The Pseudomonas aeruginosa Two-Component Regulator AlgR Directly Activates rsmA Expression in a Phosphorylation-Independent Manner

Abstract

Pseudomonas aeruginosa is an important pathogen of the immunocompromised, causing both acute and chronic infections. In cystic fibrosis (CF) patients, P. aeruginosa causes chronic disease. The impressive sensory network of P. aeruginosa allows the bacterium to sense and respond to a variety of stimuli found in diverse environments. Transcriptional regulators, including alternative sigma factors and response regulators, integrate signals changing gene expression, allowing P. aeruginosa to cause infection. The two-component transcriptional regulator AlgR is important in P. aeruginosa pathogenesis in both acute and chronic infections. In chronic infections, AlgR and the alternative sigma factor AlgU activate the genes responsible for alginate production. Previous work demonstrated that AlgU controls rsmA expression. RsmA is a posttranscriptional regulator that is antagonized by two small RNAs, RsmY and RsmZ. In this work, we demonstrate that AlgR directly activates rsmA expression from the same promoter as AlgU. In addition, phosphorylation was not necessary for AlgR activation of rsmA using algR and algZ mutant strains. AlgU and AlgR appear to affect the antagonizing small RNAs rsmY and rsmZ indirectly. RsmA was active in a mucA22 mutant strain using leader fusions of two RsmA targets, tssA1 and hcnA. AlgU and AlgR were necessary for posttranscriptional regulation of tssA1 and hcnA. Altogether, our work demonstrates that the alginate regulators AlgU and AlgR are important in the control of the RsmA posttranscriptional regulatory system. These findings suggest that RsmA plays an unknown role in mucoid strains due to AlgU and AlgR activities.IMPORTANCE P. aeruginosa infections are difficult to treat and frequently cause significant mortality in CF patients. Understanding the mechanisms of persistence is important. Our work has demonstrated that the alginate regulatory system also significantly impacts the posttranscriptional regulator system RsmA/Y/Z. We demonstrate that AlgR directly activates rsmA expression, and this impacts the RsmA regulon. This leads to the possibility that the RsmA/Y/Z system plays a role in helping P. aeruginosa persist during chronic infection. In addition, this furthers our understanding of the reach of the alginate regulators AlgU and AlgR.KEYWORDS P. aeruginosa, RsmA, AlgR, mucoid, Pseudomonas aeruginosa, cystic fibrosis, mucA, two-component regulatory systems T he opportunistic pathogen Pseudomonas aeruginosa possesses multiple virulence factors for causing disease. This allows P. aeruginosa to cause both acute and chronic infections. Acute infecting strains are characterized by the presence of type IV pili (T4P), flagella, and a type III secretion system (T3SS) (1-3). In contrast, chronic infecting strains diversify (4, 5) and frequently do not express T3SS, T4P, or flagella (6, 7). Chronic infecting strains often form biofilms composed of exopolysaccharides, such as alginate, and signal a decline in lung function in CF patients (8-11). Alginate

The Stringent Stress Response Controls Proteases and Global Regulators under Optimal Growth Conditions in Pseudomonas aeruginosa

“…The zinc-dependent protease PA0277 (5.2-fold downregulated by SHX induction, 9.9-fold upregulated in the mutant) is directly controlled by the posttranscriptional regulator RsmA ( 59 ), and the expression of rsmA is directly activated by AlgR ( 60 ) and indirectly via GacA through RsmY and RsmZ ( 61 ). The response regulators AlgR and GacA were controlled by the stringent stress response under normal conditions.…”

Pseudomonas aeruginosa type IV minor pilins and PilY1 regulate virulence by modulating FimS-AlgR activity

“…When algR was expressed in trans from a multicopy plasmid in PA14 algR , killing was delayed compared to the vector control ( Fig 6A ). Because un-phosphorylated AlgR can also affect transcription of a subset of genes [ 66 , 67 ], we tested the same mutant complemented with AlgR D54A . Complementation of the algR mutant with AlgR D54A resulted in a severe delay in killing relative to the vector-only control.…”

Pseudomonas aeruginosa AlgR Phosphorylation Status Differentially Regulates Pyocyanin and Pyoverdine Production

“…There is additional overlap between the RsmA- rsmY/Z and AlgZR regulatory systems with pyoverdine production ( 77 ). Conflicting data suggest that AlgZR may play a role in expression of rsmA and rsmY/Z ( 78 – 80 ), which may be a result of strain differences, e.g., AlgR’s effect on mucoid versus nonmucoid strains. While RsmA- rsmY/Z and prrf1 and prrf2 have been shown to influence production of siderophores, additional RNA mechanisms control other aspects of iron acquisition, including the readthrough of prrf1 and prrf2 , which produces prrH , a heme regulatory mechanism.…”