scholarly journals The Underlying Structure of Adaptation under Strong Selection in 12 Experimental Yeast Populations

2014 ◽  
Vol 13 (9) ◽  
pp. 1200-1206 ◽  
Author(s):  
Linda M. Kohn ◽  
James B. Anderson
Keyword(s):  
Sexual Reproduction ◽  
Asexual Reproduction ◽  
Experimental Evolution ◽  
Parallel Evolution ◽  
High Salt ◽  
The Other ◽  
Underlying Structure ◽  
Single Nucleotide ◽  
Strong Selection ◽  
Low Glucose

ABSTRACTThe aims of this study were to determine (i) whether adaptation under strong selection occurred through mutations in a narrow target of one or a few nucleotide sites or a broad target of numerous sites and (ii) whether the programs of adaptation previously observed from three experimental populations were unique or shared among populations that underwent parallel evolution. We used archived population samples from a previous study, representing 500 generations of experimental evolution in 12 populations under strong selection, 6 populations in a high-salt environment and 6 populations in a low-glucose environment. Each set of six populations included four with sexual reproduction and two with exclusively asexual reproduction. Populations were sampled as resequenced genomes of 115 individuals and as bulk samples from which frequencies of mutant alleles were estimated. In a high-salt environment, a broad target of 11 mutations within the proton exporter,PMA1, was observed among the six populations, in addition to expansions of theENAgene cluster. This pattern was shared among populations that underwent parallel evolution. In a low-glucose environment, two programs of adaptation were observed. The originally observed pattern of mutation inMDS3/MKT1in population M8 was a narrow target of a single nucleotide, unique to this population. Among the other five populations, the three mutations were shared in a broad target, sensing/signaling genesRAS1andRAS2. RAS1/RAS2mutations were not observed in the high-salt populations;PMA1mutations were observed only in a high-salt environment.

scholarly journals The Advantages of Segregation and the Evolution of Sex

Genetics ◽  
2003 ◽  
Vol 164 (3) ◽  
pp. 1099-1118 ◽  
Author(s):  
Sarah P Otto
Keyword(s):  
Sexual Reproduction ◽  
Asexual Reproduction ◽  
Deleterious Mutations ◽  
Evolution Of Sex ◽  
Beneficial Mutations ◽  
Selection Regime ◽  
Strong Selection ◽  
Genome Wide ◽  
Low Levels

AbstractIn diploids, sexual reproduction promotes both the segregation of alleles at the same locus and the recombination of alleles at different loci. This article is the first to investigate the possibility that sex might have evolved and been maintained to promote segregation, using a model that incorporates both a general selection regime and modifier alleles that alter an individual’s allocation to sexual vs. asexual reproduction. The fate of different modifier alleles was found to depend strongly on the strength of selection at fitness loci and on the presence of inbreeding among individuals undergoing sexual reproduction. When selection is weak and mating occurs randomly among sexually produced gametes, reductions in the occurrence of sex are favored, but the genome-wide strength of selection is extremely small. In contrast, when selection is weak and some inbreeding occurs among gametes, increased allocation to sexual reproduction is expected as long as deleterious mutations are partially recessive and/or beneficial mutations are partially dominant. Under strong selection, the conditions under which increased allocation to sex evolves are reversed. Because deleterious mutations are typically considered to be partially recessive and weakly selected and because most populations exhibit some degree of inbreeding, this model predicts that higher frequencies of sex would evolve and be maintained as a consequence of the effects of segregation. Even with low levels of inbreeding, selection is stronger on a modifier that promotes segregation than on a modifier that promotes recombination, suggesting that the benefits of segregation are more likely than the benefits of recombination to have driven the evolution of sexual reproduction in diploids.

scholarly journals The Medical Triazole Voriconazole Can Select for Tandem Repeat Variations in Azole-Resistant Aspergillus Fumigatus Harboring TR34/L98H Via Asexual Reproduction

2020 ◽  
Vol 6 (4) ◽  
pp. 277
Author(s):  
Jianhua Zhang ◽  
Jan Zoll ◽  
Tobias Engel ◽  
Joost van den Heuvel ◽  
Paul E. Verweij ◽  
...  
Keyword(s):  
Aspergillus Fumigatus ◽  
Asexual Reproduction ◽  
Tandem Repeat ◽  
Experimental Evolution ◽  
High Frequency ◽  
Nucleotide Polymorphisms ◽  
Resistance Mutations ◽  
Single Nucleotide ◽  
Resistant Phenotype ◽  
Selection Of

