Characterization of CAX-like genes in plants: implications for functional diversity.
Transporter-mediated Ca(2+) efflux from the cytoplasm is an important component of plant signal transduction. To elucidate the diversity and role of Ca(2+)/H(+) in controlling plant cytosolic Ca(2+) concentrations, homologs of CAX (for calcium exchanger) genes were cloned from Zea mays and Arabidopsis thaliana cDNA libraries. The A. thaliana homolog of CAX (AtHCX1) is 77% identical to CAX1 while the Z. mays homolog of CAX (ZmHCX1) is 64% identical to CAX1 in amino acid sequence. AtHCX1 transcripts appeared to be expressed in all tissues, and levels of AtHCX1 RNA increased after Ca(2+) or Na(+) treatment. When expressed in yeast mutants defective in vacuolar Ca(2+) uptake, ZmHCX1 and AtHCX1 failed to suppress the Ca(2+) sensitivity of these strains. These results imply that CAX-like genes may have functions in plant ion homeostasis that differ from those of previously characterized CAX genes.
Shigaki
T
T
Baylor College of Medicine, Plant Physiology Group, USDA/ARS Children's Nutrition Research Center, 1100 Bates St., Houston, TX 77030, USA.
Hirschi
K
K
D000595:Amino Acid Sequence; D017920:Antiporters / Q000235:genetics* / Q000502:physiology; D017360:Arabidopsis / Q000235:genetics*; D015152:Blotting, Northern; D002135:Calcium-Binding Proteins / Q000235:genetics* / Q000502:physiology; D027682:Cation Transport Proteins; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics*; D005816:Genetic Complementation Test; D014644:Genetic Variation; D008969:Molecular Sequence Data; D009154:Mutation; D010802:Phylogeny; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution; D003313:Zea mays / Q000235:genetics*
D017920:Antiporters; D002135:Calcium-Binding Proteins; D027682:Cation Transport Proteins; D018076:DNA, Complementary; D018749:RNA, Plant; C027614:calcium-hydrogen antiporters