Elevation of Cytosolic Calcium in Guard Cells

Calcium ion (Ca2+) is a ubiquitous intracellular second messenger that regulates many cellular processes in plants as well as in animals. Guard cells respond to environmental and internal stimuli, resulting in a change in a stomatal aperture. This signaling pathway employs Ca2+ as a second messenger in the guard cells. Hence, elevation of cytosolic free Ca2+ concentration ([Ca2+]cyt) can be observed in guard cells treated with phytohormones such as abscisic acid and methyl jasmonate. Several other second messengers including cyclic ADP-ribose, inositol 1,4,5-trisphosphate, and myo-inositol hexakisphosphate are involved in the [Ca2+]cyt elevation in the guard cells. Moreover, several methods have been developed to observe the [Ca2+]cyt elevation in the guard cells. In this mini-review, we briefly introduce the roles and regulation of the transient [Ca2+]cyt elevation in the guard cells and the methods to monitor the [Ca2+]cyt.