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Roles of CmpR, a LysR family transcriptional regulator, in acclimation of the cyanobacterium Synechococcus sp. strain PCC 7942 to low‐CO 2 and high‐light conditions
Author(s) -
Takahashi Yukari,
Yamaguchi Osamu,
Omata Tatsuo
Publication year - 2004
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.1365-2958.2004.04021.x
Subject(s) - operon , biology , gene , mutant , promoter , transcription (linguistics) , transcription factor , genetics , synechococcus , microbiology and biotechnology , gene expression , cyanobacteria , bacteria , linguistics , philosophy
Summary The cmp operon of Synechococcus sp. strain PCC 7942, encoding a high‐affinity bicarbonate transporter, is induced under low CO 2 conditions by a LysR family protein CmpR. CmpR was found to be required also for induction of the operon by transfer of the cells from low‐light to high‐light conditions, indicating involvement of a common mechanism in the high‐light‐ and low‐CO 2 ‐responsive regulation. Expression of the high‐light inducible genes psbAII and psbAIII , on the other hand, was found to be induced also by low‐CO 2 conditions. A single promoter was responsible for the high‐light and low‐CO 2 induction of each of psbAII and psbAIII , suggesting involvement of a common regulatory mechanism in the light and CO 2 responses of the psbA genes. CmpR was, however, not required for the induction of psbAII and psbAIII , indicating the presence of multiple mechanisms for induction of genes under high‐light and low‐CO 2 conditions. The CmpR‐deficient mutant nevertheless showed lower levels of the psbAII and psbAIII transcripts than the wild‐type strain under all the light and CO 2 conditions examined. Gel shift assays showed that CmpR binds to the enhancer elements of psbAII and psbAIII , through specific interaction with a sequence signature conforming to the binding motif of similar LysR family proteins. These findings showed that CmpR acts as a trans ‐acting factor that enhances transcription of the photosystem II genes involved in acclimation to high light, revealing a complex network of gene regulation in the cyanobacterium.