scholarly journals Leishmania and the Model of Predominant Clonal Evolution

2021 ◽  
Vol 9 (11) ◽  
pp. 2409
Author(s):  
Michel Tibayrenc ◽  
Francisco J. Ayala
Keyword(s):  
High Resolution ◽  
Phylogenetic Signal ◽  
Clonal Evolution ◽  
Natural Populations ◽  
Genetic Exchange ◽  
Pathogenic Microorganisms

As it is the case for other pathogenic microorganisms, the respective impact of clonality and genetic exchange on Leishmania natural populations has been the object of lively debates since the early 1980s. The predominant clonal evolution (PCE) model states that genetic exchange in these parasites’ natural populations may have a high relevance on an evolutionary scale, but is not sufficient to erase a persistent phylogenetic signal and the existence of bifurcating trees. Recent data based on high-resolution markers and genomic polymorphisms fully confirm the PCE model down to a microevolutionary level.

scholarly journals Genomics and High-Resolution Typing Confirm Predominant Clonal Evolution Down to a Microevolutionary Scale in Trypanosoma cruzi

Pathogens ◽  
2020 ◽  
Vol 9 (5) ◽  
pp. 356 ◽  
Author(s):  
Michel Tibayrenc ◽  
Francisco J. Ayala
Keyword(s):  
High Resolution ◽  
Trypanosoma Cruzi ◽  
Chagas Disease ◽  
Genetic Recombination ◽  
Phylogenetic Signal ◽  
Clonal Evolution ◽  
Natural Populations ◽  
Evolutionary Patterns ◽  
The Impact ◽  
Evolutionary Units

Trypanosoma cruzi, the agent of Chagas disease, is a paradigmatic case of the predominant clonal evolution (PCE) model, which states that the impact of genetic recombination in pathogens’ natural populations is not sufficient to suppress a persistent phylogenetic signal at all evolutionary scales. In spite of indications for occasional recombination and meiosis, recent genomics and high-resolution typing data in T. cruzi reject the counterproposal that PCE does not operate at lower evolutionary scales, within the evolutionary units (=near-clades) that subdivide the species. Evolutionary patterns in the agent of Chagas disease at micro- and macroevolutionary scales are strikingly similar (“Russian doll pattern”), suggesting gradual, rather than saltatory evolution.

scholarly journals Reproduction in Trypanosomatids: Past and Present

Biology ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 471
Author(s):  
Camino Gutiérrez-Corbo ◽  
Bárbara Domínguez-Asenjo ◽  
María Martínez-Valladares ◽  
Yolanda Pérez-Pertejo ◽  
Carlos García-Estrada ◽  
...  
Keyword(s):  
Low Income ◽  
Phenotypic Diversity ◽  
Natural Populations ◽  
Genetic Exchange ◽  
Health Concern ◽  
Current Debate ◽  
Naturally Occurring ◽  
Experimental Works ◽  
Genomic Recombination ◽  
The Impact

Diseases caused by trypanosomatids (Sleeping sickness, Chagas disease, and leishmaniasis) are a serious public health concern in low-income endemic countries. These diseases are produced by single-celled parasites with a diploid genome (although aneuploidy is frequent) organized in pairs of non-condensable chromosomes. To explain the way they reproduce through the analysis of natural populations, the theory of strict clonal propagation of these microorganisms was taken as a rule at the beginning of the studies, since it partially justified their genomic stability. However, numerous experimental works provide evidence of sexual reproduction, thus explaining certain naturally occurring events that link the number of meiosis per mitosis and the frequency of mating. Recent techniques have demonstrated genetic exchange between individuals of the same species under laboratory conditions, as well as the expression of meiosis specific genes. The current debate focuses on the frequency of genomic recombination events and its impact on the natural parasite population structure. This paper reviews the results and techniques used to demonstrate the existence of sex in trypanosomatids, the inheritance of kinetoplast DNA (maxi- and minicircles), the impact of genetic exchange in these parasites, and how it can contribute to the phenotypic diversity of natural populations.

scholarly journals Genetic exchange by recombination or reassortment is infrequent in natural populations of a tripartite RNA plant virus.

