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bioRxiv · 10.1101/2021.07.26.453758

Uncoupling of the Diurnal Growth Program by Artificial Genome Relaxation in Synechocystis sp. PCC 6803

Behle, A.·Dietsch, M.·Goldschmidt, L.·Murugathas, W.·Brandt, D.·Busche, T.·Kalinowski, J.·Ebenhoeh, O.·Axmann, I. M.·Machne, R.
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Abstract

In cyanobacteria DNA supercoiling varies over the diurnal light/dark cycle and is integrated with temporal programs of transcription and replication. We manipulated DNA supercoiling in Synechocystis sp. PCC 6803 by CRISPRi-based knock-down of gyrase subunits and overexpression of topoisomerase I (TopoI), and characterized the phenotypes. Cell division was blocked, most likely due to inhibition of genomic but not plasmid DNA replication. Cell growth continued to 4-5x of the wildtype cell volume, and metabolic flux was redirected towards glycogen in the TopoI overexpression strain. TopoI induction initially lead to down-regulation of GC-rich and up-regulation of AT-rich genes. The response quickly bifurcated and four diurnal co-expression cohorts (dawn, noon, dusk and night) all responded differently, in part with a circadian ({approx} 24 h) pattern. A GC-rich region - 50 bp of transcription start sites is differentially enriched in these four cohorts. We suggest a model where energy- and gyrase-gated transcription of growth genes at the dark/light transition (dawn) generates DNA supercoiling which then facilitates DNA replication and initiates the diurnal transcriptome program.

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Behle, A., Dietsch, M., Goldschmidt, L., Murugathas, W., Brandt, D., Busche, T., Kalinowski, J., Ebenhoeh, O., Axmann, I. M., Machne, R.. 2021-07-27. Uncoupling of the Diurnal Growth Program by Artificial Genome Relaxation in Synechocystis sp. PCC 6803. https://doi.org/10.1101/2021.07.26.453758

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