Calcium Signaling and Its Significance in Alleviating Salt Stress in Plants

Abstract

Environmental stresses such as salinity, temperature, drought and heavy metals negatively impact the agricultural productivity. Of these, salinity stands as a major problem mainly in the developing countries. Calcium is an essential nutrient that regulates the plant growth and development and it has evolved as a ubiquitous secondary messenger in mediating complex responses towards various developmental and environmental cues. Thus, understanding the calcium signaling and consequent calcium-dependent events is essential to improve plant productivity under extreme environment. The first step in calcium signaling is the induction of [Ca2+]cyt-transient/signatures which is defined as the repetitive oscillations or spiking of [Ca2+]cyt level. This in turn activates a set of calcium binding proteins including Ca2+ sensors/decoders, protein kinases and transcription factors. The interplay between Ca2+ signatures and these proteins together contributes towards the stimulus specificity. Various efforts have been made to manipulate calcium signaling events either by exogenous calcium supplementation or by genetic modification of calcium signaling related genes in many plant species and considerable progress has been made in managing the plant responses toward salt stress. Additionally, these studies also help in understanding the effect of salt stress on the process of calcium signaling. The present review deals with the basic steps of calcium signaling process and its possible modulations that can lead to the enhanced salt tolerance in plants.