scholarly journals Experimental Evolution of Legume Symbionts: What Have We Learnt?

Genes ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 339 ◽  
Author(s):  
Ginaini Grazielli Doin de Moura ◽  
Philippe Remigi ◽  
Catherine Masson-Boivin ◽  
Delphine Capela
Keyword(s):  
Experimental Evolution ◽  
Nitrogen Fixing ◽  
Plant Selection ◽  
Cell Infection ◽  
Symbiotic Gene ◽  
Symbiotic Plasmid ◽  
Evolutionary Scenario ◽  
Gene Acquisition ◽  
Regulatory Circuits ◽  
Horizontal Transfers

Rhizobia, the nitrogen-fixing symbionts of legumes, are polyphyletic bacteria distributed in many alpha- and beta-proteobacterial genera. They likely emerged and diversified through independent horizontal transfers of key symbiotic genes. To replay the evolution of a new rhizobium genus under laboratory conditions, the symbiotic plasmid of Cupriavidus taiwanensis was introduced in the plant pathogen Ralstonia solanacearum, and the generated proto-rhizobium was submitted to repeated inoculations to the C. taiwanensis host, Mimosa pudica L. This experiment validated a two-step evolutionary scenario of key symbiotic gene acquisition followed by genome remodeling under plant selection. Nodulation and nodule cell infection were obtained and optimized mainly via the rewiring of regulatory circuits of the recipient bacterium. Symbiotic adaptation was shown to be accelerated by the activity of a mutagenesis cassette conserved in most rhizobia. Investigating mutated genes led us to identify new components of R. solanacearum virulence and C. taiwanensis symbiosis. Nitrogen fixation was not acquired in our short experiment. However, we showed that post-infection sanctions allowed the increase in frequency of nitrogen-fixing variants among a non-fixing population in the M. pudica–C. taiwanensis system and likely allowed the spread of this trait in natura. Experimental evolution thus provided new insights into rhizobium biology and evolution.

scholarly journals Shaping Bacterial Symbiosis With Legumes by Experimental Evolution

2014 ◽  
Vol 27 (9) ◽  
pp. 956-964 ◽  
Author(s):  
Marta Marchetti ◽  
Alain Jauneau ◽  
Delphine Capela ◽  
Philippe Remigi ◽  
Carine Gris ◽  
...  
Keyword(s):  
Immune Responses ◽  
Experimental Evolution ◽  
Plant Immunity ◽  
Parallel Evolution ◽  
In Planta ◽  
Plant Selection ◽  
Bacterial Symbiosis ◽  
Symbiotic Plasmid ◽  
Nodulation Competitiveness ◽  
Evolution Experiment

Nitrogen-fixing symbionts of legumes have appeared after the emergence of legumes on earth, approximately 70 to 130 million years ago. Since then, symbiotic proficiency has spread to distant genera of α- and β-proteobacteria, via horizontal transfer of essential symbiotic genes and subsequent recipient genome remodeling under plant selection pressure. To tentatively replay rhizobium evolution in laboratory conditions, we previously transferred the symbiotic plasmid of the Mimosa symbiont Cupriavidus taiwanensis in the plant pathogen Ralstonia solanacearum, and selected spontaneous nodulating variants of the chimeric Ralstonia sp. using Mimosa pudica as a trap. Here, we pursued the evolution experiment by submitting two of the rhizobial drafts to serial ex planta–in planta (M. pudica) passages that may mimic alternating of saprophytic and symbiotic lives of rhizobia. Phenotyping 16 cycle-evolved clones showed strong and parallel evolution of several symbiotic traits (i.e., nodulation competitiveness, intracellular infection, and bacteroid persistence). Simultaneously, plant defense reactions decreased within nodules, suggesting that the expression of symbiotic competence requires the capacity to limit plant immunity. Nitrogen fixation was not acquired in the frame of this evolutionarily short experiment, likely due to the still poor persistence of final clones within nodules compared with the reference rhizobium C. taiwanensis. Our results highlight the potential of experimental evolution in improving symbiotic proficiency and for the elucidation of relationship between symbiotic capacities and elicitation of immune responses.

Plasmid replicons of Rhizobium

2005 ◽  
Vol 33 (1) ◽  
pp. 157-158 ◽  
Author(s):  
L.C. Crossman
Keyword(s):  
Short Review ◽  
Nitrogen Fixing ◽  
Rhizobium Etli ◽  
Free Living ◽  
Leguminous Plants ◽  
Symbiotic Plasmid ◽  
Rhizobium Spp ◽  
Plasmid Replicons ◽  
Rhizobium Sp

Rhizobium spp. are found in soil. They are both free-living and found symbiotically associated with the nodules of leguminous plants. Traditionally, studies have focused on the association of these organisms with plants in nitrogen-fixing nodules, since this is regarded as the most important role of these bacteria in the environment. Rhizobium sp. are known to possess several replicons. Some, like the Rhizobium etli symbiotic plasmid p42d and the plasmid pNGR234b of Rhizobium NGR234, have been sequenced and characterized. The plasmids from these organisms are the focus of this short review.

scholarly journals Reconciliation of Gene and Species Trees

2014 ◽  
Vol 2014 ◽  
pp. 1-22 ◽  
Author(s):  
L. Y. Rusin ◽  
E. V. Lyubetskaya ◽  
K. Y. Gorbunov ◽  
V. A. Lyubetsky
Keyword(s):  
Time Scales ◽  
Gene Evolution ◽  
Single Species ◽  
Species Tree ◽  
Gene Duplications ◽  
Species Trees ◽  
Evolutionary Scenario ◽  
Algorithmic Construction ◽  
Basic Ideas ◽  
Horizontal Transfers

