Functional analysis of the pathways for 2-Cys peroxiredoxin reduction in Arabidopsis thaliana chloroplasts.
Photosynthesis is a process that inevitably produces reactive oxygen species, such as hydrogen peroxide, which is reduced by chloroplast-localized detoxification mechanisms one of which involves 2-Cys peroxiredoxins (2-Cys Prxs). Arabidopsis chloroplasts contain two very similar 2-Cys Prxs (denoted A and B). These enzymes are reduced by two pathways: NADPH thioredoxin reductase C (NTRC), which uses NADPH as source of reducing power; and plastidial thioredoxins (Trxs) coupled to photosynthetically reduced ferredoxin of which Trx chi is the most efficient reductant in vitro. With the aim of establishing the functional relationship between NTRC, Trx x, and 2-Cys Prxs in vivo, an Arabidopsis Trx chi knock-out mutant has been identified and a double mutant (denoted Delta 2cp) with <5% of 2-Cys Prx content has been generated. The phenotypes of the three mutants, ntrc, trxx, and Delta 2cp, were compared under standard growth conditions and in response to continuous light or prolonged darkness and oxidative stress. Though all mutants showed altered redox homeostasis, no difference was observed in response to oxidative stress treatment. Moreover, the redox status of the 2-Cys Prx was imbalanced in the ntrc mutant but not in the trxx mutant. These results show that NTRC is the most relevant pathway for chloroplast 2-Cys Prx reduction in vivo, but the antioxidant function of this system is not essential. The deficiency of NTRC caused a more severe phenotype than the deficiency of Trx chi or 2-Cys Prxs as determined by growth, pigment content, CO(2) fixation, and F(v)/F(m), indicating additional functions of NTRC.
Pulido
Pablo
P
Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla and CSIC, Avda Américo Vespucio 49, 41092-Sevilla, Spain.
Spínola
María Cristina
MC
Kirchsteiger
Kerstin
K
Guinea
Manuel
M
Pascual
María Belén
MB
Sahrawy
Mariam
M
Sandalio
Luisa María
LM
Dietz
Karl-Josef
KJ
González
Maricruz
M
Cejudo
Francisco Javier
FJ
D000975:Antioxidants / Q000378:metabolism; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000378:metabolism*; D002736:Chloroplasts / Q000201:enzymology* / Q000378:metabolism; D003545:Cysteine / Q000378:metabolism; D003624:Darkness; D006861:Hydrogen Peroxide / Q000378:metabolism; D008027:Light; D009249:NADP / Q000378:metabolism; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000502:physiology; D054464:Peroxiredoxins / Q000378:metabolism*; D010788:Photosynthesis; D013880:Thioredoxin-Disulfide Reductase / Q000378:metabolism; D013879:Thioredoxins / Q000378:metabolism
D000975:Antioxidants; D029681:Arabidopsis Proteins; D013879:Thioredoxins; D009249:NADP; D006861:Hydrogen Peroxide; D054464:Peroxiredoxins; D013880:Thioredoxin-Disulfide Reductase; D003545:Cysteine