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Biochim Biophys Acta Gen Subj. 2020 Jan;1864(1):129462. doi: 10.1016/j.bbagen.2019.129462. Epub 2019 Oct 26.

Evidence for convergent sensing of multiple abiotic stresses in cyanobacteria.

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Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada.
Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, Dresden 01307, Germany. Electronic address:
Department of Cell and Systems Biology, University of Toronto, Mississauga, ON L5L 1C6, Canada.
Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada. Electronic address:



Bacteria routinely utilize two-component signal transduction pathways to sense and alter gene expression in response to environmental cues. While cyanobacteria express numerous two-component systems, these pathways do not regulate all of the genes within many of the identified abiotic stress-induced regulons.


Electron transport inhibitors combined with western analysis and measurement of chlorophyll a fluorescent yield, using pulse amplitude modulation fluorometry, were used to detect the effect of a diverse range of abiotic stresses on the redox status of the photosynthetic electron transport chain and the accumulation and degradation of the Synechocystis sp. PCC 6803 DEAD box RNA helicase, CrhR.


Alterations in CrhR abundance were tightly correlated with the redox poise of the electron transport chain between QA and cytochrome b6f, with reduction favoring CrhR accumulation.


The results provide evidence for an alternative, convergent sensing mechanism mediated through the redox poise of QB/PQH2 that senses multiple, divergent forms of abiotic stress and regulates accumulation of CrhR. The RNA helicase activity of CrhR could then function as a post-translational effector to regulate downstream gene expression.


The potential for a related system in Staphylococcus aureus and higher plant chloroplasts suggest convergent sensing mechanisms may be evolutionarily conserved and occur more widely than anticipated.


Convergent sensing abiotic stress; CrhR DEAD box RNA helicase; Photosynthetic electron transport; Pulse amplitude modulation fluorometry (PAM); Redox poise plastoquinone pool; Synechocystis sp. PCC 6803

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