Near-UV cyanobacteriochrome signaling system elicits negative phototaxis in the cyanobacterium Synechocystis sp. PCC 6803

Positive phototaxis systems have been well studied in bacteria; however, the photoreceptor(s) and their downstream signaling components that are responsible for negative phototaxis are poorly understood. Negative phototaxis sensory systems are important for cyanobacteria, oxygenic photosynthetic org...

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Published inProceedings of the National Academy of Sciences - PNAS Vol. 108; no. 26; pp. 10780 - 10785
Main Authors Song, Ji-Young, Cho, Hye Sun, Cho, Jung-Il, Jeon, Jong-Seong, Lagarias, J. Clark, Park, Youn-Il
Format Journal Article
LanguageEnglish
Published United States National Academy of Sciences 28.06.2011
National Acad Sciences
Subjects
autotrophs
Bacteria
Bacterial Proteins - metabolism
Biochemistry
Biological Sciences
Chromophores
Cyanobacteria
Electrophoretic Mobility Shift Assay
Gene expression
Genes
Genetic loci
Light
lighting
loci
Photic Stimulation
Photoreceptors
photosensitizing agents
Photosynthesis
Phototaxis
Promoter regions
reactive oxygen species
Regulator genes
RNA
Sensors
Signal Transduction
Synechocystis
Synechocystis - metabolism
Synechocystis - physiology
Ultraviolet radiation
Ultraviolet Rays
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Summary:Positive phototaxis systems have been well studied in bacteria; however, the photoreceptor(s) and their downstream signaling components that are responsible for negative phototaxis are poorly understood. Negative phototaxis sensory systems are important for cyanobacteria, oxygenic photosynthetic organisms that must contend with reactive oxygen species generated by an abundance of pigment photosensitizers. The unicellular cyanobacterium Synechocystis sp. PCC6803 exhibits type IV pilus-dependent negative phototaxis in response to unidirectional UV-A illumination. Using a reverse genetic approach, together with biochemical, molecular genetic, and RNA expression profiling analyses, we show that the cyanobacteriochrome locus (slr1212/uirS) of Synechocystis and two adjacent response regulator loci (slr1213/uirR and the PatA-type regulator slr1214/lsiR) encode a UV-A-activated signaling system that is required for negative phototaxis. We propose that UirS, which is membrane-associated via its ETR1 domain, functions as a UV-A photosensor directing expression of lsiR via release of bound UirR, which targets the lsiR promoter. Constitutive expression of LsiR induces negative phototaxis under conditions that normally promote positive phototaxis. Also induced by other stresses, LsiR thus integrates light inputs from multiple photosensors to determine the direction of movement.
Bibliography:http://dx.doi.org/10.1073/pnas.1104242108
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Edited by Alexander Namiot Glazer, University of California, Berkeley, CA, and approved May 23, 2011 (received for review March 16, 2011)
Author contributions: J.-Y.S., J.C.L., and Y.-I.P. designed research; J.-Y.S., H.S.C., J.-I.C., and J.-S.J. performed research; J.-Y.S., H.S.C., J.-I.C., J.-S.J., J.C.L., and Y.-I.P. analyzed data; and J.-Y.S., J.C.L., and Y.-I.P. wrote the paper.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.1104242108