NO signalling functions in the biotic and abiotic stress responses.

In the last 1990s, NO became an increasingly popular target of investigation in plants. As in mammals, NO fulfils a broad spectrum of signalling functions in pathophysiological processes in plants. Here we summarize studies published in recent years that provide novel insights into the signalling functions of NO produced by plant cells exposed to abiotic stresses and biotic stress (pathogen-derived elicitors). Particularly, we report that NO emerges as a key messenger governing the overall control of Ca2+ homeostasis. Although the precise signalling functions of NO are poorly understood, its capacity to modulate Ca2+ homeostasis provides an extraordinary and remarkable effective way of conveying information.