Raina, MeenakshiKisku, Arun VincentJoon, ShikhaKumar, SanjeevKumar, Deepak2025-01-302025-01-302021978-012821792-4https://dl.bhu.ac.in/ir/handle/123456789/25848Plants exhibit diverse mechanisms to combat an array of environmental stress factors. These comprise intricate but well-regulated signaling pathways. Cytosolic free calcium (Ca+2) is an important secondary messenger of abiotic stress in plants. In general, it senses the stress stimuli and activates downstream protein targets. Calmodulin (CaMs) and calmodulin-like proteins (CMLs) are the key players in the Ca+2-mediated abiotic stress signaling cascade in the plants. They sense the altered Ca+2 concentrations in the cell cytosol and are actively involved in signal perception and transmission. These, in turn, interact with a spectrum of effector regulatory proteins forming a relay network of a signal transduction pathway. Consequently, the expression of stress-related genes is either upregulated or downregulated depending on the stressor and the plant organelles affected. Examples include cold and heat stress genes and those involved in reactive oxygen species homeostasis pathway. Finally, an appropriate response is generated ensuring reestablishment of cellular homeostasis in different plant organelles. This chapter discusses the indispensability of Ca+2 and Ca+2-binding proteins, that is, CaMs and CMLs, in abiotic stress signaling in plants and the pathways involved. � 2021 Elsevier Inc. All rights reserved.Abiotic stressCalcium (Ca<sup>+2</sup>)Calmodulin (CaMs)Calmodulin-like proteins (CMLs)HomeostasisSignaling pathwayCalmodulin and calmodulin-like Ca2+ binding proteins as molecular players of abiotic stress response in plantsBook chapterhttps://doi.org/10.1016/B978-0-12-821792-4.00001-1