Identification of Ca2+- Permeable Channel Genes in Guard Cells of Arabidopsis

The stomata pore surrounded by two guard cells in the surface of plant leaves allows CO₂ intake for photosynthesis and accounts for water loss. Multiple environmental and hormone stimuli, including ABA/drought stress, CO₂ and light, trigger stomata movement mediated by cytosolic Ca²⁺ oscillation and increases, which result from Ca²⁺ influx through inward Ca²⁺ channels in the plasma membrane of guard cells. However, the identity of the inward Ca²⁺ channels is still largely unknown. Here, we report the identification of putative Ca²⁺ channel genes highly expressed in guard cells of Arabidopsis. The proteins localize in the plasma membrane of N. Benthamiana protoplasts. The mutations in these channel genes impaired Ca²⁺ currents. This work suggests that the identified genes may encode Ca²⁺ permeable channels mediating Ca²⁺ influx in guard cells.