Briefly , pNL3 is a pBR322-derived reporter plasmid in which the PhoP-activated phoN promoter region of S. enterica serovar Typhimurium is fused to the lacZ structural gene .
We have investigated the transcriptional regulation and the interaction of the response regulator PhoP with the promoter regions of the PhoP-activated loci phoPQ , mgtA , slyB , pmrD , pcgL , phoN , pagC , and mgtCB .
PhoP-suppressed genes include prgH and fliC [ 55 -- 57 ] , PhoP-activated genes include pmrAB , another two-component signal transduction system involved primarily in the protection of Salmo-nella to cationic antimicrobial peptides ( CAMP , see below ) [ 58 ] , mgtA and mgtCB encoding Mg transport 2 + systems , phoN , a periplasmic non-specific acid phospha-tase , pcgL encoding a periplasmic D-Ala -- D-Ala dipeptidase , or pagL , pagP and pgtE which contribute to increased resistance to CAMPs [ 59 -- 62 ] .
RT-PCR analysis independently showed an NO-dependent downregulation in the transcription of PhoP-activated genes phoP , phoQ , mig-14 and phoN , while RNS treatment did not affect ( e.g. , rpoD ) or even increased ( e.g. , hmpA ) the expression of other loci ( fig. 5B ) .
Two additional PhoP-activated genes , slyB and phoN , were used as positive and negative controls , respectively , since previous experiments have shown direct interaction of PhoP with the promoter of slyB but not with the promoter of phoN ( 50 ) .