THE GENERATION OF Ca2+ SIGNALS IN PLANTS

▪ Abstract The calcium ion is firmly established as a ubiquitous intracellular second messenger in plants. At their simplest, Ca 2+ -based signaling systems are composed of a receptor, a system for generating the increase in [Ca 2+ ] cyt , downstream components that are capable of reacting to the increase in [Ca 2+ ] cyt , and other cellular systems responsible for returning [Ca 2+ ] cyt to its prestimulus level. Here we review the various mechanisms responsible for generating the stimulus-induced increases in [Ca 2+ ] cyt known as Ca 2+ signals. We focus particularly on the mechanisms responsible for generating [Ca 2+ ] cyt oscillations and transients and use Nod Factor signaling in legume root hairs and stimulus-response coupling in guard cells to assess the physiological significance of these classes of Ca 2+ signals.