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Search for Ancestral Features in Genomes of Rhizobium leguminosarum bv. viciae Strains Isolated from the Relict Legume Vavilovia formosa.

Abstract：

:Vavilovia formosa is a relict leguminous plant growing in hard-to-reach habitats in the rocky highlands of the Caucasus and Middle East, and it is considered as the putative closest living relative of the last common ancestor (LCA) of the Fabeae tribe. Symbionts of Vavilovia belonging to Rhizobium leguminosarum bv. viciae compose a discrete group that differs from the other strains, especially in the nucleotide sequences of the symbiotically specialised (sym) genes. Comparison of the genomes of Vavilovia strains with the reference group composed of R. leguminosarum bv. viciae strains isolated from Pisum and Vicia demonstrated that the vavilovia strains have a set of genomic features, probably indicating the important stages of microevolution of the symbiotic system. Specifically, symbionts of Vavilovia (considered as an ancestral group) demonstrated a scattered arrangement of sym genes (>90 kb cluster on pSym), with the location of nodT gene outside of the other nod operons, the presence of nodX and fixW, and the absence of chromosomal fixNOPQ copies. In contrast, the reference (derived) group harboured sym genes as a compact cluster (<60 kb) on a single pSym, lacking nodX and fixW, with nodT between nodN and nodO, and possessing chromosomal fixNOPQ copies. The TOM strain, obtained from nodules of the primitive "Afghan" peas, occupied an intermediate position because it has the chromosomal fixNOPQ copy, while the other features, the most important of which is presence of nodX and fixW, were similar to the Vavilovia strains. We suggest that genome evolution from the ancestral to the derived R. leguminosarum bv. viciae groups follows the "gain-and-loss of sym genes" and the "compaction of sym cluster" strategies, which are common for the macro-evolutionary and micro-evolutionary processes. The revealed genomic features are in concordance with a relict status of the vavilovia strains, indicating that V. formosa coexists with ancestral microsymbionts, which are presumably close to the LCA of R. leguminosarum bv. viciae.

journal_name

Genes (Basel)

journal_title

Genes

authors

Chirak ER,Kimeklis AK,Karasev ES,Kopat VV,Safronova VI,Belimov AA,Aksenova TS,Kabilov MR,Provorov NA,Andronov EE

doi

10.3390/genes10120990

subject

Has Abstract

pub_date

2019-12-01 00:00:00

issue

issn

2073-4425

pii

genes10120990

journal_volume

pub_type

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Search for Ancestral Features in Genomes of Rhizobium leguminosarum bv. viciae Strains Isolated from the Relict Legume Vavilovia formosa.