify the cysteine modifications essential for stomatal movement and analyze cysteine redox changes that regulate kinase activity. This project will reveal novel regulatory mechanisms underlying stomatal movements and will contribute to the emerging concept of redox modulation as a versatile mechanism by which cells regulate important signaling components and processes.
