AUTHOR=Fang Yun-Ling , Chen Bo , Zhou Lian , Jin Zi-Jing , Sun Shuang , He Ya-Wen 

TITLE=The Anti-activator QslA Negatively Regulates Phenazine-1-Carboxylic Acid Biosynthesis by Interacting With the Quorum Sensing Regulator MvfR in the Rhizobacterium Pseudomonas aeruginosa Strain PA1201

JOURNAL=Frontiers in Microbiology

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2018.01584

DOI=10.3389/fmicb.2018.01584

ISSN=1664-302X

ABSTRACT=<p>Two almost identical gene clusters (<italic>phz1</italic> and <italic>phz2</italic>) are responsible for phenazine-1-carboxylic acid (PCA) production in <italic>Pseudomonas aeruginosa</italic> (<italic>P</italic>. <italic>aeruginosa</italic>) strain MSH (derived from strain PA1201). Here, we showed that the anti-activator QslA negatively regulated PCA biosynthesis and <italic>phz1</italic> expression in strain PA1201 but had little effect on <italic>phz2</italic> expression. This downregulation was mediated by a 56-bp region within the 5′-untranslated region (5′-UTR) of the <italic>phz1</italic> promoter and was independent of LasR and RsaL signaling. QslA also negatively regulated <italic>Pseudomonas</italic> quinolone signal (PQS) production. Indeed, QslA controlled the PQS threshold concentration needed for PQS-dependent PCA biosynthesis. The quorum sensing regulator MvfR was required for the QslA-dependent inhibition of PCA production. We identified a direct protein–protein interaction between QslA and MvfR. The ligand-binding domain of MvfR (residues 123–306) was involved in this interaction. Our results suggested that MvfR bound directly to the promoter of the <italic>phz1</italic> cluster. QslA interaction with MvfR prevented the binding of MvfR to the <italic>phz1</italic> promoter regions. Thus, this study depicted a new mechanism by which QslA controls PCA and PQS biosynthesis in <italic>P</italic>. <italic>aeruginosa</italic>.</p>