The involvement of mitochondrial electron transport chain components in nitric oxide metabolism in plants.
Jayawardhane J, Cochrane DW, Shah JK, Bykova NV, Vanlerberghe GC, Igamberdiev AU (2019) The involvement of mitochondrial electron transport chain components in nitric oxide metabolism in plants. The 14th International Conference on Reactive Oxygen and Nitrogen Species in Plants. Munich, Germany, July 10-12, 2019. Oral presentation
The components of the mitochondrial electron transport chain are involved not only in the reduction of oxygen as a terminal acceptor but also in the production of nitric oxide (NO) from nitrite which is facilitated during anaerobic stress. To investigate the role of the mitochondrial complex I and alternative oxidase (AOX) in NO metabolism, the wild type and transgenic tobacco (Nicotiana sp.) plants with different levels of expression of the complex I subunit NAD7 and AOX were subjected to nitrogen atmosphere and normal air. The NO emissions from plants were detected by the chemiluminescent NO analyzer, metabolite concentrations were measured by NMR analysis, and respiratory enzymes were assayed spectrophotometrically. A significant decrease in NO production was recorded under anoxia in the plants lacking complex I subunit NAD7 as compared to the wild type. The plants impaired in complex I were characterized by the elevated levels of phytoglobin even under normoxia, low level of aconitase and higher activities of the fermentation enzymes alcohol dehydrogenase and lactate dehydrogenase. The plants downregulating AOX exhibited low NO emissions and decreased levels of protein S-nitrosylation under hypoxia as compared to the plants overexpressing AOX, while under normoxia they showed higher S-nitrosylation levels. The pool size of amino acids and organic acids revealed a complex difference depending upon AOX amount under hypoxic and normoxic conditions, which was reflected in the levels of succinate, malate, glycine and γ-aminobutyric acid. AOX amount also strongly influenced the activity of aconitase under hypoxia. The level of superoxide, lipid peroxidation and total antioxidant reducing power increased in AOX-knockdown plants under normoxia and during re-oxygenation after hypoxia. It is concluded that both complex I and AOX have pervasive and oxygen concentration-dependent effects on NO production, protein S-nitrosylation, respiratory carbon and nitrogen flow, as well as on the metabolism of reactive oxygen species.