scholarly journals Transposon Extermination Reveals Their Adaptive Fitness Contribution

2021 ◽  
Author(s):  
Susanne Cranz-Mileva ◽  
Eve Reilly ◽  
Noor Chalhoub ◽  
Rohan Patel ◽  
Tania Atanassova ◽  
...  
Keyword(s):  
Natural Selection ◽  
Transposable Elements ◽  
Fission Yeast ◽  
Natural Population ◽  
Copy Number ◽  
Natural Populations ◽  
Metabolic Stress ◽  
Transcriptional Response ◽  
Mitotic Recombination ◽  
Number Dynamics

Transposable Elements are molecular parasites that persist in their host genome by generating new copies to outpace natural selection. Here we measure the parameters governing the copy number dynamics of the fission yeast Tf2 retrotransposons, using experimental and natural populations and a strain where all Tf2 copies are removed. Natural population genomes display active and persistent Tf2 colonies, but in the absence of selection mitotic recombination deletes Tf2 elements at rates that far exceed transposition. We show that Tf2 elements provide a fitness contribution to their host by dynamically rewiring the transcriptional response to metabolic stress. Therefore, Tf2 elements exhibit a mutualistic rather than parasitic behavior toward their host.

scholarly journals GENETIC LOAD IN NATURAL POPULATIONS: IS IT COMPATIBLE WITH THE HYPOTHESIS THAT MANY POLYMORPHISMS ARE MAINTAINED BY NATURAL SELECTION?

Genetics ◽  
1974 ◽  
Vol 77 (3) ◽  
pp. 569-589
Author(s):  
Martin L Tracey ◽  
Francisco J Ayala
Keyword(s):  
Drosophila Melanogaster ◽  
Natural Selection ◽  
Natural Population ◽  
Natural Populations ◽  
Genetic Load ◽  
Structural Genes ◽  
Invertebrate Species ◽  
Average Proportion ◽  
Mean Fitness ◽  
The Mean

ABSTRACT Recent studies of genetically controlled enzyme variation lead to an estimation that at least 30 to 60% of the structural genes are polymorphic in natural populations of many vertebrate and invertebrate species. Some authors have argued that a substantial proportion of these polymorphisms cannot be maintained by natural selection because this would result in an unbearable genetic load. If many polymorphisms are maintained by heterotic natural selection, individuals with much greater than average proportion of homozygous loci should have very low fitness. We have measured in Drosophila melanogaster the fitness of flies homozygous for a complete chromosome relative to normal wild flies. A total of 37 chromosomes from a natural population have been tested using 92 experimental populations. The mean fitness of homozygous flies is 0.12 for second chromosomes, and 0.13 for third chromosomes. These estimates are compatible with the hypothesis that many (more than one thousand) loci are maintained by heterotic selection in natural populations of D. melanogaster.

scholarly journals Three Groups of Transposable Elements with Contrasting Copy Number Dynamics and Host Responses in the Maize (Zea mays ssp. mays) Genome

PLoS Genetics ◽  
2014 ◽  
Vol 10 (4) ◽  
pp. e1004298 ◽  
Author(s):  
Concepcion M. Diez ◽  
Esteban Meca ◽  
Maud I. Tenaillon ◽  
Brandon S. Gaut
Keyword(s):  
Zea Mays ◽  
Transposable Elements ◽  
Copy Number ◽  
Host Responses ◽  
Number Dynamics

On the evolution and population genetics of hybrid-dysgenesis-causing transposable elements in Drosophila

1986 ◽  
Vol 312 (1154) ◽  
pp. 205-215 ◽  
Keyword(s):  
Population Genetics ◽  
Natural Selection ◽  
Transposable Elements ◽  
Transposable Element ◽  
Natural Populations ◽  
Element Composition ◽  
Hybrid Dysgenesis ◽  
Evolutionary Significance ◽  
Genetic Elements ◽  
Transposable Genetic Elements

Much has been learned about transposable genetic elements in Drosophila , but questions still remain, especially concerning their evolutionary significance. Three such questions are considered here, (i) Has the behaviour of transposable elements been most influenced by natural selection at the level of the organism, the population, or the elements themselves? (ii) How did the elements originate in the genome of the species? (iii) Why are laboratory stocks different from natural populations with respect to their transposable element composition? No final answers to these questions are yet available, but by focusing on the two families of hybrid dysgenesis-causing elements, the P and I factors, we can draw some tentative conclusions.

scholarly journals The transposable elements of the Drosophila serrata reference panel

