NO and ROS crosstalk and acquisition of abiotic stress tolerance

Nitric oxide (NO) and H₂O₂, known as signaling molecules, particularly regulate various cellular processes under stress conditions. Abiotic stress, like other stresses, leads to the production of reactive oxygen and nitrogen species (ROS and RNS, respectively). The interaction or crosstalk between these two redox molecules is important for the regulation of cellular processes. Increasing evidence has suggested that NO transfers its bioactivity through posttranslational modifications, the major among them is S-nitrosation, the covalent attachment of an NO moiety to a cysteine thiol that can bring conformational changes in proteins and hence in their functions. S-nitrosation of the tripeptide glutathione (GSH) results in the formation of S-nitrosoglutathione (GSNO), which is a relatively stable reservoir of NO. The formation of GSNO, therefore, determines cellular redox status, crucial for normal metabolic activities, and is regulated by key enzyme GSNO reductase (GSNOR) in plants. Here, we overview the importance of H₂O₂ and NO as signaling molecules in plants and their roles in stress tolerance. We also discuss crosstalk between H₂O₂ and NO and its importance in abiotic stress tolerance, with examples of salt, cold, drought, metal, and heat tolerance. The accumulated data from the cited research has important implications for the improved productivity of many crop plants.