Investigation of the quorum-sensing regulation of P. aeruginoas PAO1 gene rhlI began with identification of the transcriptional start site via primer extension. The same assay showed reduced transcription in a lasR-mutant strain. A putative las-box was identified from comparison with lux-box sequences. Beta-gal assay was applied to five mutant strains for comparison with wild-type expression: lasR-, lasI-, rhlR-, rhlI-, and lasI-/rhlI-. Mutant strains lasR-, lasI-, and lasI-/rhlI- showed dramatic loss of expression, while levels in rhlR- and rhlI- strains did not fall below 75% of the wild-type, indicating primary regulation by the lasR/lasI system. Addition of respective autoinducers restored expression in lasI- and rhlI- mutants. Assays were repeated with partial las-box deletions in all strains, and expression fell dramatically in all five and the wild-type.
Regulated genes for each binding site are displayed below. Gene regulation diagrams show binding sites, positively-regulated genes, negatively-regulated genes, both positively and negatively regulated genes, genes with unspecified type of regulation. For each indvidual site, experimental techniques used to determine the site are also given.
|Site sequence||Regulated genes||Gene diagram||Experimental techniques||TF function||TF type|