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- Title
Homologs of Circadian Clock Proteins Impact the Metabolic Switch Between Light and Dark Growth in the Cyanobacterium Synechocystis sp. PCC 6803.
- Authors
Scheurer, Nina M.; Rajarathinam, Yogeswari; Timm, Stefan; Köbler, Christin; Kopka, Joachim; Hagemann, Martin; Wilde, Annegret
- Abstract
The putative circadian clock system of the facultative heterotrophic cyanobacterial strain Synechocystis sp. PCC 6803 comprises the following three Kai-based systems: a KaiABC-based potential oscillator that is linked to the SasA-RpaA two-component output pathway and two additional KaiBC systems without a cognate KaiA component. Mutants lacking the genes encoding the KaiAB1C1 components or the response regulator RpaA show reduced growth in light/dark cycles and do not show heterotrophic growth in the dark. In the present study, the effect of these mutations on central metabolism was analyzed by targeted and non-targeted metabolite profiling. The strongest metabolic changes were observed in the dark in Δ rpaA and, to a lesser extent, in the Δ kaiAB1C1 mutant. These observations included the overaccumulation of 2-phosphoglycolate, which correlated with the overaccumulation of the RbcL subunit in the mutants, and taken together, these data suggest enhanced RubisCO activity in the dark. The imbalanced carbon metabolism in the Δ rpaA mutant extended to the pyruvate family of amino acids, which showed increased accumulation in the dark. Hence, the deletion of the response regulator rpaA had a more pronounced effect on metabolism than the deletion of the kai genes. The larger impact of the rpaA mutation is in agreement with previous transcriptomic analyses and likely relates to a KaiAB1C1-independent function as a transcription factor. Collectively, our data demonstrate an important role of homologs of clock proteins in Synechocystis for balanced carbon and nitrogen metabolism during light-to-dark transitions.
- Subjects
SYNECHOCYSTIS; CARBON metabolism; CIRCADIAN rhythms; TRANSCRIPTION factors; PROTEINS; PYRUVATES
- Publication
Frontiers in Plant Science, 2021, Vol 12, p1
- ISSN
1664-462X
- Publication type
Article
- DOI
10.3389/fpls.2021.675227