Photosynthetischer Elektronenfluss: Regulationsmechanismen und die zentrale Rolle der Ferredoxine

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Titel: Photosynthetischer Elektronenfluss: Regulationsmechanismen und die zentrale Rolle der Ferredoxine
Autor(en): Voß, Ingo
Erstgutachter: Prof. Dr. Renate Scheibe
Zweitgutachter: Prof. Dr. Richard Wagner
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. In this work Ds-T-DNA-insertion line of Arabidopsis thaliana for the coding region of the major leaf ferredoxin (Fd2, At1g60950) is used to create a situation of high electron pressure in the thylakoids. The highly reduced photosynthetic electron transport chain causes an extreme form of acclimation to high light, while the oxidized stroma leads to a re-adjustment of the chloroplast metabolism helping the plants to survive under these light-stress conditions. Redox homeostasis is achieved by regulation at both, the post-transcriptional and the transcriptional level. Alterations in gene expression due to acclimation via retrograte signalling are caused by a signal originating from the reduced photosynthetic electron flow. Using additionally Ds-T-DNA-insertion lines of A. thaliana for the coding region of Fd1 and transgenic approaches for gene silencing of Fd1, different functions of the two photosynthetic isoforms in A. thaliana are observed. Thereby Fd1 plays a significant role in Fd-dependent cyclic electron flow, and Fd2 predominantly drives the linear elelctron flow to generate NADPH. However, these specific functions are partly redundant. Using these transgenic lines of A. thaliana the essential function of ferredoxin-dependent cyclic electron flow in C3-plants became clear. In addition to the known ferredoxin isoforms in A. thaliana, the genome contains sequences coding for novel, unstudied ferredoxin-like proteins (FdC1 and FdC2) with extended C-termini, for which there are homologues in other photosynthetic organisms. In the Ds-T-DNA-insertion line of A. thaliana for the coding region of Fd2, the transcript level of FdC1 is increased. This implies an important role for FdC1 under conditions of high-electron pressure in the photosynthetic electron transport chain.
Schlagworte: Ferredoxin; Photosynthese; Photosynthetischer Elektronenfluss
Erscheinungsdatum: 27-Jan-2010
Enthalten in den Sammlungen:FB05 - E-Dissertationen

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