Mapping the TSSs and promoters of <i>pltR</i> and <i>pltL</i> genes through 5′RACE and the above <i>lacZ</i> reporter analysis (Fig. 1).

<p>P_R, the <i>pltR</i> promoter; P_L, the <i>pltLp</i> which needs to be specifically activated by PltR; P_X, a non-PltR controlled promoter closely neighboring the upstream of P_L; P_Y, another potential promoter silent in <i>P. aeruginosa</i> M18, but active in <i>E. coli</i> DH5α. The TSS (+1) of the <i>pltR</i> transcript was located at 63 bp upstream of the <i>pltR</i> translational start codon ATG, which is identical to the predicted +1 site. The TSS of the <i>plt</i> operon was located at 46 bp upstream of the <i>pltL</i> ATG. Closely linked to the <i>pltLp</i> with the P_x promoter, a palindromic <i>lys</i> box, including two 9 bp inverted complementary sequences separated by 4 bases, is boxed and highlighted by two head-to-head arrows.