title: Rice NTRC is a high-efficiency redox system for chloroplast protection against oxidative damage.
abstract: One of the mechanisms plants have developed for chloroplast protection against oxidative damage involves a 2-Cys peroxiredoxin, which has been proposed to be reduced by ferredoxin and plastid thioredoxins, Trx x and CDSP32, the FTR/Trx pathway. We show that rice (Oryza sativa) chloroplast NADPH THIOREDOXIN REDUCTASE (NTRC), with a thioredoxin domain, uses NADPH to reduce the chloroplast 2-Cys peroxiredoxin BAS1, which then reduces hydrogen peroxide. The presence of both NTR and Trx-like domains in a single polypeptide is absolutely required for the high catalytic efficiency of NTRC. An Arabidopsis thaliana knockout mutant for NTRC shows irregular mesophyll cell shape, abnormal chloroplast structure, and unbalanced BAS1 redox state, resulting in impaired photosynthesis rate under low light. Constitutive expression of wild-type NTRC in mutant transgenic lines rescued this phenotype. Moreover, prolonged darkness followed by light/dark incubation produced an increase in hydrogen peroxide and lipid peroxidation in leaves and accelerated senescence of NTRC-deficient plants. We propose that NTRC constitutes an alternative system for chloroplast protection against oxidative damage, using NADPH as the source of reducing power. Since no light-driven reduced ferredoxin is produced at night, the NTRC-BAS1 pathway may be a key detoxification system during darkness, with NADPH produced by the oxidative pentose phosphate pathway as the source of reducing power.
authors.affiliation: Instituto de Bioquímica Vegetal y Fotosíntesis, Centro de Investigaciones Científicas Isla de la Cartuja, 41092 Seville, Spain.
authors.forename: Juan Manuel
authors.initials: JM
authors.lastname: Pérez-Ruiz
authors.forename: María Cristina
authors.initials: MC
authors.lastname: Spínola
authors.forename: Kerstin
authors.initials: K
authors.lastname: Kirchsteiger
authors.forename: Javier
authors.initials: J
authors.lastname: Moreno
authors.forename: Mariam
authors.initials: M
authors.lastname: Sahrawy
authors.forename: Francisco Javier
authors.initials: FJ
authors.lastname: Cejudo
mesh_terms: D017360:Arabidopsis / Q000033:anatomy & histology / Q000201:enzymology / Q000235:genetics; D029681:Arabidopsis Proteins; D002736:Chloroplasts / Q000378:metabolism*; D003001:Cloning, Molecular; D003624:Darkness; D004926:Escherichia coli / Q000235:genetics; D008954:Models, Biological; D008969:Molecular Sequence Data; D012275:Oryza / Q000201:enzymology* / Q000235:genetics; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010544:Peroxidases / Q000235:genetics / Q000378:metabolism; D054464:Peroxiredoxins; D010788:Photosynthesis / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics / Q000502:physiology*; D013880:Thioredoxin-Disulfide Reductase / Q000235:genetics / Q000502:physiology*; D013879:Thioredoxins / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D010940:Plant Proteins; D013879:Thioredoxins; D010544:Peroxidases; C108214:BAS1 protein, Arabidopsis; D054464:Peroxiredoxins; D013880:Thioredoxin-Disulfide Reductase