Abstract
Several lines of evidence suggest that regulation of intracellular Ca(2+) levels is crucial for adaptation of plants to environmental stress. We have cloned and characterized Arabidopsis auto-inhibited Ca(2+)-ATPase, isoform 4 (ACA4), a calmodulin-regulated Ca(2+)-ATPase. Confocal laser scanning data of a green fluorescent protein-tagged version of ACA4 as well as western-blot analysis of microsomal fractions obtained from two-phase partitioning and Suc density gradient centrifugation suggest that ACA4 is localized to small vacuoles. The N terminus of ACA4 contains an auto-inhibitory domain with a binding site for calmodulin as demonstrated through calmodulin-binding studies and complementation experiments using the calcium transport yeast mutant K616. ACA4 and PMC1, the yeast vacuolar Ca(2+)-ATPase, conferred protection against osmotic stress such as high NaCl, KCl, and mannitol when expressed in the K616 strain. An N-terminally modified form of ACA4 specifically conferred increased NaCl tolerance, whereas full-length ATPase had less effect.
Publication types
-
Research Support, Non-U.S. Gov't
MeSH terms
-
Adaptation, Physiological / drug effects
-
Amino Acid Sequence
-
Arabidopsis / enzymology
-
Arabidopsis / genetics*
-
Arabidopsis Proteins*
-
Binding Sites
-
Calcium / metabolism
-
Calcium / pharmacology
-
Calcium-Transporting ATPases / chemistry
-
Calcium-Transporting ATPases / genetics*
-
Calcium-Transporting ATPases / metabolism
-
Calmodulin / metabolism
-
DNA, Complementary / chemistry
-
DNA, Complementary / genetics
-
Gene Expression Regulation, Enzymologic
-
Gene Expression Regulation, Plant
-
Genetic Complementation Test
-
Isoenzymes / genetics
-
Isoenzymes / metabolism
-
Molecular Sequence Data
-
Mutation
-
Potassium Chloride / pharmacology
-
RNA, Messenger / drug effects
-
RNA, Messenger / genetics
-
RNA, Messenger / metabolism
-
Saccharomyces cerevisiae / drug effects*
-
Saccharomyces cerevisiae / genetics
-
Saccharomyces cerevisiae / growth & development
-
Salts / pharmacology*
-
Sequence Alignment
-
Sequence Analysis, DNA
-
Sequence Homology, Amino Acid
-
Signal Transduction
-
Sodium Chloride / pharmacology
-
Tissue Distribution
-
Vacuoles / enzymology*
Substances
-
Arabidopsis Proteins
-
Calmodulin
-
DNA, Complementary
-
Isoenzymes
-
RNA, Messenger
-
Salts
-
Sodium Chloride
-
Potassium Chloride
-
ACA4 protein, Arabidopsis
-
Calcium-Transporting ATPases
-
Calcium