Nitric oxide metabolism and its interaction with reactive oxygen species during the adaptation of plants to abiotic stress

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Nitric oxide (NO) is a potent bioactive molecule that plays a role in the metabolic and signaling functions of plants, providing flexible metabolism, regulation of key gene expression and enzyme activity involved in plant adaptations to stress. Plants have evolved to use mechanisms of energy conservation and transformation, including the use of pyrophosphate as a substitute for ATP in stress conditions and the use of electron transport components in redox reactions that contain NO. My long-term research goal is to establish the physiological role of NO turnover and phytoglobin function in the bioenergetics of stressed plant cells via the maintenance of redox and energy level and regulation of programmed cell death, autophagy, seed germination, and morphogenetic events. Specific objectives include: 1) exploring the phytoglobin-NO cycle, including a) differences between closed and opened modes, b) rates of cycle turnover and their dependence on oxygen availability using stable isotopes of oxygen and nitrogen, c) links between NO production, scavenging and energy status via the maintenance and formation of ATP and pyrophosphate, and d) links between NO metabolism and regulation of plant secondary metabolism/phenolics synthesis; 2) investigating the role of the mitochondrial electron transport in NO production and scavenging and associations with oxygen concentration, including the participation of alternative oxidase and cytochrome c oxidase in NO turnover; 3) studying the mechanisms of gene expression and epigenetic regulation leading to the induction of phytoglobins and the maintenance of NO turnover in plants under hypoxic stress; 4) exploring crosstalk between reactive oxygen and nitrogen species during seed germination, focusing on a) the formation of peroxynitrite from NO and superoxide, b) the dependence on changing oxygen concentrations, and c) the involvement of S-nitrosylation of proteins. Transgenic barley (Hordeum vulgare) and Arabidopsis (Arabidopsis thaliana) plants will be used to study the role of phytoglobins in maintaining low NO levels under stress. The switch between closed and open modes in operation of the cycle involving phytoglobin, NO and nitrate/nitrite will be studied using proteomic and metabolomic approaches. Crosstalk between NO, S-nitrosoglutathione and reactive oxygen species will be studied in relation to expression of phytoglobin and the components of the mitochondrial electron transport chain. The metabolism of NO and reactive nitrogen and oxygen species is a new potential target for improved resistance of agricultural plants to abiotic/biotic stress. The development of strategies for mitigating the consequences of limited oxygen availability in plants and in the regulation of seed germination will improve the resistance of agricultural plants to stress and maintain agricultural crop yields, particularly in the face of increasingly unpredictable weather events and climate change.