Two additional type IIA Ca(2+)-ATPases are expressed in Arabidopsis thaliana: evidence that type IIA sub-groups exist

High affinity Ca(2+)-ATPases play a central role in calcium homeostasis by catalysing the active efflux of calcium from the cytoplasm. This study reports the identification of two additional type IIA (SERCA-type) Ca(2+)-ATPases from Arabidopsis (AtECA2 and AtECA3), and describes the detailed sequence analysis of these genes in comparison with AtECA1 and other plant and animal Ca(2+)-ATPases. Southern analysis suggests that each of these genes is present as a single copy and also that there may be a small family of moderately related genes that encode type IIA Ca(2+)-ATPases in Arabidopsis. Evidence is also provided from RT-PCR that these genes are expressed in Arabidopsis. Hydropathy analysis predicts that the topology of the Arabidopsis type IIA proteins is similar to the animal SERCA proteins. Sequence and phylogenetic analyses suggest that the type IIA Ca(2+)-ATPases can be further divided into sub-groups.