1997 ◽  
Vol 71 (2) ◽  
pp. 934-940 ◽  
Author(s):  
A Fraile ◽  
J L Alonso-Prados ◽  
M A Aranda ◽  
J J Bernal ◽  
J M Malpica ◽  
...  
Keyword(s):  
Plant Virus ◽  
Natural Populations ◽  
Genetic Exchange

TRIPLOIDY IN NATURAL POPULATIONS OF THE BLACK FLY CNEPHIA MUTATA (MALLOCH)

1959 ◽  
Vol 37 (4) ◽  
pp. 571-589 ◽  
Author(s):  
V. R. Basrur ◽  
K. H. Rothfels
Keyword(s):  
Salivary Gland ◽  
Banding Pattern ◽  
Natural Populations ◽  
Chromosomal Polymorphism ◽  
Genetic Exchange ◽  
Black Flies ◽  
Female Progeny ◽  
Southern Ontario ◽  
Black Fly ◽  
Standard Sequence

Populations of Cnephia mutata in southern Ontario contain both diploid and triploid individuals. The diploid form is bisexual and lacks chromosomal polymorphism except for a rearrangement involved in its cytological sex determining mechanism. The triploids are parthenogenetic; they produce female progeny only and are highly heterozygous for inversions. The banding pattern of the salivary gland chromosomes of diploids and triploids is very similar; the identical standard sequence occurs in both. The complete lack of autosomal inversions in diploids contrasted with their abundance in triploids indicates that effective genetic exchange does not occur between the two forms; they are reproductively completely isolated, although opportunity for cross-mating would seem to exist. The origin of polyploid parthenogenetic forms in black flies is discussed and the view is favored that they are autopolyploid and automictic.

scholarly journals Patterns, predictors, and consequences of dominance in hybrids

2019 ◽  
Author(s):  
Ken A. Thompson ◽  
Mackenzie Urquhart-Cronish ◽  
Kenneth D. Whitney ◽  
Loren H. Rieseberg ◽  
Dolph Schluter
Keyword(s):  
First Generation ◽  
Phylogenetic Signal ◽  
Natural Populations ◽  
The Other ◽  
Common Environment ◽  
Intermediate Phenotypes ◽  
Individual Traits ◽  
General Rules ◽  
Using Data ◽  
Fertile Hybrids

Are first-generation (F1) hybrids typically intermediate for all traits that differentiate their parents? Or are they similar to one parent for most traits, or even mismatched for divergent traits? Although the phenotype of otherwise viable and fertile hybrids determines their fate, little is known about the general patterns, predictors, and consequences of phenotype expression in hybrids. To address this empirical gap, we compiled data from nearly 200 studies where traits were measured in a common environment for two parent populations and F1 hybrids. We find that individual traits are typically halfway between the parental midpoint and one parental value (i.e., hybrid trait values are typically 0.25 or 0.75 if parents’ values are 0 & 1). When considering pairs of traits together, a hybrid’s multivariate phenotype tends to resemble one parent (pairwise parent-bias) about 50 % more than the other while also exhibiting a similar magnitude of trait mismatch due to different traits having dominance in conflicting directions. We detect no phylogenetic signal nor an effect of parental genetic distance on dominance or mismatch. Using data from an experimental field planting of recombinant hybrid sunflowers—where there is among-individual variation in dominance and mismatch due to segregation of divergent alleles—we illustrate that pairwise parent-bias improves fitness while mismatch reduces fitness. Importantly, the effect of mismatch on fitness was stronger than that of pairwise parent-bias. In sum, our study has three major conclusions. First, hybrids between ecologically divergent natural populations are typically not phenotypically intermediate but rather exhibit substantial mismatch while also resembling one parent more than the other. Second, dominance and mismatch are likely determined by population-specific processes rather than general rules. Finally, selection against hybrids likely results from both selection against somewhat intermediate phenotypes and against mismatched trait combinations.