Azole-resistant Aspergillus fumigatus isolates recovered at high frequency from patients, harbor mutations that are associated with variation of promoter length in the cyp51A gene. Following the discovery of the TR34/L98H genotype, new variations in tandem repeat (TR) length and number of repeats were identified, as well as additional single nucleotide polymorphisms (SNPs) in the cyp51A gene, indicating that the diversity of resistance mutations in A. fumigatus is likely to continue to increase. Investigating the development routes of TR variants is critical to be able to design preventive interventions. In this study, we tested the potential effects of azole exposure on the selection of TR variations, while allowing haploid A. fumigatus to undergo asexual reproduction. Through experimental evolution involving voriconazole (VOR) exposure, an isolate harboring TR343/L98H evolved from a clinical TR34/L98H ancestor isolate, confirmed by whole genome sequencing. TR343/L98H was associated with increased cyp51A expression and high VOR and posaconazole MICs, although additional acquired SNPs could also have contributed to the highly azole-resistant phenotype. Exposure to medical azoles was found to select for TR343, thus supporting the possibility of in-host selection of TR34 variants.

Studies on North Indian Volvocales. VI. On the life cycle and cytology of a new member of Phacotaceae, Dysmorphococcus sarmaii sp. nov.

1981 ◽  
Vol 59 (5) ◽  
pp. 726-734 ◽  
Author(s):  
R. Shyam
Keyword(s):  
New Species ◽  
Life Cycle ◽  
Chromosome Number ◽  
Sexual Reproduction ◽  
Asexual Reproduction ◽  
Morphological Variability ◽  
The Other ◽  
Laboratory Conditions ◽  
Contractile Vacuoles ◽  
A New Species

This paper deals with the morphology, reproduction, and cytology of a new species of Dysmorphococcus, viz., Dysmorphococcus sarmaii sp. nov. (Phacotaceae, Volvocales) from India. The lorica of this flagellate displays a remarkable morphological variability in nature as well as in culture under laboratory conditions. The alga is characterised by an anteriorly bilobed pentagonal lorica ornamentated with polygonal pores, a massive globose chloroplast that lacks a pyrenoid and almost completely occupys the protoplast, a prominent red stigma, two contractile vacuoles located anteriorly near the insertion of the flagella, and flagella that are equal to or a little longer than the length of the lorica. The pentagonal lorica of the present taxon differs remarkably from the broadly ovoid to globose lorica of D. variabilis Takeda, D. coccifer Korschikoff, and D. globosus Bold and Starr. The lorica of D. sarmaii is somewhat comparable in shape to D. punctatus Fott because of its bilobed anterior but differs from the latter in its ornamentation. The massive globose chloroplast lacking a pyrenoid in the present alga differs remarkably from the other species of this genus where the chloroplast possesses one or several pyrenoids. In addition, asexual reproduction, which is accomplished by division of the protoplast within the lorica, results in the production of 8–16 zoospores as compared with the earlier record of 2 and 4 zoospores in this genus. The alga is heterothallic and sexual reproduction, which was not known for the earlier described species of the genus Dysmorphococcus, takes place by isogametes produced 16–32(–64) per cell. The chromosome number recorded for D. sarmaii is n = 10.

scholarly journals Pneumococcal Colonization and Virulence Factors Identified Via Experimental Evolution in Infection Models

2021 ◽  
Author(s):  
Angharad E Green ◽  
Deborah Howarth ◽  
Chrispin Chaguza ◽  
Haley Echlin ◽  
R Frèdi Langendonk ◽  
...  
Keyword(s):  
Experimental Evolution ◽  
Parallel Evolution ◽  
Experimental System ◽  
Serial Passage ◽  
Invasive Disease ◽  
Vaccine Antigen ◽  
Nasopharyngeal Carriage ◽  
Single Nucleotide ◽  
Single Nucleotide Change ◽  
Infection Models

Abstract Streptococcus pneumoniae is a commensal of the human nasopharynx and a major cause of respiratory and invasive disease. We examined adaptation and evolution of pneumococcus, within nasopharynx and lungs, in an experimental system where the selective pressures associated with transmission were removed. This was achieved by serial passage of pneumococci, separately, in mouse models of nasopharyngeal carriage or pneumonia. Passaged pneumococci became more effective colonizers of the respiratory tract and we observed several examples of potential parallel evolution. The cell wall-modifying glycosyltransferase LafA was under strong selection during lung passage, whereas the surface expressed pneumococcal vaccine antigen gene pvaA and the glycerol-3-phosphate dehydrogenase gene gpsA were frequent targets of mutation in nasopharynx-passaged pneumococci. These mutations were not identified in pneumococci that were separately evolved by serial passage on laboratory agar. We focused on gpsA, in which the same single nucleotide polymorphism arose in two independently evolved nasopharynx-passaged lineages. We describe a new role for this gene in nasopharyngeal carriage and show that the identified single nucleotide change confers resistance to oxidative stress and enhanced nasopharyngeal colonization potential. We demonstrate that polymorphisms in gpsA arise and are retained during human colonization. These findings highlight how within-host environmental conditions can determine trajectories of bacterial evolution. Relative invasiveness or attack rate of pneumococcal lineages may be defined by genes that make niche-specific contributions to bacterial fitness. Experimental evolution in animal infection models is a powerful tool to investigate the relative roles played by pathogen virulence and colonization factors within different host niches.

