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PLoS One. 2015 Feb 6;10(2):e0117667. doi: 10.1371/journal.pone.0117667. eCollection 2015.

Genetic and genomic diversity studies of Acacia symbionts in Senegal reveal new species of Mesorhizobium with a putative geographical pattern.

Author information

1
Laboratoire Commun de Microbiologie IRD/ISRA/UCAD, Département de Biologie Végétale, Faculté des Sciences et Techniques, Université Cheikh Anta DIOP de Dakar, Centre de Recherche de Bel Air, Dakar, Senegal; Laboratoire Mixte International Adaptation des Plantes et Microorganismes Associés aux Stress Environnementaux (LAPSE), Dakar, Senegal; IRD-Laboratoire des Symbioses Tropicales et Méditerranéennes (LSTM), Campus de Baillarguet, Montpellier, France.
2
Laboratoire Commun de Microbiologie IRD/ISRA/UCAD, Département de Biologie Végétale, Faculté des Sciences et Techniques, Université Cheikh Anta DIOP de Dakar, Centre de Recherche de Bel Air, Dakar, Senegal; Laboratoire Mixte International Adaptation des Plantes et Microorganismes Associés aux Stress Environnementaux (LAPSE), Dakar, Senegal.
3
IRD-Laboratoire des Symbioses Tropicales et Méditerranéennes (LSTM), Campus de Baillarguet, Montpellier, France.
4
Laboratoire Mixte International Biotechnologie Microbienne et Végétale (LBMV), Rabat, Morocco.
5
Laboratoire Commun de Microbiologie IRD/ISRA/UCAD, Département de Biologie Végétale, Faculté des Sciences et Techniques, Université Cheikh Anta DIOP de Dakar, Centre de Recherche de Bel Air, Dakar, Senegal; Institut Sénégalais de Recherches Agricoles (ISRA), Dakar, Senegal.
6
Irstea, UR MALY, centre de Lyon-Villeurbanne, Villeurbanne, France.
7
MGX-Montpellier GenomiX, Institut de Génomique Fonctionnelle, Montpellier, France.
8
Institut Sénégalais de Recherches Agricoles (ISRA), Dakar, Senegal.
9
Laboratoire Mixte International Adaptation des Plantes et Microorganismes Associés aux Stress Environnementaux (LAPSE), Dakar, Senegal; IRD-Laboratoire des Symbioses Tropicales et Méditerranéennes (LSTM), Campus de Baillarguet, Montpellier, France.

Abstract

Acacia senegal (L) Willd. and Acacia seyal Del. are highly nitrogen-fixing and moderately salt tolerant species. In this study we focused on the genetic and genomic diversity of Acacia mesorhizobia symbionts from diverse origins in Senegal and investigated possible correlations between the genetic diversity of the strains, their soil of origin, and their tolerance to salinity. We first performed a multi-locus sequence analysis on five markers gene fragments on a collection of 47 mesorhizobia strains of A. senegal and A. seyal from 8 localities. Most of the strains (60%) clustered with the M. plurifarium type strain ORS 1032T, while the others form four new clades (MSP1 to MSP4). We sequenced and assembled seven draft genomes: four in the M. plurifarium clade (ORS3356, ORS3365, STM8773 and ORS1032T), one in MSP1 (STM8789), MSP2 (ORS3359) and MSP3 (ORS3324). The average nucleotide identities between these genomes together with the MLSA analysis reveal three new species of Mesorhizobium. A great variability of salt tolerance was found among the strains with a lack of correlation between the genetic diversity of mesorhizobia, their salt tolerance and the soils samples characteristics. A putative geographical pattern of A. senegal symbionts between the dryland north part and the center of Senegal was found, reflecting adaptations to specific local conditions such as the water regime. However, the presence of salt does not seem to be an important structuring factor of Mesorhizobium species.

PMID:
25658650
PMCID:
PMC4319832
DOI:
10.1371/journal.pone.0117667
[Indexed for MEDLINE]
Free PMC Article

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