Multifaceted roles of nitric oxide in plants

Nitric oxide (NO) is a reactive free radical gaseous molecule with a broad spectrum of regulatory functions in plant growth and development, and in response to abiotic and biotic (pathogenic and symbiotic interactions) factors. It is known to act either as a signaling molecule (mainly via redox-dependent post-translational modifications), a metabolic intermediate, or a toxic oxidative by-product. The reviews and research papers in this special issue summarize recent advances in our knowledge of plant NO production and degradation pathways, examine NO signaling mechanisms, and highlight its crosstalk with reactive oxygen species, hydrogen sulfide, and hormone-signaling processes for regulation of plant growth and responses to external stimuli.