Photorespiratory 2-phosphoglycolate metabolism and photoreduction of O sub(2) cooperate in high-light acclimation of Synechocystis sp. strain PCC 6803

• Published in: Planta 2009-09, Vol.230 (4), p.625-637
• Main Authors: Hackenberg, Claudia, Engelhardt, Annerose, Matthijs, Hans CP, Wittink, Floyd, Bauwe, Hermann, Kaplan, Aaron, Hagemann, Martin
• Format: Article
• Language: English
• Subjects: Cyanobacteria; Synechocystis
• ISSN: 0032-0935; 1432-2048
• DOI: 10.1007/s00425-009-0972-9

In cyanobacteria, photorespiratory 2-phosphoglycolate (2PG) metabolism is mediated by three different routes, including one route involving the glycine decarboxylase complex (Gcv). It has been suggested that, in addition to conversion of 2PG into non-toxic intermediates, this pathway is important for acclimation to high-light. The photoreduction of O sub(2) (Mehler reaction), which is mediated by two flavoproteins Flv1 and Flv3 in cyanobacteria, dissipates excess reductants under high-light by the four electron-reduction of oxygen to water. Single and double mutants defective in these processes were constructed to investigate the relation between photorespiratory 2PG-metabolism and the photoreduction of O sub(2) in the cyanobacterium Synechocystis sp. PCC 6803. The single mutants Iflv1, Iflv3, and IgcvT, as well as the double mutant Iflv1/IgcvT, were completely segregated but not the double mutant Iflv3/IgcvT, suggesting that the T-protein subunit of the Gcv (GcvT) and Flv3 proteins cooperate in an essential process. This assumption is supported by the following results: (1) The mutant Iflv3/IgcvT showed a considerable longer lag phase and sometimes bleached after shifts from slow (low light, air CO sub(2)) to rapid (standard light, 5% CO sub(2)) growing conditions. (2) Photoinhibition experiments indicated a decreased ability of the mutant Iflv3/IgcvT to cope with high-light. (3) Fluorescence measurements showed that the photosynthetic electron chain is reduced in this mutant. Our data suggest that the photorespiratory 2PG-metabolism and the photoreduction of O sub(2), particularly that catalyzed by Flv3, cooperate during acclimation to high-light stress in cyanobacteria. Electronic supplementary material The online version of this article (doi:10.1007/s00425-009-0972-9) contains supplementary material, which is available to authorized users.