Transcriptional Activation of Quinoline Degradation Operons of Pseudomonas putida 86 by the AraC/XylS-Type Regulator OxoS and Cross-Regulation of the P qorM Promoter by XylS

Abstract

The quinoline-degradative gene cluster (oxoO, open reading frames 1 to 6 [ORF1 to -6], qorMSL, ORF7 to -9, oxoR) of Pseudomonas putida 86 consists of several overlapping operons controlled in response to quinoline by the master promoter PoxoO and internal promoters Porf3, PqorM, and PoxoR. ORF7 to -9, presumed to be important for maturation of the molybdenum hydroxylase quinoline 2-oxidoreductase, are also weakly transcribed independently of quinoline. Expression of the oxoS gene, located upstream of oxoO, is not influenced by the carbon source. OxoS shows 26% amino acid sequence identity to XylS, the transcriptional regulator of the meta pathway promoter Pm of TOL plasmid pWW0, and is required for quinoline-dependent transcription from PoxoO, Porf3, PqorM, and PoxoR. 5 deletion analysis of PoxoO and PqorM suggested that a 5-TGCPu CT-N 3 -GGGATA-3 motif, which resembles the distal 5-TGCA-N 6 -GGNTA-3 half-site of the tandem XylS binding site, is essential for oxoS-dependent transcriptional activation. PqorM, which shows similarity to the tandem XylS recognition site of Pm, was cross-activated by the xylS gene product in response to benzoate. The distal half-site of PqorM is necessary, but probably not sufficient, for transcriptional activation by XylS. Despite conservation in PoxoO of a distal 5-TGCA-N 6 -GGNTA-3 sequence, cross-activation of PoxoO by XylS and benzoate was not observed. The oxoS gene product in the presence of quinoline weakly stimulated transcription from the Pm promoter. Involvement of an XylS-type protein in the regulation of genes encoding synthesis of a molybdenum hydroxylase is without precedent and may reflect the evolutionary origin of this pathway in the metabolism of aromatic compounds.

The differential response of the Pben promoter of Pseudomonas putida mt‐2 to BenR and XylS prevents metabolic conflicts in m‐xylene biodegradation

“…Cross-activation between AraC-type regulators besides BenR/XylS has been reported (Ledger et al, 2002;Carl and Fetzner, 2005), indicating a degree of promiscuity in respect to operator binding specificities in this family of transcriptional factors. Such a cross-binding of activators to non-discriminating regulatory sequences surely plays a role in the evolution of novel catabolic routes, as it allows primal regulation of genes acquired by horizontal transfer (de Lorenzo and Perez-Martin, 1996).…”

Quinoline biodegradation and its nitrogen transformation pathway by a Pseudomonas sp. strain

“…Previous studies mainly focused on the biodegradation pathway (Shukla 1986(Shukla , 1989Brockman et al 1989) and degradation genes (Bläse et al 1996;Carl and Fetzner 2005). Although the metabolic pathway by strains of Pseudomonas has been studied intensively, the quantitative characteristics of the intermediates and the N transformation from quinoline remain unclear.…”

A finely tuned regulatory circuit of the nicotinic acid degradation pathway in Pseudomonas putida

“…Although the transcriptional studies of pathways for the degradation of aromatic compounds have been mainly focused in benzene‐related molecules, the catabolism of heterocyclic aromatic compounds is also under the control of similar systems as it has been reported for some pyridine derivatives (Sandu et al ., 2003; Carl and Fetzner, 2005; Chiribau et al ., 2005) and other N ‐heterocyclic compounds (Schultz et al ., 2001; Urata et al ., 2004; Porrúa et al ., 2010). Nicotinic acid (NA) is a carboxylic derivative of pyridine and is a widely distributed molecule that serves as sole carbon and nitrogen source for some bacteria and fungi (Kaiser et al ., 1996; Fetzner, 1998).…”