A specific form of thioredoxin h occurs in plant mitochondria and regulates the alternative oxidase.
The plant mitochondrial thioredoxin (Trx) system has been described as containing an NADPH-dependent Trx reductase and Trx o. In addition to the mitochondrial isoform, Trx o, plants are known to contain several chloroplastic Trx isoforms and the cytosolic Trx h isoforms. We report here the presence in plant mitochondria of a Trx isoform (PtTrxh2) belonging to the Trx h group. Western blot analyses with mitochondrial proteins isolated from both poplar and GFP fusion constructs indicate that PtTrxh2 is targeted to plant mitochondria. The recombinant protein, PtTrxh2, has been shown to be reduced efficiently by the mitochondrial Trx reductase AtNTRA. PtTrxh2 is also able to reduce alternative oxidase homodimers and to allow its activation by pyruvate. In contrast, neither PtTrxh2 nor AtTrxo1 exhibits activity with several poplar glutathione peroxidases and especially a putative mitochondrial isoform. Incubation of PtTrxh2 with glutathione disulfide led to the formation of glutathionylated Trx, identified by mass spectrometry. The formation of a glutathione adduct increases the redox potential of PtTrxh2 from -290 to -225 mV. In addition to Trx o, this study shows that Trx h could also be present in mitochondria. This previously unrecognized complexity is not unexpected, considering the multiple redox-regulated processes found in plant mitochondria.
Gelhaye
Eric
E
Unité Mixte de Recherche, Institut National de la Recherche Agronomique 1136, Interactions Arbres/Micro-organismes, Université Henri Poincaré, Faculté des Sciences et Techniques, BP 239 54506 Vandoeuvre Cedex, France. gelhaye@lcb.uhp-nancy.fr
Rouhier
Nicolas
N
Gérard
Joelle
J
Jolivet
Yves
Y
Gualberto
José
J
Navrot
Nicolas
N
Ohlsson
Per-Ingvard
PI
Wingsle
Gunnar
G
Hirasawa
Masakazu
M
Knaff
David B
DB
Wang
Hongmei
H
Dizengremel
Pierre
P
Meyer
Yves
Y
Jacquot
Jean-Pierre
JP
D001483:Base Sequence; D004274:DNA, Recombinant / Q000235:genetics; D005979:Glutathione Peroxidase / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism*; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D010944:Plants / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D032107:Populus / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D054480:Thioredoxin h; D000099188:Alternative Oxidase
D004274:DNA, Recombinant; D005979:Glutathione Peroxidase; D024101:Mitochondrial Proteins; D010088:Oxidoreductases; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D054480:Thioredoxin h; D000099188:Alternative Oxidase