Genome-Wide Analysis of Light Sensing In Prochlorococcus
Steglich C, Futschik M, Rector T, Steen R, Chisholm SW
J Bacteriol. 2006 Nov;188(22):7796-806. Epub 2006 Sep 15.
MED4 has, with a total of only 1,716 annotated
protein-coding genes, the most compact genome of a free-living
photoautotroph. Although light quality and quantity play an important role
in regulating the growth rate of this organism in its natural habitat, the
majority of known light-sensing proteins are absent from its genome. To
explore the potential for light sensing in this phototroph, we measured
its global gene expression pattern in response to different light
qualities and quantities by using high-density Affymetrix microarrays.
Though seven different conditions were tested, only blue light elicited a
strong response. In addition, hierarchical clustering revealed that the
responses to high white light and blue light were very similar and
different from that of the lower-intensity white light, suggesting that
the actual sensing of high light is mediated via a blue-light receptor.
Bacterial cryptochromes seem to be good candidates for the blue-light
sensors. The existence of a signaling pathway for the redox state of the
photosynthetic electron transport chain was suggested by the presence of
genes that responded similarly to red and blue light as well as genes that
responded to the addition of DCMU
[3-(3,4-dichlorophenyl)-1,1-N-N'-dimethylurea], a specific inhibitor of
photosystem II-mediated electron transport.
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