Perception of environmental conditions and initiation of appropriate responses to these conditions is crucial for survival of all organisms. Additionally, individual cells of multicellular organisms must detect and respond to signals which coordinate the behavior and physiology of the whole organism. In contrast to the case for animal systems, little is known about transduction pathways coupling signals to cellular responses in plants. The coupling of light reception to leaflet movement in the tropical legume Samanea saman and of environmental stress to deflagellation in the unicellular alga Chlamydomonas reinhardtii are signal response systems that appear to involve calcium. We hypothesize that inositolphospholipid and phosphatidylcholine turnover which produces inositol phosphates, lysophosphatidylcholine and diacylglycerol, and which results in mobilization of cellular calcium and protein phosphorylation mediates these responses. To elucidate the specific role of phospholipid turnover in these systems we will: i.) correlate temporally changes in inositolphospholipid and phosphatidylcholine metabolism and intracellular calcium levels with signal reception and cell response, ii.) examine effects of agents that perturb the functioning of inositolphospholipid metabolism and calcium homeostasis on physiological responses to signals, and iii.) purify and characterize the putative regulatory enzyme phospholipase C with the aim of understanding its role in plant signal transduction.
