A cell surface receptor mediates extracellular Ca(2+) sensing in guard cells.
Extracellular Ca(2+) (Ca(2+)(o)) is required for various physiological and developmental processes in animals and plants. In response to varied Ca(2+)(o) levels, plants maintain relatively constant internal Ca(2+) content, suggesting a precise regulatory mechanism for Ca(2+) homeostasis. However, little is known about how plants monitor Ca(2+)(o) status and whether Ca(2+)(o)-sensing receptors exist. The effects of Ca(2+)(o) on guard cells in promoting stomatal closure by inducing increases in the concentration of cytosolic Ca(2+) ([Ca(2+)](i)) provide a clue to Ca(2+)(o) sensing. Here we have used a functional screening assay in mammalian cells to isolate an Arabidopsis complementary DNA clone encoding a Ca(2+)-sensing receptor, CAS. CAS is localized to the plasma membrane, exhibits low-affinity/high-capacity Ca(2+) binding, and mediates Ca(2+)(o)-induced [Ca(2+)](i) increases. CAS is expressed predominantly in the shoot, including guard cells. Repression of CAS disrupts Ca(2+)(o) signalling in guard cells, and impairs bolting (swift upward growth at the transition to seed production) in response to Ca(2+) deficiency, so we conclude that CAS may be a primary transducer of Ca(2+)(o) in plants.
Han
Shengcheng
S
Department of Biology, Developmental, Cell, and Molecular Biology Group, Duke University, Durham, North Carolina 27708, USA.
Tang
Ruhang
R
Anderson
Lisa K
LK
Woerner
Todd E
TE
Pei
Zhen-Ming
ZM
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000166:cytology* / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D002118:Calcium / Q000172:deficiency / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D003001:Cloning, Molecular; D020869:Gene Expression Profiling; D017343:Genes, Plant / Q000235:genetics; D006706:Homeostasis; D006801:Humans; D008969:Molecular Sequence Data; D021381:Protein Transport; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D044169:Receptors, Calcium-Sensing; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D029681:Arabidopsis Proteins; D012333:RNA, Messenger; D044169:Receptors, Calcium-Sensing; D011956:Receptors, Cell Surface; D002118:Calcium