title: Pseudomonas fluorescensTransportome Is Linked to Strain-Specific Plant Growth Promotion in Aspen Seedlings under Nutrient Stress.
abstract: Diverse communities of bacteria colonize plant roots and the rhizosphere. Many of these rhizobacteria are symbionts and provide plant growth promotion (PGP) services, protecting the plant from biotic and abiotic stresses and increasing plant productivity by providing access to nutrients that would otherwise be unavailable to roots. In return, these symbiotic bacteria receive photosynthetically-derived carbon (C), in the form of sugars and organic acids, from plant root exudates. PGP activities have been characterized for a variety of forest tree species and are important in C cycling and sequestration in terrestrial ecosystems. The molecular mechanisms of these PGP activities, however, are less well-known. In a previous analysis ofPseudomonasgenomes, we found that the bacterial transportome, the aggregate activity of a bacteria's transmembrane transporters, was most predictive for the ecological niche of Pseudomonads in the rhizosphere. Here, we usedPopulus tremuloidesMichx. (trembling aspen) seedlings inoculated with one of threePseudomonas fluorescensstrains (Pf0-1, SBW25, and WH6) and onePseudomonas protegens(Pf-5) as a laboratory model to further investigate the relationships between the predicted transportomic capacity of a bacterial strain and its observed PGP effects in laboratory cultures. Conditions of low nitrogen (N) or low phosphorus (P) availability and the corresponding replete media conditions were investigated. We measured phenotypic and biochemical parameters ofP. tremuloidesseedlings and correlatedP. fluorescensstrain-specific transportomic capacities withP. tremuloidesseedling phenotype to predict the strain and nutrient environment-specific transporter functions that lead to experimentally observed, strain, and media-specific PGP activities and the capacity to protect plants against nutrient stress. These predicted transportomic functions fall in three groups: (i) transport of compounds that modulate aspen seedling root architecture, (ii) transport of compounds that help to mobilize nutrients for aspen roots, and (iii) transporters that enable bacterial acquisition of C sources from seedling root exudates. These predictions point to specific molecular mechanisms of PGP activities that can be directly tested through future, hypothesis-driven biological experiments.
authors.affiliation: Biosciences Division, Argonne National Laboratory Lemont, IL, USA.
authors.forename: Shalaka
authors.initials: S
authors.lastname: Shinde
authors.affiliation: Department of Biology, West Virginia University Morgantown, WV, USA.
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Cumming
authors.affiliation: Biosciences Division, Argonne National Laboratory Lemont, IL, USA.
authors.forename: Frank R
authors.initials: FR
authors.lastname: Collart
authors.affiliation: Biosciences Division, Argonne National Laboratory Lemont, IL, USA.
authors.forename: Philippe H
authors.initials: PH
authors.lastname: Noirot
authors.affiliation: Biosciences Division, Argonne National LaboratoryLemont, IL, USA; Department of Bioengineering, University of Illinois at ChicagoChicago, IL, USA.
authors.forename: Peter E
authors.initials: PE
authors.lastname: Larsen
keywords: Pseudomonas; aspen; computational modeling; nitrogen; phosphorus; plant growth promotion; transportomics