The ACA4 gene of Arabidopsis encodes a vacuolar membrane calcium pump that improves salt tolerance in yeast.
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.
Geisler
M
M
Department of Plant Biology, The Royal Veterinary and Agricultural University, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark.
Frangne
N
N
Gomès
E
E
Martinoia
E
E
Palmgren
M G
MG
D000222:Adaptation, Physiological / Q000187:drug effects; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics*; D029681:Arabidopsis Proteins; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D005816:Genetic Complementation Test; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D011189:Potassium Chloride / Q000494:pharmacology; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development; D012492:Salts / Q000494:pharmacology*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D012965:Sodium Chloride / Q000494:pharmacology; D014018:Tissue Distribution; D014617:Vacuoles / Q000201:enzymology*
D029681:Arabidopsis Proteins; D002147:Calmodulin; D018076:DNA, Complementary; D007527:Isoenzymes; D012333:RNA, Messenger; D012492:Salts; D012965:Sodium Chloride; D011189:Potassium Chloride; C419649:ACA4 protein, Arabidopsis; D000252:Calcium-Transporting ATPases; D002118:Calcium