Premium
Lactobacillus brevis responds to flavonoids through KaeR, a LysR‐type of transcriptional regulator
Author(s) -
Pande Santosh G.,
Pagliai Fernando A.,
Gardner Christopher L.,
Wrench Algevis,
Narvel Raed,
Gonzalez Claudio F.,
Lorca Graciela L.
Publication year - 2011
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.1365-2958.2011.07796.x
Subject(s) - biology , regulator , transcriptional regulation , lactobacillus brevis , lactobacillus , type (biology) , microbiology and biotechnology , genetics , bacteria , gene , transcription factor , ecology , lactobacillus plantarum , lactic acid
Summary The ability of transcription factors to respond to flavonoids as signal molecules was investigated in Lactobacillus brevis . Through in vitro screening of a small library of flavonoids, LVIS1989 (KaeR), a LysR‐type transcriptional regulator (LTTR), was identified as responsive to kaempferol. The modulation of KaeR activity by flavonoids was characterized in vivo and in vitro . DNase I footprint assays identified the binding of KaeR at two distinctive sites, one in the intergenic region between LVIS1988 and kaeR (−39 to +2) and another within LVIS1988 (−314 to −353, from kaeR translational start point). EMSA assays revealed that both binding sites are required for KaeR binding in vitro . Furthermore, KaeR–DNA interactions were stabilized by the addition of kaempferol (20 µM). In vivo qRT‐PCR experiments performed in L. brevis confirmed that the divergently transcribed genes LVIS1988 , LVIS1987 and LVIS1986 and kaeR are upregulated in the presence of kaempferol, indicating the role of KaeR as a transcriptional activator. Transcriptional lacZ fusions using Bacillus subtilis as a surrogate host showed that expression of kaeR and LVIS1988 were induced by the presence of the flavonoid. These results indicate that KaeR belongs to a small and poorly understood group of LTTRs that are positively autoregulated in the presence of a ligand.