title: Disruption of MiaA provides insights into the regulation of phenazine biosynthesis under suboptimal growth conditions in Pseudomonas chlororaphis 30-84.
abstract: Many products of secondary metabolism are activated by quorum sensing (QS), yet even at cell densities sufficient for QS, their production may be repressed under suboptimal growth conditions via mechanisms that still require elucidation. For many beneficial plant-associated bacteria, secondary metabolites such as phenazines are important for their competitive survival and plant-protective activities. Previous work established that phenazine biosynthesis in Pseudomonas chlororaphis 30-84 is regulated by the PhzR/PhzI QS system, which in turn is regulated by transcriptional regulator Pip, two-component system RpeA/RpeB and stationary phase/stress sigma factor RpoS. Disruption of MiaA, a tRNA modification enzyme, altered primary metabolism and growth leading to widespread effects on secondary metabolism, including reduced phenazine production and oxidative stress tolerance. Thus, the miaA mutant provided the opportunity to examine the regulation of phenazine production in response to altered metabolism and growth or stress tolerance. Despite the importance of MiaA for translation efficiency, the most significant effect of miaA disruption on phenazine production was the reduction in the transcription of phzR, phzI and pip, whereas neither the transcription nor translation of RpeB, a transcriptional regulator of pip, was affected. Constitutive expression of rpeB or pip in the miaA mutant completely restored phenazine production, but it resulted in further growth impairment. Constitutive expression of RpoS alleviated sensitivity to oxidative stress resulting from RpoS translation inefficiency in the miaA mutant, but it did not restore phenazine production. Our results support the model that cells curtail phenazine biosynthesis under suboptimal growth conditions via RpeB/Pip-mediated regulation of QS.
authors.affiliation: Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX 77943-2133, USA.
authors.forename: Jun Myoung
authors.initials: JM
authors.lastname: Yu
authors.affiliation: Earth and Environmental Sciences, Los Alamos National Laboratory, Los Alamos, NM 87544, USA.
authors.forename: Dongping
authors.initials: D
authors.lastname: Wang
authors.affiliation: Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX 77943-2133, USA.
authors.forename: Leland S
authors.initials: LS
authors.lastname: Pierson
authors.affiliation: Department of Horticultural Sciences, Texas A&M University, College Station, TX 77943-2133, USA.|Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX 77943-2133, USA.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Pierson
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000235:genetics*; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics*; D018384:Oxidative Stress / Q000502:physiology*; D010453:Peptide Synthases / Q000235:genetics; D010619:Phenazines / Q000378:metabolism*; D000070096:Pseudomonas chlororaphis / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D053038:Quorum Sensing / Q000235:genetics* / Q000502:physiology; D012808:Sigma Factor / Q000096:biosynthesis / Q000235:genetics; D015534:Trans-Activators / Q000235:genetics; D014158:Transcription, Genetic / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D010619:Phenazines; C098602:PhzI protein, Pseudomonas sp.; C088011:PhzR protein, Pseudomonas; D012808:Sigma Factor; D015534:Trans-Activators; C000598831:phenazine; C069567:sigma factor KatF protein, Bacteria; D019883:Alkyl and Aryl Transferases; C024274:adenylate isopentenyltransferase; D010453:Peptide Synthases; C069262:pipecolate-activating enzyme