Ca2+ is involved in muscarine-acetylcholine-receptor-mediated acetylcholine signal transduction in guard cells of Vicia faba L

Abstract

Acetylcholine (ACh) is an important neurochemical transmitter in animals; it also exists in plants and plays a significant role in various kinds of physiological functions in plants. ACh has been known to induce the stomatal opening. By monitoring the changes of cytosolic Ca 2+ with fluorescent probe Fluo-3 AM under the confocal microscopy, we found that exogenous ACh increased cytosolic Ca 2+ concentration of guard cells of Vicia faba L. Muscarine, an agonist of muscarine acetylcholine receptor (mAChR), could do so as well. In contrast, atropine, the antagonist of mAChR abolished the ability of ACh to increase Ca2+ in guard cells. This mechanism is similar to mAChR in animals. When EGTA was used to chelate Ca 2+ or ruthenium red to block Ca 2+ released from vacuole respectively, the results showed that the increased cytosolic Ca 2+ mainly come from intracellular Ca 2+ store. The evidence supports that Ca 2+ is involved in guard-cell response to ACh and that Ca 2+ signal is coupled to mAChRs in ACh signal transduction in guard cells.