scholarly journals Identification of colonisation and virulence determinants of Streptococcus pneumoniae via experimental evolution in mouse infection models

2020 ◽  
Author(s):  
Angharad E Green ◽  
Deborah Howarth ◽  
Chrispin Chaguza ◽  
Haley Echlin ◽  
R Frèdi Langendonk ◽  
...  
Keyword(s):  
Streptococcus Pneumoniae ◽  
Experimental Evolution ◽  
Parallel Evolution ◽  
Serial Passage ◽  
Invasive Disease ◽  
Virulence Determinants ◽  
Upper Respiratory Tract ◽  
Single Nucleotide ◽  
Single Nucleotide Change ◽  
Infection Models

AbstractStreptococcus pneumoniae is a commensal of the human nasopharynx and a major cause of respiratory and invasive disease. Pneumococcus stimulates upper respiratory tract inflammation that promotes shedding from mucosal surfaces and transmission to new hosts. Colonisation and transmission are partially antagonistic processes. Adhesion to surfaces and evasion of host responses favours the former, whilst detachment, promoted by inflammation, is necessary for the latter. We sought to determine how adaptation and evolution of pneumococcus within its nasopharyngeal niche might progress when selective pressures associated with transmission were removed. This was achieved by serial passage of pneumococci in mouse models of nasopharyngeal carriage, manually transferring bacteria between mice. To assess the role of host environmental factors on pneumococcal evolution, we also performed analogous experimental evolution in a mouse pneumonia model, passaging pneumococci through lungs. Nasopharynx-passaged pneumococci became more effective colonisers, whilst those evolved within lungs showed reduced virulence. We observed selection of mutations in genes associated with cell wall biogenesis and metabolism in both nasopharynx and lung lineages, but identified prominent examples of parallel evolution that were niche specific. We focussed on gpsA, a gene in which the same single nucleotide polymorphism arose in two independently evolved nasopharynx-passaged lineages. We identified a single nucleotide change conferring resistance to oxidative stress and enhanced nasopharyngeal colonisation potential. We show that gpsA is also a frequent target of mutation during human colonisation. These findings highlight the role played by the host environment in determining trajectories of bacterial evolution and the potential of experimental evolution in animal infection models for identification of novel pathogen virulence and colonisation factors.

Gemmae in Tetralophozia setiformis (Anastrophyllaceae, Marchantiophyta) and their second record in Eurasia

2017 ◽  
Vol 51 ◽  
pp. 242-250
Author(s):  
M. V. Dulin
Keyword(s):  
British Columbia ◽  
Asexual Reproduction ◽  
Leaf Shape ◽  
Leaf Size ◽  
Komi Republic ◽  
The Other ◽  
Widespread Species ◽  
Northern Urals ◽  
Sexual And Asexual Reproduction ◽  
Murmansk Region

Tetralophozia setiformis is a widespread species occurring usually without organs of sexual and asexual reproduction. Gemmae of Tetralophozia setiformis were observed for the second time in Russia and Eurasia in the Northern Urals, Komi Republic. They form compact masses over upper leaves. The compact masses consist largely (70 %) of immature gemmae. Description of gemmae and gemmiparous shoots from the Northern Urals and their comparison with those from the other known localities, namely British Columbia (Canada) and the Murmansk Region (European Russia) were carried out. The gemmiparous plants of T. setiformis from the Northern Urals have approximately the same width as plants without gemmae but they are shorter. The leaves of gemmiparous plants from the Northern Urals are similar to leaves of gemmiparous plants from British Columbia. The leaf shape in upper part of the gemmiparous shoots varies from the typical to ± modified from gemmae production. These leaf shape transitions include reduction of leaf size and lobe number from 4 to 2–3, suppression of development and disappearance of characteristic teeth at the base of sinus. Gemmae size (17 × 22 μm) of plants from the Northern Urals is within variability recorded for plants from the Murmansk Region and British Columbia.

