Knockout of major leaf ferredoxin reveals new redox-regulatory adaptations in Arabidopsis thaliana

Autor(en): Voss, Ingo
Koelmann, Meike
Wojtera, Joanna
Holtgrefe, Simone
Kitzmann, Camillo
Backhausen, Jan E.
Scheibe, Renate 
Stichwörter: CHLOROPLAST; LIGHT STRESS; NADP-MALATE DEHYDROGENASE; O-2 EVOLUTION; OVER-REDUCTION; OXIDATION-REDUCTION PROPERTIES; PHOTOSYNTHETIC ELECTRON-TRANSPORT; PHOTOSYSTEM-I; Plant Sciences; QUANTUM YIELD; THIOREDOXIN REDUCTASE
Erscheinungsdatum: 2008
Herausgeber: WILEY
Journal: PHYSIOLOGIA PLANTARUM
Volumen: 133
Ausgabe: 3
Startseite: 584
Seitenende: 598
Zusammenfassung: 
Ferredoxins are the major distributors for electrons to the various acceptor systems in plastids. In green tissues, ferredoxins are reduced by photosynthetic electron flow in the light, while in heterotrophic tissues, nicotinamide adenine dinucleotide (reduced) (NADPH) generated in the oxidative pentose-phosphate pathway (OPP) is the reductant. We have used a Ds-T-DNA insertion line of Arabidopsis thaliana for the gene encoding the major leaf ferredoxin (Fd2, At1g60950) to create a situation of high electron pressure in the thylakoids. Although these plants (Fd2-KO) possess only the minor fraction of leaf Fd1 (At1g10960), they grow photoautotrophically on soil, but with a lower growth rate and less chlorophyll. The more oxidized conditions in the stroma due to the formation of reactive oxygen species are causing a re-adjustment of the redox state in these plants that helps them to survive even under high light. Redox homeostasis is achieved by regulation at both, the post-translational and the transcriptional level. Over-reduction of the electron transport chain leads to increased transcription of the malate-valve enzyme NADP-malate dehydrogenase (MDH), and the oxidized stroma leads to an increased transcription of the OPP enzyme glucose-6-P dehydrogenase. In isolated spinach chloroplasts, oxidized conditions give rise to a decreased activation state of NADP-MDH and an activation of glucose-6-P dehydrogenase even in the light. In Fd2-KO plants, NADPH-requiring antioxidant systems are upregulated. These adjustments must be caused by plastid signals, and they prevent oxidative damage under rather severe conditions.
ISSN: 00319317
DOI: 10.1111/j.1399-3054.2008.01112.x

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