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Peroxisomal APX knockdown triggers antioxidant mechanisms favourable for coping with high photorespiratory H 2 O 2 induced by CAT deficiency in rice
Author(s) -
SOUSA RACHEL H. V.,
CARVALHO FABRICIO E. L.,
RIBEIRO CAROL W.,
PASSAIA GISELE,
CUNHA JULIANA R.,
LIMAMELO YUGO,
MARGISPINHEIRO MÁRCIA,
SILVEIRA JOAQUIM A. G.
Publication year - 2015
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/pce.12409
Subject(s) - apx , photorespiration , peroxisome , catalase , biochemistry , chemistry , peroxidase , glyoxylate cycle , oxidative stress , microbiology and biotechnology , biology , photosynthesis , metabolism , enzyme , gene
The physiological role of peroxisomal ascorbate peroxidases ( pAPX ) is unknown; therefore, we utilized pAPX 4 knockdown rice and catalase ( CAT ) inhibition to assess its role in CAT compensation under high photorespiration. pAPX 4 knockdown induced co‐suppression in the expression of pAPX 3. 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 H 2 O 2 accumulation, which was associated with lower GO activity and glyoxylate content. The suppression of both pAPX s 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 H 2 O 2 , which minimized the photorespiration.