Insight into calcium signalling in salt stress response

Abstract

• SOS pathway is a major pathway triggered by Ca 2+ under salt stress. • Silicon has a role in the improved functioning of the SOS pathway under salt stress. • Calcium signalling and ABA synthesis results in stomatal closure. • High cytosolic Ca 2+ results in upregulating ROS production. Owing to the sessile nature of plants, they are at the mercy of environmental conditions and are often subject to severe abiotic stresses. Amongst these abiotic stresses, high salinity stress is one of the most common and severe stresses affecting one-third of irrigated agricultural lands worldwide. Calcium ion is well known for its essential role as a mediator of signals and in regulating and specifying the cellular responses to abiotic stresses. To adapt to salt stress, one of the main strategies developed by plants is calcium signalling responses. The excess extracellular salt is detected by specific root receptors and resulted in immediate rise of cytosolic free Ca 2+ . Exhaustive research has been conducted to identify the genetic identities of Ca 2+ channels and signalling factors, developing novel findings on such tolerance mechanisms in plants. However, the complex interconnected system of the salinity stress response by Ca 2+ signalling in plants has not been adequately justified. Plants employ a combination of Ca 2+ integrated proteins, phytohormones, osmolytes, receptors and other signalling factors in response to salinity stress, making this a complex calcium response network. In this review, we summarise and discuss the role of calcium signalling in response to salinity stress. In contrast to other studies, we try to provide a holistic overview of both chemical and mechanical processes involved in salt stress response while expanding on gaps filled by recent research. Furthermore, based on existing knowledge, we evaluate the different types of mechanisms and pathways through which calcium signalling works.