title: Rice ascorbate peroxidase gene family encodes functionally diverse isoforms localized in different subcellular compartments.
abstract: Aerobic organisms evolved a complex antioxidant system, which protect the cells against oxidative damage caused by partially reduced oxygen intermediates, also known as reactive oxygen species. In plants, ascorbate peroxidases (EC, 1.11.1.11) catalyze the conversion of H(2)O(2) to H(2)O, using ascorbate as the specific electron donor in this enzymatic reaction. Previously, eight APx genes were identified in the rice (Oryza sativa L.) genome through in silico analysis: two cytosolic isoforms, two putative peroxisomal isoforms, and four putative chloroplastic ones. Using gene-specific probes, we confirmed the presence of the eight APx genes in the rice genome by Southern blot hybridization. Transcript accumulation analysis showed specific expression patterns for each member of the APx family according to developmental stage and in response to salt stress, revealing the complexity of the antioxidant system in plants. Finally, the subcellular localization of rice APx isoforms was determined using GFP-fusion proteins in BY-2 tobacco cells. In agreement with the initial prediction, OSAPX3 was localized in the peroxisomes. On the other hand, the OSAPX6-GFP fusion protein was found in mitochondria of the BY-2 cells, in contrast to the chloroplastic location predicted by sequence analysis. Our findings reveal the functional diversity of the rice APx genes and suggest complementation and coordination of the antioxidant defenses in different cellular compartments during development and abiotic stress.
authors.affiliation: Laboratório de Genética Molecular Vegetal, Departamento de Genética, Universidade Federal do Rio de Janeiro, 21944-970, Rio de Janeiro, Brasil.
authors.forename: Felipe Karam
authors.initials: FK
authors.lastname: Teixeira
authors.forename: Larissa
authors.initials: L
authors.lastname: Menezes-Benavente
authors.forename: Vinícius Costa
authors.initials: VC
authors.lastname: Galvão
authors.forename: Rogério
authors.initials: R
authors.lastname: Margis
authors.forename: Márcia
authors.initials: M
authors.lastname: Margis-Pinheiro
mesh_terms: D060387:Ascorbate Peroxidases; D015152:Blotting, Northern; D015139:Blotting, Southern; D035264:Flowers / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D007527:Isoenzymes / Q000378:metabolism; D012275:Oryza / Q000187:drug effects / Q000201:enzymology*; D010544:Peroxidases / Q000235:genetics / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism; D018547:Plant Stems / Q000378:metabolism; D030821:Plants, Genetically Modified; D021381:Protein Transport; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012492:Salts / Q000494:pharmacology; D036226:Seedlings / Q000378:metabolism; D013347:Subcellular Fractions / Q000201:enzymology; D014026:Nicotiana / Q000166:cytology
chemical_list: D007527:Isoenzymes; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D012492:Salts; D010544:Peroxidases; D060387:Ascorbate Peroxidases