NO signaling functions in the biotic and abiotic stress responses

Abstract

Over the past two decades, it has been recognized that nitric oxide (NO) plays an important role in diverse mammalian physiological processes. NO regulates physiological processes by modulating the activity of proteins principally by nitrosylation, a process referring to the binding of NO to a transition metal centre or cysteine residues [1]. An important class of proteins that constitutes key targets of NO is that of the Ca2+ channels including plasma membranes as well intracellular Ca2+ channels. NO modulates these channels directly by nitrosylation, but also indirectly via the second messenger cyclic GMP (cGMP) and/or cyclic ADP ribose (cADPR). Therefore, NO emerges as a key messenger governing the overall control of Ca2+ homeostasis [2]. In the late 1990s, NO also became an increasingly popular target for investigation in plants. As in mammals, NO fulfils a broad spectrum of signaling functions in (patho)physiological processes in plants [3]. Here, we summarise studies published in recent years that provide novel insights into the signaling functions of NO produced by plant cells exposed to abiotic stresses and biotic stress (pathogen-derived elicitors). It focuses particularly on the cross-talk operating between NO and Ca2+.