Mixed Infections and Genetic Exchange Occur in Natural Populations of Cucumber Mosaic Cucumovirus

1997 ◽  
pp. 94-99
Author(s):  
Fernando García-Arenal ◽  
José Luis Alonso-Prados ◽  
Miguel A. Aranda ◽  
José M. Malpica ◽  
Aurora Fraile
Keyword(s):  
Natural Populations ◽  
Genetic Exchange ◽  
Mixed Infections ◽  
Cucumber Mosaic Cucumovirus

High Resolution Genome-Wide Analyses Revealed That Bortezomib Selects a Prediagnosis Clone In Relapsed Patients with Multiple Myeloma

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 2960-2960
Author(s):  
Florence Magrangeas ◽  
Hervé Avet-Loiseau ◽  
Olivier Decaux ◽  
Wilfried Gouraud ◽  
jean Luc Harousseau ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
High Resolution ◽  
Copy Number ◽  
Clonal Evolution ◽  
Uniparental Disomy ◽  
Chemotherapeutic Agents ◽  
Advisory Committees ◽  
Bortezomib Treatment ◽  
Genome Wide ◽  
A Minor

Abstract Abstract 2960 Despite advances and significant improvement in survival, multiple myeloma (MM) remains incurable and nearly all patients relapse after treatment. In order to gain insights into the genomic lesions associated with acquisition of drug resistance and progression of disease, we performed high resolution genome-wide single nucleotide polymorphism and copy number analyses on matched diagnostic and relapse samples from 24 MM patients either treated with proteasome inhibitor (bortezomib)-based induction regimen (n=12) or conventional chemotherapeutic agents (n= 12). All relapse samples have a clear relationship to the diagnosis clone. The vast majority of patients (92%) acquired additional copy number abnormalities (CNAs) or uniparental disomy (UPD) at relapse or exhibited change in the pattern of lesions present at diagnosis. Of these, 45% acquired new lesions and 41% both acquired new lesions and lost lesions present at diagnosis. Remarkably, loss of lesions at relapse was significantly associated with initial bortezomib treatment (8 out of 12 versus 1 out of 12; P = 0.009). Moreover, in 75% of the bortezomib-treated MM, the lesions lost at relapse included either UPD or deletion providing direct evidences that the relapse clone arose from a common prediagnosis clone present as a minor population at diagnosis that acquired additional abnormalities before emerging as the relapse clone. These results suggest that resistance to novel therapeutic agent known to target MM cells in the bone marrow milieu preferentially goes through with selection of minor prediagnosis clone while escape to conventional chemotherapeutic agents is almost exclusively associated with clonal evolution from diagnosis clone. These data support the proposal to combine several anti-myeloma drug upfront in order to obtain long-term remissions. Disclosures: Anderson: Millennium Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Munshi:Millennium Pharmaceuticals: Honoraria, Speakers Bureau.

Detection of recurrence and clonal evolution of ANLL-M4 by high resolution banding analysis of the unique reciprocal translocation t(6;9) in a teenager girl

1986 ◽  
Vol 10 (1) ◽  
pp. 107
Author(s):  
N.A. Bëkássy ◽  
S Heim ◽  
U Kristoffersson ◽  
N Mandahl ◽  
F Mitelman ◽  
...  
Keyword(s):  
High Resolution ◽  
Reciprocal Translocation ◽  
Clonal Evolution ◽  
Banding Analysis ◽  
Resolution Banding

The detection of geographical substructuring of Trypanosoma brucei populations by the analysis of minisatellite polymorphisms

Parasitology ◽  
2001 ◽  
Vol 123 (5) ◽  
pp. 475-482 ◽  
Author(s):  
A. MacLEOD ◽  
C. M. R. TURNER ◽  
A. TAIT
Keyword(s):  
Linkage Disequilibrium ◽  
Trypanosoma Brucei ◽  
Natural Populations ◽  
Geographical Location ◽  
Low Frequency ◽  
Genetic Exchange ◽  
Rapid Expansion ◽  
Isolated Populations ◽  
Single Population ◽  
Multilocus Genotypes

Analysis of natural populations of Trypanosoma brucei has shown that there is linkage disequilibrium between alleles at pairs of loci in isolates taken from the field. This disequilibrium can occur as a result of a low frequency of genetic exchange, the masking of frequent genetic exchange by the rapid expansion of a few genotypes or by the treatment of 2 (or more) genetically isolated populations as a single population. We have analysed stocks from 2 geographically separate locations using 3 minisatellite markers to determine the frequencies of the alleles in each area and the frequency and nature of the multilocus genotypes. The results show that many alleles and multilocus genotypes are unique to each geographical location, supporting the conclusion that these populations are genetically isolated with limited or no gene flow between them. This geographical substructuring needs to be taken into account in considering the origins of the linkage disequilibrium in a number of populations.

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