Plant Ca2+-ATPases

Plant calcium pumps, similarly to animal Ca2+ Pumps, belong to the superfamily of P-type ATPascs comprising also the plasma membrane H+-ATPase of fungi and plants, Na+/K+ ATPase of aninials and H+/K+ ATPase of manimalian gastric mucosa. According to their sensitivity to calmodulin the plant Ca2+-ATPases have been divided into two subgroups: type IIA (homologues of animal SERCA) and type IIB (hornologucs of animal PMCA). Regardless of the similarities in a protein sequence, the plant Ca2+ pumps differ from those in animals in their cellular localization, structure and sensitivity to inhibitors. Genomic investigations revealed multiplicity of plant Ca2+-ATPascs; they are present not only in the plasma membranes, and ER but also in membranes of most of the cell compartments, Such as vacuole, plastids, nucleus or Golgi apparatus. Studies using yeast mutants made possible the functional and biochemical characterization of individual plant Ca2+-ATPases. Plant calcium pumps play an essential role in signal transduction pathways, they are responsible for the regulation of [Ca2+] in both cytoplasm and endomembrane compartments. These Ca2+-ATPascs appear to be involved in plant adaptation to stress conditions, like salinity, chilling or anoxia.