Food security is in danger under the continuous growing threat of various stresses including climate change and global warming, which ultimately leads to a reduction in crop yields. Calcium plays a very important role in many signal transduction pathways including stress signalling. Different extracellular stimuli trigger increases in cytosolic calcium, which is detrimental to plants. To cope with such stresses, plants need to develop efficient efflux mechanisms to maintain ionic homeostasis. The Ca(2+)-ATPases are members of the P-type ATPase superfamily, which perform many fundamental processes in organisms by actively transporting ions across cellular membranes. In recent years, many studies have revealed that, as well as efflux mechanisms, Ca(2+)-ATPases also play critical roles in sensing calcium fluctuations and relaying downstream signals by activating definitive targets, thus modulating corresponding metabolic pathways. As calcium-activated calmodulin (CaM) is reported to play vital roles in stress tolerance, the presence of a unique CaM-binding site in type IIB Ca(2+)-ATPases indicates their potential role in biotic as well as abiotic stress tolerance. The key roles of Ca(2+)-ATPases in transport systems and stress signalling in cellular homeostasis are addressed in this review. A complete understanding of plant defence mechanisms under stress will allow bioengineering of improved crop plants, which will be crucial for food security currently observed worldwide in the context of global climate changes. Overall, this article covers classification, evolution, structural aspects of Ca(2+)-ATPases, and their emerging roles in plant stress signalling.
Keywords: Abiotic stress; Ca2+-ATPases; agriculture; biotic stress; calmodulin; efflux mechanism..