Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 112, Issue 26, Pages 8082-8087Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1504228112
Keywords
photoreceptors; signal transduction; light sensing; second messenger; sessility
Categories
Funding
- Japan Society for the Promotion of Science Fellows and for Scientific Research
- Precursory Research for Embryonic Science and Technology, Japan Science and Technology Agency
- Core Research for Evolutional Science and Technology, Japan Science and Technology Agency
- Grants-in-Aid for Scientific Research [13J08415] Funding Source: KAKEN
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Cyanobacteriochromes (CBCRs) are cyanobacterial photoreceptors that have diverse spectral properties and domain compositions. Although large numbers of CBCR genes exist in cyanobacterial genomes, no studies have assessed whether multiple CBCRs work together. We recently showed that the diguanylate cyclase (DGC) activity of the CBCR SesA from Thermosynechococcus elongatus is activated by blue-light irradiation and that, when irradiated, SesA, via its product cyclic dimeric GMP (c-di-GMP), induces aggregation of Thermosynechococcus vulcanus cells at a temperature that is suboptimumfor single-cell viability. For this report, we first characterize the photobiochemical properties of two additional CBCRs, SesB and SesC. Blue/teal light-responsive SesB has only c-di-GMP phosphodiesterase (PDE) activity, which is up-regulated by teal light and GTP. Blue/green light-responsive SesC has DGC and PDE activities. Its DGC activity is enhanced by blue light, whereas its PDE activity is enhanced by green light. A Delta sesB mutant cannot suppress cell aggregation under teal-green light. A Delta sesC mutant shows a less sensitive cell-aggregation response to ambient light. Delta sesA/Delta sesB/Delta sesC shows partial cell aggregation, which is accompanied by the loss of color dependency, implying that a nonphotoresponsive DGC(s) producing c-di-GMP can also induce the aggregation. The results suggest that SesB enhances the light color dependency of cell aggregation by degrading c-di-GMP, is particularly effective under teal light, and, therefore, seems to counteract the induction of cell aggregation by SesA. In addition, SesC seems to improve signaling specificity as an auxiliary backup to SesA/SesB activities. The coordinated action of these three CBCRs highlights why so many different CBCRs exist.
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