title: Nitrate-dependent control of root architecture and N nutrition are altered by a plant growth-promoting Phyllobacterium sp.
abstract: Both root architecture and plant N nutrition are altered by inoculation with the plant growth-promoting rhizobacteria (PGPR) Phyllobacterium strain STM196. It is known that NO3- and N metabolites can act as regulatory signals on root development and N transporters. In this study, we investigate the possible interrelated effects on root development and N transport. We show that the inhibition of Arabidopsis lateral root growth by high external NO3- is overridden by Phyllobacterium inoculation. However, the leaf NO3- pool remained unchanged in inoculated plants. By contrast, the Gln root pool was reduced in inoculated plants. Unexpectedly, NO3- influx and the expression levels of AtNRT1.1 and AtNRT2.1 genes coding for root NO3- transporters were also decreased after 8 days of Phyllobacterium inoculation. Although the mechanisms by which PGPR exert their positive effects remain unknown, our data show that they can optimize plant development independently from N supply, thus alleviating the regulatory mechanisms that operate in axenic conditions. In addition, we found that Phyllobacterium sp. elicited a very strong induction of AtNRT2.5 and AtNRT2.6, both genes preferentially expressed in the shoots whose functions are unknown.
authors.affiliation: UMR 113 (Institut de Recherche pour le Développement, Centre de Coopération Internationale en Recherche Agronomique pour le Développement, Agro-M), Université Montpellier II, Montpellier, France.
authors.forename: Sophie
authors.initials: S
authors.lastname: Mantelin
authors.forename: Guilhem
authors.initials: G
authors.lastname: Desbrosses
authors.forename: Marièle
authors.initials: M
authors.lastname: Larcher
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Tranbarger
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Cleyet-Marel
authors.forename: Bruno
authors.initials: B
authors.lastname: Touraine
mesh_terms: D020561:Alphaproteobacteria / Q000502:physiology*; D000596:Amino Acids / Q000378:metabolism; D027321:Anion Transport Proteins / Q000235:genetics / Q000378:metabolism; D017360:Arabidopsis / Q000254:growth & development / Q000378:metabolism / Q000382:microbiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D050901:Nitrate Reductase / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism; D010940:Plant Proteins; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism / Q000382:microbiology*; D018520:Plant Shoots / Q000254:growth & development / Q000378:metabolism / Q000382:microbiology
chemical_list: D000596:Amino Acids; D027321:Anion Transport Proteins; D029681:Arabidopsis Proteins; D050901:Nitrate Reductase; D009566:Nitrates; D009584:Nitrogen; D010940:Plant Proteins; C477335:NRT2.1 protein, Arabidopsis; C101492:NRT1.1 protein, Arabidopsis; C583321:NRT2.5 protein, Arabidopsis