Nitrate-dependent control of root architecture and N nutrition are altered by a plant growth-promoting Phyllobacterium sp |
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Authors: | Sophie Mantelin Guilhem Desbrosses Marièle Larcher Timothy J. Tranbarger Jean-Claude Cleyet-Marel Bruno Touraine |
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Affiliation: | (1) Laboratoire des Symbioses Tropicales et Méditerranéennes, Unité Mixte de Recherches (UMR) 113 (Université Montpellier II, Institut de Recherche pour le Développement, Centre de Coopération Internationale en Recherche Agronomique pour le Développement, Agro-M), Institut National de la Recherche Agronomique (Unité Sous Contrat 1042), Université Montpellier II, CC 002, Place Eugène Bataillon, 34095 Montpellier cedex 05, France;(2) Present address: Observatoire Océanologique de Banyuls, UMR 7621, , BP 44, 66651 Banyuls sur Mer Cedex, France;(3) Present address: Centre de Recherche CIRAD, IRD de Montpellier, Laboratoire GeneTrop, BP 5045, 34032 Montpellier, France |
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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. |
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Keywords: | Arabidopsis N transporter N uptake Nitrate availability Plant growth-promoting rhizobia— Root development |
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