Inactivation of thioredoxin reductases reveals a complex interplay between thioredoxin and glutathione pathways in Arabidopsis development.
NADPH-dependent thioredoxin reductases (NTRs) are key regulatory enzymes determining the redox state of the thioredoxin system. The Arabidopsis thaliana genome has two genes coding for NTRs (NTRA and NTRB), both of which encode mitochondrial and cytosolic isoforms. Surprisingly, plants of the ntra ntrb knockout mutant are viable and fertile, although with a wrinkled seed phenotype, slower plant growth, and pollen with reduced fitness. Thus, in contrast with mammals, our data demonstrate that neither cytosolic nor mitochondrial NTRs are essential in plants. Nevertheless, in the double mutant, the cytosolic thioredoxin h3 is only partially oxidized, suggesting an alternative mechanism for thioredoxin reduction. Plant growth in ntra ntrb plants is hypersensitive to buthionine sulfoximine (BSO), a specific inhibitor of glutathione biosynthesis, and thioredoxin h3 is totally oxidized under this treatment. Interestingly, this BSO-mediated growth arrest is fully reversible, suggesting that BSO induces a growth arrest signal but not a toxic accumulation of activated oxygen species. Moreover, crossing ntra ntrb with rootmeristemless1, a mutant blocked in root growth due to strongly reduced glutathione synthesis, led to complete inhibition of both shoot and root growth, indicating that either the NTR or the glutathione pathway is required for postembryonic activity in the apical meristem.
Reichheld
Jean-Philippe
JP
Laboratoire Génome et Développement des Plantes, Université de Perpignan, Unité Mixte de Recherche, Centre National de la Recherche Scientifique 5096, Perpignan, France. jpr@univ-perp.fr
Khafif
Mehdi
M
Riondet
Christophe
C
Droux
Michel
M
Bonnard
Géraldine
G
Meyer
Yves
Y
D000872:Anthocyanins / Q000378:metabolism; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D004171:Diploidy; D004789:Enzyme Activation; D005298:Fertility; D018506:Gene Expression Regulation, Plant; D005816:Genetic Complementation Test; D054477:Glutaredoxins; D005978:Glutathione / Q000378:metabolism*; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010088:Oxidoreductases / Q000378:metabolism; D010641:Phenotype; D018517:Plant Roots / Q000166:cytology / Q000254:growth & development; D011058:Pollen / Q000378:metabolism; D036226:Seedlings / Q000378:metabolism; D012639:Seeds / Q000378:metabolism; D013880:Thioredoxin-Disulfide Reductase / Q000235:genetics / Q000378:metabolism*; D013879:Thioredoxins / Q000378:metabolism*
D000872:Anthocyanins; D029681:Arabidopsis Proteins; D054477:Glutaredoxins; D013879:Thioredoxins; D010088:Oxidoreductases; C497521:NTRA protein, Arabidopsis; C497522:NTRB protein, Arabidopsis; D013880:Thioredoxin-Disulfide Reductase; D005978:Glutathione