title: Negative regulation of germination-arrest factor production in Pseudomonas fluorescens WH6 by a putative extracytoplasmic function sigma factor.
abstract: Pseudomonas fluorescens WH6 secretes a germination-arrest factor (GAF) that we have identified previously as 4-formylaminooxyvinylglycine. GAF irreversibly inhibits germination of the seeds of numerous grassy weeds and selectively inhibits growth of the bacterial plant pathogen Erwinia amylovora. WH6-3, a mutant that has lost the ability to produce GAF, contains a Tn5 insertion in prtR, a gene that has been described previously in some strains of P. fluorescens as encoding a transmembrane regulator. As in these other pseudomonads, in WH6, prtR occurs immediately downstream of prtI, which encodes a protein homologous to extracytoplasmic function (ECF) sigma factors. These two genes have been proposed to function as a dicistronic operon. In this study, we demonstrated that deletion of prtI in WT WH6 had no effect on GAF production. However, deletion of prtI in the WH6-3 mutant overcame the effects of the Tn5 insertion in prtR and restored GAF production in the resulting double mutant. Complementation of the double prtIR mutant with prtI suppressed GAF production. This overall pattern of prtIR regulation was also observed for the activity of an AprX protease. Furthermore, reverse transcription quantitative real-time PCR analysis demonstrated that alterations in GAF production were mirrored by changes in the transcription of two putative GAF biosynthetic genes. Thus, we concluded that PrtI exerted a negative regulatory effect on GAF production, although the mechanism has not yet been determined. In addition, evidence was obtained that the transcription of prtI and prtR in WH6 may be more complex than predicted by existing models.
authors.affiliation: Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331, USA.
authors.forename: Rachel A
authors.initials: RA
authors.lastname: Okrent
authors.affiliation: USDA-ARS National Forage Seed Production Research Center, Corvallis, OR 97331, USA.
authors.forename: Anne B
authors.initials: AB
authors.lastname: Halgren
authors.affiliation: USDA-ARS National Forage Seed Production Research Center, Corvallis, OR 97331, USA.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Azevedo
authors.affiliation: Center for Genome Research and Biocomputing, Oregon State University, Corvallis, OR 97331, USA.|Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331, USA.
authors.forename: Jeff H
authors.initials: JH
authors.lastname: Chang
authors.affiliation: Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331, USA.
authors.forename: Dallice I
authors.initials: DI
authors.lastname: Mills
authors.affiliation: USDA-ARS National Forage Seed Production Research Center, Corvallis, OR 97331, USA.
authors.forename: Maciej
authors.initials: M
authors.lastname: Maselko
authors.affiliation: Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331, USA.
authors.forename: Donald J
authors.initials: DJ
authors.lastname: Armstrong
authors.affiliation: USDA-ARS National Forage Seed Production Research Center, Corvallis, OR 97331, USA.
authors.forename: Gary M
authors.initials: GM
authors.lastname: Banowetz
authors.affiliation: USDA-ARS National Forage Seed Production Research Center, Corvallis, OR 97331, USA.
authors.forename: Kristin M
authors.initials: KM
authors.lastname: Trippe
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D009876:Operon; D011551:Pseudomonas fluorescens / Q000235:genetics / Q000378:metabolism*; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D012808:Sigma Factor