Roles of Nitric Oxide in Conferring Multiple Abiotic Stress Tolerance in Plants and Crosstalk with Other Plant Growth Regulators

Nitric oxide (NO) is a free-radical gasotransmitter signaling molecule associated with a varied spectrum of signal transduction pathways linked to inducing cross-adaptation against abiotic stresses. It has crucial roles from seed germination to plant maturity, depending upon its cellular concentration. The functional cross-talk of NO among different stress signaling cascades leads to alteration in the expression of developmental genes that regulate biosynthesis and function of plant growth regulators (PGRs). NO-PGRs and secondary signaling compounds cross-talk trigger reprogramming of stress-responsive gene expressions, transcriptional gene modulations, redox regulating machinery, oxidative metabolisms, and multiple regulatory pathways under plant abiotic stress. Recent findings suggest NO as critical components of numerous plant signaling network that interplays with auxin, gibberellins (GA), abscisic acid (ABA), ethylene (ET), jasmonic acid (JA), brassinosteroids (BRs), H2O2, melatonin, hydrogen sulfide (H2S), salicylic acid (SA), and other PGRs to modulate growth and development under multiple stresses. Considering the importance of NO signaling crosstalk under stress adaptation, in this review, we point out the biosynthesis and metabolism of NO and its crosstalk with numerous other signaling compounds. Further, recent cellular and molecular advances in NO signaling cross-talk under abiotic stress adaptations also have been discussed.