Cell-to-Cell and Long Distance Signaling
Rajamani, Sathish , Teplitski, Max , Robinson, Jayne B. , Gao, Mengsheng , Phillips, Donald A. , Bauer, Dietz .
The LasR Quorum Sensing Receptor Recognizes the Vitamin Riboflavin and Its Derivative Lumichrome as well as the Cognate Acyl Homoserine Lactone Signal.
N-acyl homoserine lactones (AHLs) are commonly employed as intercellular signals by gram-negative bacteria for quorum sensing regulation of gene expression. These AHL signals are recognized by members of the LuxR family of receptor proteins. Based on bacterial reporter studies, plants, algae and fungi have been shown to produce an array of compounds that can act as agonists or antagonists of LuxR receptors, mimicking bacterial AHL signals. We chemically identified lumichrome in culture filtrates of the unicellular green alga Chlamydomonas reinhardtii as a potent agonist of the LasR AHL receptor from Pseudomonas aeruginosa. Lumichrome is a catabolite of the vitamin riboflavin. Riboflavin also acted as an agonist of the LasR receptor. LasR was activated to comparable levels by 80-300 picomolar concentrations of riboflavin, lumichrome and the cognate AHL (3-oxo-C12-homoserine lactone). Deletion of the AHL binding domain of the LasR receptor protein abolished responses to both the cognate AHL and to lumichrome/riboflavin. Mutant derivatives of LasR were generated by substituting three amino acids plausibly required for hydrogen bonding of LasR to the furanone ring of AHLs. Each amino acid substitution abolished/diminished the ability of lumichrome, riboflavin and 3-oxo-C12-HSL to activate LasR-dependent gene expression. Based on these results, it appears that LuxR quorum sensing receptors such as LasR recognize lumichrome and riboflavin in the same way and to much the same extent as they recognize AHLs. These findings raise questions as to whether vitamins and derivatives also serve as quorum sensing signals and whether other bacterial metabolites might be recognized by “AHL” receptors.
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1 - University of California - Davis, Plant Science, Mail Stop # 1, One Shields Avenue, Dept of Plant and Environmenta, Davis, CA, 95616, USA
2 - University of Florida, Department of Soil and Water Science
3 - University of Dayton, Biology Department
4 - University of California - Davis, Plant Science
N-acyl homoserine lactone
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM