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Ascorbate Metabolism and Nitrogen Fixation in Legumes

AutorMatamoros Galindo, Manuel Ángel ; Dalton, D. A.; Becana Ausejo, Manuel
Palabras claveAscorbate biosynthesis
Ascorbate peroxidase
Nitrogen fixation
Oxygen diffusion barrier
Fecha de publicación2017
CitaciónMatamoros MA, Dalton DA, Becana M. Ascorbate Metabolism and Nitrogen Fixation in Legumes. In: Hossain M, Munné-Bosch S, Burritt D, Diaz-Vivancos P, Fujita M, Lorence A (eds) Ascorbic Acid in Plant Growth, Development and Stress Tolerance. Springer, Cham (2017)
ResumenAscorbic acid (AsA) is a major antioxidant and redox buffer in plants that acts as a direct scavenger of reactive oxygen species (ROS), substrate of ascorbate peroxidase (APX), and cofactor of key enzymes involved in cell wall expansion and hormone biosynthesis. N2-fixing root nodules of legumes contain high levels of AsA (1–2 mM), APX (0.9% of the total soluble protein), and the other enzymes of the AsA-glutathione pathway. The AsA content and their associated enzyme activities are strongly correlated with N2 fixation, providing adequate protection of nodules against ROS generated by, among other processes, the oxidation of nitrogenase and leghemoglobin. These antioxidant defenses are concentrated in the infected zone and in the endodermis/nodule parenchyma, where they may be part of the O2 diffusion barrier that restricts entry of O2 into the nodule interior to avoid nitrogenase inactivation. AsA can enhance N2 fixation fourfold to fivefold when supplied by stem infusion to soybean plants or when added, along with APX, to an in vitro reconstitution system. GDP-d-mannose 3,5-epimerase (GME) and GDP-l-galactose phosphorylase (GGP) catalyze critical limiting steps in AsA biosynthesis. Consequently, studies are underway to produce transgenic N2-fixing plants that overexpress GME and GGP. Preliminary results have indicated that these plants have higher rates of N2 fixation but with a metabolic cost, resulting in slightly smaller plants. Additionally, since AsA oxidation and decline are early symptoms of nodule aging, a high AsA content might delay nodule senescence and extend the period of N2 fixation.
Descripción32 Pags.- 6 Figs.- 1 Tabl. The definitive version is available at: https://link.springer.com/book/10.1007/978-3-319-74057-7
Versión del editorhttps://doi.org/10.1007/978-3-319-74057-7_18
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