Figure 8.

A Model for CAU1/CAS-Mediated [Ca²⁺]_o Signaling in Stomatal Closure.

Elevated [Ca²⁺]_o reduces the CAU1 association with the CAS promoter, which consequently decreases histone methylation of the CAS chromatin and lifts the repression of CAS. The resulting upregulation of CAS further evokes cytosolic Ca²⁺ ([Ca²⁺]_cyt) and the subsequent stomatal closure (Tang et al., 2007), possibly through IP3 (Tang et al., 2007), ROS (Wang et al., 2012a), or mechanisms that are yet to be identified. Stomatal closure decreases the transpiration rate, leading to feedback inhibition of Ca²⁺ translocation to the plant aerial parts. Thus, a dynamic synchronization between [Ca²⁺]_o and stomatal closure is established and functions to mediate plant adaptation to the environment. The question marks and dashed lines represent possible unidentified steps or steps that have been identified but are not shown here.