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. 2016 Jul 26;6:30352. doi: 10.1038/srep30352

Figure 7. A schematic model for the effect of four QS systems on the expression of the phz1 and phz2 gene clusters.

Figure 7

The 3-oxo-C12-HSL/LasR system is located at the top of the signaling hierarchy and acts as a global regulator to affect diverse biological activities. It positively regulates C4-HSL production and differentially regulates the expression of both phz clusters. At early growth stages, LasR positively regulates the expression of phz1 and phz2, promoting PCA production; at late growth stages, it negatively regulates the expression of phz1 and phz2, repressing PCA production. Both the C4-HSL/RhlR and PQS/MvfR systems positively regulate the expression of phz1 and phz2, promoting PCA production. The C4-HSL/RhlR system slightly represses PQS production in PA1201. The IQS/IqsR system has no effects on other QS systems and does not regulate the expression of phz1 or phz2 in PA1201. Arrows indicate positive regulation, and the blunt ends denote negative regulation. The positive regulation of LasR at an early growth stage is indicated by black arrow with “E” for “Early stage”. The negative regulation of LasR at later stage is indicated by purple blunt end with “L” for “Late stage”.