A Trio Of Photoreceptors Orchestrate Cell Aggregation

Having multiple photoreceptors allows cyanobacteria to coordinate complex processes such as cell aggregation, scientists say.

AsianScientist (Sep. 15, 2015) – In a study published in the Proceedings of the National Academy of Science, researchers from the University of Tokyo have shown how a trio of cyanobacteria photoreceptors coordinate light-dependent cell aggregation.

Cyanobacteria are a type of microalgae that perform photosynthesis like terrestrial plants and have sophisticated light-sensing systems to adapt to ambient light conditions. Cyanobacteriochrome, one group of the cyanobacterial photoreceptors, can sense different colors of light covering the entire visible spectrum. The cyanobacteriochrome found in cyanobacteria exists in far greater numbers than other photoreceptors, but why this should be so was unknown.

The research group of Professor Masahiko Ikeuchi at the University of Tokyo Graduate School of Arts and Sciences decoded the genomes of three cyanobacteriochromes (SesA, SesB and SesC) in cyanobacteria that aggregate in response to blue/green light.

They recently showed that SesA is activated by blue light irradiation, and activates a downstream signaling pathway, diguanylate cyclase. This activation aggregates thermophilic cyanobacterium. SesB is activated by blue/teal light and activates the phosphodiesterase pathway. Lastly, SesC is activated by blue/green light and activates both diguanylate cyclase and phosphodiesterase pathway.

They speculated that these different but overlapping color sensing functions of cynaobacterium may work in concert to detect color, and act as back up for another.

The application of the signal transduction system discovered in this research may be useful for regulation of photosynthetic production and recovery of the produced biomass, for example by designing a photoreceptor that induces cell aggregation in response to a particular color of light, or artificially switches photosynthetic biomass production on or off.

The article can be found at: Enomoto et al. (2015) Three Cyanobacteriochromes Work Together to Form a Light Color-Sensitive Input System for c-di-GMP Signaling of Cell Aggregation.

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Source: The University of Tokyo.
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