It is proposed that calcium acts as a messenger in the response of plant tissues to signals such as hormones (auxin and cytokinin) and light. The overall objective of Dr. Poovaiah's research is to understand this role of calcium ions in plants. Recent studies have demonstrated the presence of calcium- dependent and calmodulin-dependent protein phosphorylation in a number of plant systems. The focus of the next experiments in this study will be calcium- and calmodulin-promoted protein kinases and their substrates, with a view toward understanding their physiological roles. Two goals will be pursued: 1. Calcium-regulated protein kinases and their substrates will be isolated, characterized, and localized by immunocytochemistry. 2. The substrates for calcium- and calmodulin-dependent protein kinases will be identified and characterized in order to obtain more insight into the physiological significance of calcium and calmodulin-dependent protein phosphorylation. Hormones, light, and gravity control diverse physiological processes throughout the life cycle of plants. How the cell senses these signals and converts them into a response is poorly understood and is a subject of great interest. Recent investigations support the concept that some hormone and light dependent changes in plants involve calcium as a messenger. The proposed research is directed toward understanding this function of calcium. The results of these studies will advance our knowledge of both the cellular functions of calcium and the molecular mechanisms involved in the transduction of hormone and light signals in plants.
