Poster: Stomatal Physiology

Abs # 392: A receptor for extracellular calcium-sensing in Arabidopsis guard cells

Presenter:	Pei, Zhen-Ming , zpei@duke.edu
Authors	Pei, Zhen-Ming  (A)   Han, Shengcheng  (A)   Tang, Ruhang  (A)   Anderson, Lisa K (A)
Affiliations:	(A): Duke University

Calcium plays a pivotal role in various physiological and developmental processes in plants. In plant tissues, a high proportion of the total Ca²⁺ is often located in the cell wall and at the exterior surface of the plasma membrane, being important for the stability of the wall and the membrane as well as cell integrity. The role of extracellular Ca²⁺ (Ca²⁺_o) that serves as Ca²⁺ stores for the changes of cytosolic free Ca²⁺, a second messenger, in response to environmental and developmental cures is now well known, but less understood is whether Ca²⁺_o can also function as a primary messenger in plants. The effects of Ca²⁺_o on guard cells in promoting stomatal closure via triggering cytosolic Ca²⁺ increases and oscillations provide a suitable system for dissecting Ca²⁺_o signal transduction pathway in plants. We have used a functional screening assay in mammalian cells, and isolated an Arabidopsis cDNA clone encoding a Ca²⁺_o-sensing receptor (CAS). CAS is predominantly expressed in the shoot, including guard cells, and localized to the plasma membrane. Elimination of CAS expression disrupts Ca²⁺_o-induced cytosolic Ca²⁺ increase and stomatal closure. These data indicate that CAS may be a primary transducer of Ca²⁺_o in Arabidopsis.