The first part of the paper briefly overviews the problem of gene and species trees reconciliation with the focus on defining and algorithmic construction of the evolutionary scenario. Basic ideas are discussed for the aspects of mapping definitions, costs of the mapping and evolutionary scenario, imposing time scales on a scenario, incorporating horizontal gene transfers, binarization and reconciliation of polytomous trees, and construction of species trees and scenarios. The review does not intend to cover the vast diversity of literature published on these subjects. Instead, the authors strived to overview the problem of the evolutionary scenario as a central concept in many areas of evolutionary research. The second part provides detailed mathematical proofs for the solutions of two problems: (i) inferring a gene evolution along a species tree accounting for various types of evolutionary events and (ii) trees reconciliation into a single species tree when only gene duplications and losses are allowed. All proposed algorithms have a cubic time complexity and are mathematically proved to find exact solutions. Solving algorithms for problem (ii) can be naturally extended to incorporate horizontal transfers, other evolutionary events, and time scales on the species tree.

scholarly journals Three Replicons of Rhizobium sp. Strain NGR234 Harbor Symbiotic Gene Sequences

1998 ◽  
Vol 180 (22) ◽  
pp. 6052-6053 ◽  
Author(s):  
Margarita Flores ◽  
Patrick Mavingui ◽  
Lourdes Girard ◽  
Xavier Perret ◽  
William J. Broughton ◽  
...  
Keyword(s):  
Dna Sequences ◽  
Gene Sequences ◽  
Symbiotic Gene ◽  
Symbiotic Plasmid ◽  
Rhizobium Sp

ABSTRACT Rhizobium sp. strain NGR234 contains three replicons: the symbiotic plasmid or pNGR234a, a megaplasmid (pNGR234b), and the chromosome. Symbiotic gene sequences not present in pNGR234a were analyzed by hybridization. DNA sequences homologous to the genes fixLJKNOPQGHIS were found on the chromosome, while sequences homologous to nodPQ andexoBDFLK were found on pNGR234b.

scholarly journals Mutation rate of SARS-CoV-2 and emergence of mutators during experimental evolution

2021 ◽  
Author(s):  
Vitor Borges ◽  
Maria Joao Alves ◽  
Massimo Amicone ◽  
Joana Isidro ◽  
Libia Ze-Ze ◽  
...  
Keyword(s):  
Mutation Rate ◽  
Experimental Evolution ◽  
Evolutionary Biology ◽  
De Novo ◽  
Immune Surveillance ◽  
De Novo Mutations ◽  
Adaptive Potential ◽  
Cell Infection ◽  
High Frequencies ◽  
Spike Gene

"How predictable is evolution?" is a key question in evolutionary biology. Experimental evolution has shown that the evolutionary path of microbes can be extraordinarily reproducible. Here, using experimental evolution in two circulating SARS-CoV-2, we estimate its mutation rate and demonstrate the repeatability of its evolution when facing a new cell type but no immune or drug pressures. We estimate a genomic mutation rate of 3.7x10^-6 nt^-1 cycle^-1 for a lineage of SARS-CoV-2 with the originally described spike protein (CoV-2-D) and of 2.9x10^-6 nt^-1 cycle-1 for a lineage carrying the D614G mutation that has spread worldwide (CoV-2-G). We further show that mutation accumulation is heterogeneous along the genome, with the spike gene accumulating mutations at a mean rate 16x10^-6 nt^-1 per infection cycle across backgrounds, five-fold higher than the genomic average. We observe the emergence of mutators in the CoV-2-G background, likely linked to mutations in the RNA-dependent RNA polymerase and/or in the error-correcting exonuclease protein. Despite strong bottlenecks, several de novo mutations spread to high frequencies by selection and considerable convergent evolution in spike occurs. These results demonstrate the high adaptive potential of SARS-CoV-2 during the first stages of cell infection in the absence of immune surveillance.

The Infection of Cells by Bullet-Shaped Viruses

1969 ◽  
Vol 27 ◽  
pp. 372-373
Author(s):  
Frederick A. Murphy ◽  
Alyne K. Harrison ◽  
Sylvia G. Whitfield
Keyword(s):  
Electron Microscopy ◽  
Physical Properties ◽  
Host Cell ◽  
Thin Section ◽  
Cultured Cells ◽  
Cell Infection ◽  
Thin Section Electron Microscopy ◽  
Section Electron ◽  
Section Electron Microscopy

The bullet-shaped viruses are currently classified together on the basis of similarities in virion morphology and physical properties. Biologically and ecologically the member viruses are extremely diverse. In searching for further bases for making comparisons of these agents, the nature of host cell infection, both in vivo and in cultured cells, has been explored by thin-section electron microscopy.

COVID 19 – Eye Issues

2020 ◽  
Vol 5 (Special) ◽  
Keyword(s):  
Host Cell ◽  
Target Cell ◽  
Cell Receptor ◽  
Human Tissues ◽  
Type Ii ◽  
Cell Infection ◽  
Host Cell Receptor ◽  
Infected Cells ◽  
Cellular Entry

The coronavirus illness (COVID-19) is caused by a new recombinant SARS-CoV (SARS-CoV) virus (SARS-CoV-2). Target cell infection by SARS-CoV is mediated by the prickly protein of the coronavirus and host cell receptor, enzyme 2 converting angiotensin (ACE2) [3]. Similarly, a recent study suggests that cellular entry by SARS-CoV-2 is dependent on both ACE2 as well as type II transmembrane axial protease (TMPRSS2) [4]. This means that detection of ACE2 and PRSS2 expression in human tissues can predict potential infected cells and their respective effects in COVID-19 patients [1].

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