Premium
A light regulated OmpR‐class promoter element co‐ordinates light‐harvesting protein and chromophore biosynthetic enzyme gene expression
Author(s) -
Alvey Richard M.,
Bezy Ryan P.,
FrankenbergDinkel Nicole,
Kehoe David M.
Publication year - 2007
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2007.05656.x
Subject(s) - phycocyanobilin , biology , phytochrome , promoter , transcription (linguistics) , transcription factor , phycocyanin , operon , biliverdin , gene , gene expression , biochemistry , genetics , enzyme , heme , cyanobacteria , red light , botany , heme oxygenase , mutant , bacteria , linguistics , philosophy
Summary Co‐ordination of chromophore and apoprotein biosynthesis is required during photosynthetic light‐harvesting antennae production, such as occurs during complementary chromatic adaptation (CCA). This response to ambient light colour changes is controlled by a phytochrome‐class photoreceptor and involves changes in the synthesis of cyanobacterial light‐harvesting antennae. During growth in red light, CCA activates cpc2 transcription, an operon that encodes the light‐harvesting protein phycocyanin. In order to function, this apoprotein must have covalently attached phycocyanobilin chromophores, which are synthesized by PcyA. We show that pcyA is also transcriptionally activated by CCA during red light growth and is not regulated via feedback that senses cpc2 RNA levels. The pcyA and cpc2 promoters contain a common regulatory element, a direct repeat typical of OmpR‐class transcription factor binding sites, at similar positions relative to their red light‐controlled transcription start sites. Deletion of this element from the pcyA promoter eliminated CCA‐regulated transcription, and insertion of the element into a non‐light responsive promoter conferred CCA regulation. We conclude that this element is necessary and sufficient to confer CCA transcriptional regulation and that it co‐ordinates phycocyanin and phycocyanobilin biosynthesis in red light.