Poplar Peroxiredoxin Q. A Thioredoxin-Linked Chloroplast Antioxidant Functional in Pathogen Defense

• Published in: Plant physiology (Bethesda) 2004-03, Vol.134 (3), p.1027-1038
• Main Authors: Rouhier, Nicolas, Gelhaye, Eric, Gualberto, Jose M., Marie-Noelle Jordy, Elisabeth De Fay, Hirasawa, Masakazu, Duplessis, Sebastien, Lemaire, Stephane D., Pascal Frey, Martin, Francis, Manieri, Wanda, Knaff, David B., Jacquot, Jean-Pierre
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Antioxidants - metabolism; Base Sequence; Biochemical Processes and Macromolecular Structures; Biochemistry; Biological and medical sciences; Catalytic Domain - genetics; Chloroplast Thioredoxins; Chloroplasts; Chloroplasts - metabolism; Dimerization; Disulfides; DNA, Plant - genetics; Electron Transport; Enzymes; Fundamental and applied biological sciences. Psychology; Gene Expression; Generalities. Disease free stocks; Genes, Plant; Genetics; Infections; Leaves; Life Sciences; Macromolecular Substances; Metabolism; Molecular Sequence Data; Mutagenesis, Site-Directed; Oxidation-Reduction; Peroxidases - chemistry; Peroxidases - genetics; Peroxidases - metabolism; Peroxides; Peroxiredoxins; Phytopathology. Animal pests. Plant and forest protection; Plant Diseases - genetics; Plant Diseases - microbiology; Plant physiology and development; Plant Proteins - chemistry; Plant Proteins - genetics; Plant Proteins - metabolism; Plants; Plants genetics; Populus - genetics; Populus - metabolism; Populus - microbiology; Proteins; Recombinant Proteins - chemistry; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; Sequence Homology, Amino Acid; Substrate Specificity; Thioredoxin; Thioredoxins - metabolism
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.103.035865

Peroxiredoxins are ubiquitous thioredoxin- or glutaredoxin-dependent peroxidases, the function of which is to destroy peroxides. Peroxiredoxin Q, one of the four plant subtypes, is a homolog of the bacterial bacterioferritin comigratory proteins. We show here that the poplar (Populus tremula × Populus tremuloides) protein acts as a monomer with an intramolecular disulfide bridge between two conserved cysteines. A wide range of electron donors and substrates was tested. Unlike type II peroxiredoxin, peroxiredoxin Q cannot use the glutaredoxin or cyclophilin isoforms tested, but various cytosolic, chloroplastic, and mitochondrial thioredoxins are efficient electron donors with no marked specificities. The redox midpoint potential of the peroxiredoxin Q catalytic disulfide is -325 mV at pH 7.0, explaining why the wild-type protein is reduced by thioredoxin but not by glutaredoxin. Additional evidence that thioredoxin serves as a donor comes from the formation of heterodimers between peroxiredoxin Q and monocysteinic mutants of spinach (Spinacia oleracea) thioredoxin m. Peroxiredoxin Q can reduce various alkyl hydroperoxides, but with a better efficiency for cumene hydroperoxide than hydrogen peroxide and thertiary butyl hydroperoxide. The use of immunolocalization and of a green fluorescence protein fusion construct indicates that the transit sequence efficiently targets peroxiredoxin Q to the chloroplasts and especially to those of the guard cells. The expression of this protein and of type II peroxiredoxin is modified in response to an infection by two races of Melampsora larici-populina, the causative agent of the poplar rust. In the case of an hypersensitive response, the peroxiredoxin expression increased, whereas it decreased during a compatible interaction.