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

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Title
Near-UV cyanobacteriochrome signaling system elicits negative phototaxis in the cyanobacterium Synechocystis sp. PCC 6803
Author(s)
J Y Song; Hye Sun Cho; J I Cho; J S Jeon; J C Lagarias; Y I Park
Bibliographic Citation
Proceedings of National Academy of Sciences of United States of America, vol. 108, no. 26, pp. 10780-10785
Publication Year
2011
Abstract
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.
Keyword
PhytochromeTranscription regulatorTwo-component signalingUV-A sensor
ISSN
0027-8424
Publisher
Natl Acad Sciences
DOI
http://dx.doi.org/10.1073/pnas.1104242108
Type
Article
Appears in Collections:
Division of Research on National Challenges > Plant Systems Engineering Research > 1. Journal Articles
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