The goal of the proposed project is to understand the metabolic controls on proline and putrescine synthesis in two plants (pea, oat) that exhibit fundamentally different responses to osmotic stress. Oat leaves accumulate putrescine to high levels, while proline accumulation is minimal. Pea leaves accumulate proline, but very little putrescine. Radiolabeled precursors and inhibitors of the arginine, putrescine and proline biosynthetic pathways will be used to investigate basic metabolic responses to stress in these plants. Cellular and molecular mechanisms regulating the activities of the arginine decarboxylase (ADC), which catalyzes the first reaction in the putrescine biosynthetic pathway, and pyrroline-5-carboxylate reductase (P5CR), an enzyme which carries out the final step in proline biosynthesis will be investigated. There is evidence that the activities of both ADC and P5CR are stress-inducible and these enzymes may play important roles in the regulation of proline and putrescine accumulation in response to stress. A more complete understanding of stress-dependent changes in these pathways may yield new insights into basic underlying stress adaptation strategies used by plants and may lead to the development of cultivars with improved stress tolerance characteristics.
