Thioredoxin f1 and NADPH-Dependent Thioredoxin Reductase C Have Overlapping Functions in Regulating Photosynthetic Metabolism and Plant Growth in Response to Varying Light Conditions. Issue 3 (3rd September 2015)

• Record Type: Journal Article
• Authors: Thormählen, Ina; Meitzel, Tobias; Groysman, Julia; Öchsner, Alexandra Bianca; von Roepenack-Lahaye, Edda; Naranjo, Belén; Cejudo, Francisco J.; Geigenberger, Peter
• Is Part Of: Plant physiology. Volume 169:Issue 3(2015)
• Page Start: 1766
• Page End: 1786
• Publication Date: 2015-09-03
• Subjects: Plant physiology -- Periodicals; Botany -- Periodicals; Periodicals; Electronic journals; 571.2
• DOI: 10.1104/pp.15.01122
• Languages: English
• ISSNs: 0032-0889

Abstract

Abstract : A previously unrecognized interaction between light and NADPH-dependent thiol-redox systems affects photosynthetic metabolism and growth in response to varying light conditions. Abstract: Two different thiol redox systems exist in plant chloroplasts, the ferredoxin-thioredoxin (Trx ) system, which depends on ferredoxin reduced by the photosynthetic electron transport chain and, thus, on light, and the NADPH-dependent Trx reductase C (NTRC) system, which relies on NADPH and thus may be linked to sugar metabolism in the dark. Previous studies suggested, therefore, that the two different systems may have different functions in plants. We now report that there is a previously unrecognized functional redundancy of Trx f 1 and NTRC in regulating photosynthetic metabolism and growth. In Arabidopsis ( Arabidopsis thaliana ) mutants, combined, but not single, deficiencies of Trx f 1 and NTRC led to severe growth inhibition and perturbed light acclimation, accompanied by strong impairments of Calvin-Benson cycle activity and starch accumulation. Light activation of key enzymes of these pathways, fructose-1, 6-bisphosphatase and ADP-glucose pyrophosphorylase, was almost completely abolished. The subsequent increase in NADPH-NADP + and ATP-ADP ratios led to increased nitrogen assimilation, NADP-malate dehydrogenase activation, and light vulnerability of photosystem I core proteins. In an additional approach, reporter studies show that Trx f 1 and NTRC proteins are both colocalized in the same chloroplast substructure. Results provide genetic evidence that light- and NADPH-dependent thiol redox systems interact at the level of Trx f 1 and NTRC to coordinately participate in the regulation of the Calvin-Benson cycle, starch metabolism, and growth in response to varying light conditions.