title: Peroxisomal APX knockdown triggers antioxidant mechanisms favourable for coping with high photorespiratory H2 O2 induced by CAT deficiency in rice.
abstract: The physiological role of peroxisomal ascorbate peroxidases (pAPX) is unknown; therefore, we utilized pAPX4 knockdown rice and catalase (CAT) inhibition to assess its role in CAT compensation under high photorespiration. pAPX4 knockdown induced co-suppression in the expression of pAPX3. The rice mutants exhibited metabolic changes such as lower CAT and glycolate oxidase (GO) activities and reduced glyoxylate content; however, APX activity was not altered. CAT inhibition triggered different changes in the expression of CAT, APX and glutathione peroxidase (GPX) isoforms between non-transformed (NT) and silenced plants. These responses were associated with alterations in APX, GPX and GO activities, suggesting redox homeostasis differences. The glutathione oxidation-reduction states were modulated differently in mutants, and the ascorbate redox state was greatly affected in both genotypes. The pAPX suffered less oxidative stress and photosystem II (PSII) damage and displayed higher photosynthesis than the NT plants. The improved acclimation exhibited by the pAPX plants was indicated by lower H2 O2 accumulation, which was associated with lower GO activity and glyoxylate content. The suppression of both pAPXs and/or its downstream metabolic and molecular effects may trigger favourable antioxidant and compensatory mechanisms to cope with CAT deficiency. This physiological acclimation may involve signalling by peroxisomal H2 O2 , which minimized the photorespiration.
authors.affiliation: Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará, Fortaleza, CE, 60440-900, Brazil.
authors.forename: Rachel H V
authors.initials: RH
authors.lastname: Sousa
authors.forename: Fabricio E L
authors.initials: FE
authors.lastname: Carvalho
authors.forename: Carol W
authors.initials: CW
authors.lastname: Ribeiro
authors.forename: Gisele
authors.initials: G
authors.lastname: Passaia
authors.forename: Juliana R
authors.initials: JR
authors.lastname: Cunha
authors.forename: Yugo
authors.initials: Y
authors.lastname: Lima-Melo
authors.forename: Márcia
authors.initials: M
authors.lastname: Margis-Pinheiro
authors.forename: Joaquim A G
authors.initials: JA
authors.lastname: Silveira
mesh_terms: D000429:Alcohol Oxidoreductases / Q000235:genetics / Q000378:metabolism; D000975:Antioxidants / Q000378:metabolism*; D060387:Ascorbate Peroxidases / Q000235:genetics* / Q000378:metabolism; D002374:Catalase / Q000235:genetics / Q000378:metabolism; D019069:Cell Respiration; D018506:Gene Expression Regulation, Plant; D055785:Gene Knockdown Techniques; D005979:Glutathione Peroxidase / Q000235:genetics / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism*; D012275:Oryza / Q000201:enzymology / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D020675:Peroxisomes / Q000201:enzymology; D010788:Photosynthesis; D045332:Photosystem II Protein Complex / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified
chemical_list: D000975:Antioxidants; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D006861:Hydrogen Peroxide; D000429:Alcohol Oxidoreductases; C020821:glycollate oxidase; D060387:Ascorbate Peroxidases; D002374:Catalase; D005979:Glutathione Peroxidase
keywords: H2O2 homeostasis; Oryza sativa; ascorbate peroxidase; oxidative stress; photorespiration; signalling