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 CO2 concentrations. Recent advances have been made in understanding ABA signaling and in characterizing CO2 transduction mechanisms and CO2 signaling mutants. In addition, models of Ca2+-dependent and Ca2+-independent signaling in guard cells have been developed and a new hypothesis has been formed in which physiological stimuli are proposed to prime Ca2+ sensors, thus enabling specificity in Ca2+-dependent signal transduction.