The signaling peptide PapR is required for the activity of the quorum-sensor PlcRa in Bacillus thuringiensis

Abstract

The transcriptional regulator PlcR, its cognate cell-cell signaling heptapeptide PapR7, and the oligopeptide permease OppABCDF, required for PapR7 import, form a quorum-sensing system that controls the expression of virulence factors in Bacillus cereus and Bacillus thuringiensis species. In B. cereus strain ATCC 14579, the transcriptional regulator PlcRa activates the expression of abrB2 gene, which encodes an AbrB-like transcriptional regulator involved in cysteine biosynthesis. PlcRa is a structural homolog of PlcR: in particular, its C-terminal TPR peptide-binding domain could be similarly arranged as in PlcR. The signaling peptide of PlcRa is not known. As PlcRa is a PlcR-like protein, the cognate PapR7 peptide (ADLPFEF) is a relevant candidate to act as a signaling peptide for PlcRa activation. Also, the putative PapRa7 peptide (CSIPYEY), encoded by the papRa gene adjacent to the plcRa gene, is a relevant candidate as addition of synthetic PapRa7 induces a dose-dependent increase of abrB2 expression. To address the issue of peptide selectivity of PlcRa, the role of PapR and PapRa peptides in PlcRa activity was investigated in B. thuringiensis 407 strain, by genetic and functional complementation analyses. A transcriptional fusion between the promoter of abrB2 and lacZ was used to monitor the PlcRa activity in various genetic backgrounds. We demonstrated that PapR was necessary and sufficient for PlcRa activity. We showed that synthetic PapRs from pherogroups II, III and IV and synthetic PapRa7 were able to trigger abrB2 expression, suggesting that PlcRa is less selective than PlcR. Lastly, the mode of binding of PlcRa was addressed using an in silico approach. Overall, we report a new role for PapR as a signaling peptide for PlcRa activity and show a functional link between PlcR and PlcRa regulons in B. thuringiensis .

Monoclonal Antibody HlyIIC‑15 to C-End Domain HlyII B. cereus Interacts with the Trombin Recognition Site

“…To confirm the epitope of the recognized HlyIIC-15, immunoblotting, wherein the interaction of antibodies along with HlyIICTD with recombinant proteins PlcR [9], HlyII, the deletion variant HlyIIΔC and HlyIIR (hemolysin II repressor) [10], as well as native hemolysin II B. cereus B771 cloned in Bacillus subtilis BD170 (Table 2), was used. In Fig.…”

The Food Poisoning Toxins of Bacillus cereus

“…Interestingly, newer studies have found a second quorum-sensing-system, consisting of PlcR-paralog PlcRa and the signaling peptide PapRa 7 , which is involved in oxidative stress response and cysteine metabolism. PapR variants were also able to activate PlcRa, which showed a connection between the PlcR and PlcRa regulons for the first time [250,251]. Recent studies focus on the inactivation of the PlcR-PapR quorum sensing system and, thus, the inhibition of virulence factor production due to synthetic PapR 7 derivatives.…”

Rap-Phr Systems from Plasmids pAW63 and pHT8-1 Act Together To Regulate Sporulation in the Bacillus thuringiensis Serovar kurstaki HD73 Strain

“…However, a notable exception has been observed recently with the B. thuringiensis PlcRa regulator, a structural paralog displaying 29% sequence identity with PlcR (61). This RNPP regulator, involved in the oxidative stress response and cysteine metabolism, is activated during stationary phase by PapR, the cognate signaling peptide of PlcR, suggesting a high and unexpected versatility of PlcRa (62).…”