Nitric oxide under abiotic stress conditions

Abstract Plants usually face adverse environmental conditions that can compromise their viability and therefore have a high influence on crop productivity and a great economic impact. It is predicted that food shortage will become a real concern in the forthcoming decades. For this reason, understanding how plants survive under these environmental changes will be of an invaluable help for breeding programs to develop crop with an improved tolerance to abiotic stresses. The adverse environmental changes are characterized by a fast burst of signaling molecules, which induces a complex response mechanism in plants such as reactive oxygen- and nitrogen-derived species (ROS) (RNS), highlighting hydrogen peroxide (H2O2) and nitric oxide (NO), respectively. NO is a fundamental molecule involved in the regulation of key processes during the whole life cycle of plants, including plant response to stress. Most studies available have used pharmacological approaches showing that exogenous NO positively regulates plant development under abiotic stresses via control of ROS and antioxidant systems. However, endogenous NO source(s) is(are) still under debate in plants, and therefore efforts should be focused on the identification of the specific NO source under different abiotic stresses. Moreover, NO mainly transmits its bioactivity by posttranslational modifications of proteins, chief among them being S-nitrosylation and tyrosine nitration. A high number of proteins have been identified as NO targets during plant response to stress, but a deeper characterization of these modifications at molecular level such as the impact on plant structure and/or function are still required. In this chapter, we will summarize the most recent information on NO function during plant response to several abiotic stresses.