Duplication of Plasmid-Borne Nitrite Reductase Gene nirK in the Wheat-Associated Plant Growth–Promoting Rhizobacterium Azospirillum brasilense Sp245 - INRAE - Institut national de recherche pour l’agriculture, l’alimentation et l’environnement Accéder directement au contenu
Article Dans Une Revue Molecular Plant-Microbe Interactions Année : 2008

Duplication of Plasmid-Borne Nitrite Reductase Gene nirK in the Wheat-Associated Plant Growth–Promoting Rhizobacterium Azospirillum brasilense Sp245

Résumé

In the plant growth–promoting rhizobacterium Azospirillum brasilense Sp245, nitric oxide produced by denitrification could be a signal involved in stimulation of root branching, and the dissimilatory nitrite reductase gene nirK is upregulated on wheat roots. Here, it was found that Sp245 did not contain one copy of nirK but two (named nirK1 and nirK2), localized on two different plasmids, including one plasmid prone to rearrangements. Their deduced protein sequences displayed 99.2% identity but their promoter regions and upstream genetic environment differed. Phylogenetic studies revealed that nirK1 and nirK2 clustered next to most β-proteobacterial sequences rather than in the vicinity of other Azospirillum spp. and most α-proteobacterial sequences, regardless of whether DNA or deduced protein sequences were used. This points to past horizontal gene transfers. Analysis of the number of nonsynonymous and synonymous substitutions per site indicated that nirK has been subjected to neutral selection in bacteria. The use of transcriptional fusions with egfp, encoding an enhanced green fluorescent protein variant, revealed that both nirK1 and nirK2 promoter regions were upregulated in vitro under microaerobiosis or the presence of nitrite as well as on wheat roots. The analysis of nirK1 and nirK2 mutants revealed that the two genes were functional. Overall, results suggest that nirK has been acquired horizontally by A. brasilense Sp245 from a distant relative and underwent subsequent duplication; however, both paralogs remained functional and retained their upregulation by the plant partner.
Fichier principal
Vignette du fichier
MPMI-19-0502_1.pdf (551.49 Ko) Télécharger le fichier
Origine : Fichiers produits par l'(les) auteur(s)
Loading...

Dates et versions

halsde-00344099 , version 1 (29-05-2020)

Identifiants

Citer

Joël F. Pothier, Claire Prigent-Combaret, Jacqueline Haurat, Yvan Moënne-Loccoz, Florence Wisniewski-Dyé. Duplication of Plasmid-Borne Nitrite Reductase Gene nirK in the Wheat-Associated Plant Growth–Promoting Rhizobacterium Azospirillum brasilense Sp245. Molecular Plant-Microbe Interactions, 2008, 21 (6), pp.831-842. ⟨10.1094/MPMI⟩. ⟨halsde-00344099⟩
71 Consultations
34 Téléchargements

Altmetric

Partager

Gmail Facebook X LinkedIn More