Molecular basis of adaptive evolution of sperm motility involved in in vivo fertilization of terrestrial animals

Impact ◽  
2020 ◽  
Vol 2020 (6) ◽  
pp. 73-75
Author(s):  
Akihiko Watanabe
Keyword(s):  
Sexual Reproduction ◽  
Sperm Motility ◽  
Asexual Reproduction ◽  
Acrosome Reaction ◽  
Sperm Morphology ◽  
Adaptive Potential ◽  
Selective Pressures ◽  
The Face ◽  
Genetic Profiles

One of the unifying traits of life on this planet is reproduction, or life's ability to make copies of itself. The mode of reproduction has evolved over time, having almost certainly begun with simple asexual reproduction when the ancestral single celled organism divided into two. Since these beginnings' life has tried out numerous strategies, and perhaps one of the most important and successful has been sexual reproduction. This form of reproduction relies on the union of gametes, otherwise known as sperm and egg. Evolutionarily, sexual reproduction allows for greater adaptive potential because the genes of two unique individuals have a chance to recombine and mix in order to produce a new individual. Unlike asexual reproduction which produces genetically-identical clones of the parent individual, sex produces offspring with novel genes and combinations of genes. Therefore, in the face of new selective pressures there is a higher chance that one of these novel genetic profiles will produce an adaptation that is advantageous in the new circumstances. Dr Akihiko Watanabe is a reproductive biologist based in the Department of Biology, Faculty of Science Yamagata University in Japan, he is currently working on three research projects; a comparative study on the signalling pathways for inducing sperm motility and acrosome reaction in amphibians, the mechanism behind the adaptive modification of sperm morphology and motility, and the origin of sperm motility initiating substance (SMIS).

scholarly journals Cloning of an Avian Adeno-Associated Virus (AAAV) and Generation of Recombinant AAAV Particles

2003 ◽  
Vol 77 (12) ◽  
pp. 6799-6810 ◽  
Author(s):  
Ioannis Bossis ◽  
John A. Chiorini
Keyword(s):  
Nucleotide Substitution ◽  
Amino Acid Level ◽  
The Other ◽  
Transduction Efficiency ◽  
Entire Genome ◽  
Single Nucleotide ◽  
Adeno Associated Virus ◽  
Reading Frame ◽  
Palindromic Structure ◽  
The Relationship

ABSTRACT Recent studies have proposed that adeno-associated viruses (AAVs) are not evolutionarily linked to other mammalian autonomous parvoviruses but are more closely linked to the autonomous parvoviruses of birds. To better understand the relationship between primate and avian AAVs (AAAVs), we cloned and sequenced the genome of an AAAV (ATCC VR-865) and generated recombinant AAAV particles. The genome of AAAV is 4,694 nucleotides in length and has organization similar to that of other AAVs. The entire genome of AAAV displays 56 to 65% identity at the nucleotide level with the other known AAVs. The AAAV genome has inverted terminal repeats of 142 nucleotides, with the first 122 forming the characteristic T-shaped palindromic structure. The putative Rep-binding element consists of a tandem (GAGY)4 repeat, and the putative terminal resolution site (trs), CCGGT/CG, contains a single nucleotide substitution relative to the AAV2 trs. The Rep open reading frame of AAAV displays 50 to 54% identity at the amino acid level with the other AAVs, with most of the diversity clustered at the carboxyl and amino termini. Comparison of the capsid proteins of AAAV and the primate dependoviruses indicate that divergent regions are localized to surface-exposed loops. Despite these sequence differences, we were able to produce recombinant AAAV particles carrying a lacZ reporter gene by cotransfection in 293T cells and were able to examine transduction efficiency in both chicken primary cells and several cell lines. Our findings indicate that AAAV is the most divergent AAV described to date but maintains all the characteristics unique to the genera of dependovirus.

scholarly journals Influence of breeding strategy on genetic diversity of individuals

2021 ◽  
pp. 1168-1174
Author(s):  
A.A. Poroshina ◽  
◽  
D.Yu. Sherbakov ◽  
Keyword(s):  
Genetic Diversity ◽  
Computer Simulation ◽  
Molecular Evolution ◽  
Microsatellite Markers ◽  
Simulation Model ◽  
Sexual Reproduction ◽  
Asexual Reproduction ◽  
Reproductive Strategy ◽  
Breeding Strategy ◽  
Computer Simulation Model

Abstract. Using a computer simulation model, we tried to investigate how the transition from sexual reproduction to asexual reproduction will affect the population of diploid organisms with a neutral character of molecular evolution. At the same time, special attention was paid to the specificity of microsatellite markers. In this paper, we develop fast and inexpensive methods for assessing the changes in populations that occur with a change in reproductive strategy.

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