Ca2+ Signaling in Plants: Molecular Mechanisms Underlying Cell Immune Response to Pathogens, Hormone Control of Plant Growth, and Stem Cell Signaling

Transient elevation of intracellular Ca2+ is the most common signal transduction mechanism present in any living organism. In plants, this cytosolic secondary messenger is involved in dozens of signaling pathways that orchestrate cellular response to environmental, developmental, and physiological cues. However, only recently have specific Ca2+ conducting proteins been associated with specific signal transduction pathways. Further, the molecular mechanisms that link cell membrane receptor perception of extracellular signals to Ca2+ elevations in the plant cell cytosol remain, essentially, unknown and/or the current models speculative and controversial. The molecular nature of plant Ca2+ channels and Ca2+ sensors that transmit the signal to downstream response systems are quite distinct from those present in animals. Work will be presented about this biological paradigm. Cyclic nucleotide gated Ca2+-conducting ion channels (CNGCs) were characterized using electrophysiological and biochemical analyses. Genetic tools were used to associate these channels with a number of signaling pathways. Studies were also undertaken to associate CNGCs with cell membrane receptors that are involved in their activation, thus linking receptor function with the signal transduction pathways controlled by these channels. Finally, some Ca2+ sensors (calmodulin and Ca2+-dependent protein kinases) and other molecular steps were identified as transmitters of these signals to control cell responses.