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iScience. 2020 Mar 27;23(3):100936. doi: 10.1016/j.isci.2020.100936. Epub 2020 Feb 25.

Blue-/Green-Light-Responsive Cyanobacteriochromes Are Cell Shade Sensors in Red-Light Replete Niches.

Author information

1
Department of Life Sciences (Biology), Graduate School of Arts and Sciences, The University of Tokyo, Komaba 3-8-1, Meguro, Tokyo 153-8902, Japan. Electronic address: gen.enomoto@biologie.uni-freiburg.de.
2
Department of Life Sciences (Biology), Graduate School of Arts and Sciences, The University of Tokyo, Komaba 3-8-1, Meguro, Tokyo 153-8902, Japan.

Abstract

Cyanobacteriochrome (CBCRs) photoreceptors show various photochemical properties, but their ecophysiological functions remain elusive. Here, we report that the blue/green CBCRs SesA/B/C can serve as physiological sensors of cell density. Because cyanobacterial cells show lower transmittance of blue light than green light, higher cell density gives more green-light-enriched irradiance to cells. The cell-density-dependent suppression of cell aggregation under blue-/green-mixed light and white light conditions support this idea. Such a sensing mechanism may provide information about the cell position in cyanobacterial mats in hot springs, the natural habitat of Thermosynechococcus. This cell-position-dependent SesA/B/C-mediated regulation of cellular sessility (aggregation) might be ecophysiologically essential for the reorganization and growth of phototrophic mats. We also report that the green-light-induced dispersion of cell aggregates requires red-light-driven photosynthesis. Blue/green CBCRs might work as shade detectors in a different niche than red/far-red phytochromes, which may be why CBCRs have evolved in cyanobacteria.

KEYWORDS:

Biological Sciences; Microbiology; Sensor

Conflict of interest statement

Declaration of Interests The authors declare no competing interests.

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