Guard cell ABA and CO2 signaling network updates and Ca2+ sensor priming hypothesis.

Stomatal pores in the epidermis of plants enable gas exchange between plants and the atmosphere, a process vital to plant life. Pairs of specialized guard cells surround and control stomatal apertures. Stomatal closing is induced by abscisic acid (ABA) and elevated CO(2) concentrations. Recent advances have been made in understanding ABA signaling and in characterizing CO(2) transduction mechanisms and CO(2) signaling mutants. In addition, models of Ca(2+)-dependent and Ca(2+)-independent signaling in guard cells have been developed and a new hypothesis has been formed in which physiological stimuli are proposed to prime Ca(2+) sensors, thus enabling specificity in Ca(2+)-dependent signal transduction.