2020 ◽  
Author(s):  
Zachary Tiedeman ◽  
Sarah Signor
Keyword(s):  
Transposable Elements ◽  
Transposable Element ◽  
Copy Number ◽  
Genetic Background ◽  
Natural Populations ◽  
Inbred Lines ◽  
Transposable Element Insertion ◽  
Defense Systems ◽  
Drosophila Serrata ◽  
Transposable Element Copy

AbstractTransposable elements are an important element of the complex genomic ecosystem, proving to be both adaptive and deleterious - repressed by the piRNA system and fixed by selection. Transposable element insertion also appears to be bursty – either due to invasion of new transposable elements that are not yet repressed, de-repression due to instability of organismal defense systems, stress, or genetic variation in hosts. Here, we characterize the transposable element landscape in an important model Drosophila, D. serrata, and investigate variation in transposable element copy number between genotypes and in the population at large. We find that a subset of transposable elements are clearly related to elements annotated in D. melanogaster and D. simulans, suggesting they spread between species more recently than other transposable elements. We also find that transposable elements do proliferate in particular genotypes, and that often if an individual is host to a proliferating transposable element, it is host to more than one proliferating transposable element. In addition, if a transposable element is active in a genotype, it is often active in more than one genotype. This suggests that there is an interaction between the host and the transposable element, such as a permissive genetic background and the presence of potentially active transposable element copies. In natural populations an active transposable element and a permissive background would not be held in association as in inbred lines, suggesting the magnitude of the burst would be much lower. Yet many of the inbred lines have actively proliferating transposable elements suggesting this is an important mechanism by which transposable elements maintain themselves in populations.

scholarly journals Rapid experimental evolution of reproductive isolation from a single natural population

2019 ◽  
Vol 116 (27) ◽  
pp. 13440-13445 ◽  
Author(s):  
Scott M. Villa ◽  
Juan C. Altuna ◽  
James S. Ruff ◽  
Andrew B. Beach ◽  
Lane I. Mulvey ◽  
...  
Keyword(s):  
Body Size ◽  
Natural Selection ◽  
Reproductive Isolation ◽  
Natural Population ◽  
Experimental Evolution ◽  
Natural Populations ◽  
Ecological Speciation ◽  
Phenotypic Trait ◽  
Divergent Natural Selection ◽  
Feather Lice

Ecological speciation occurs when local adaptation generates reproductive isolation as a by-product of natural selection. Although ecological speciation is a fundamental source of diversification, the mechanistic link between natural selection and reproductive isolation remains poorly understood, especially in natural populations. Here, we show that experimental evolution of parasite body size over 4 y (approximately 60 generations) leads to reproductive isolation in natural populations of feather lice on birds. When lice are transferred to pigeons of different sizes, they rapidly evolve differences in body size that are correlated with host size. These differences in size trigger mechanical mating isolation between lice that are locally adapted to the different sized hosts. Size differences among lice also influence the outcome of competition between males for access to females. Thus, body size directly mediates reproductive isolation through its influence on both intersexual compatibility and intrasexual competition. Our results confirm that divergent natural selection acting on a single phenotypic trait can cause reproductive isolation to emerge from a single natural population in real time.

scholarly journals Transposable elements in natural populations of Drosophila melanogaster

2010 ◽  
Vol 365 (1544) ◽  
pp. 1219-1228 ◽  
Author(s):  
Yuh Chwen G. Lee ◽  
Charles H. Langley
Keyword(s):  
Transposable Elements ◽  
Dna Sequences ◽  
Copy Number ◽  
Population Genomics ◽  
Natural Populations ◽  
Crossing Over ◽  
Large Role ◽  
Essential Components ◽  
Replicative Transposition

Transposable elements (TEs) are families of small DNA sequences found in the genomes of virtually all organisms. The sequences typically encode essential components for the replicative transposition sequences of that TE family. Thus, TEs are simply genomic parasites that inflict detrimental mutations on the fitness of their hosts. Several models have been proposed for the containment of TE copy number in outbreeding host populations such as Drosophila . Surveys of the TEs in genomes from natural populations of Drosophila have played a central role in the investigation of TE dynamics. The early surveys indicated that a typical TE insertion is rare in a population, which has been interpreted as evidence that each TE is selected against. The proposed mechanisms of this natural selection are reviewed here. Subsequent and more targeted surveys identify heterogeneity among types of TEs and also highlight the large role of homologous and possibly ectopic crossing over in the dynamics of the Drosophila TEs. The recent discovery of germline-specific RNA interference via the piwi-interacting RNA pathway opens yet another interesting mechanism that may be critical in containing the copy number of TEs in natural populations of Drosophila . The expected flood of Drosophila population genomics is expected to rapidly advance understanding of the dynamics of TEs.

scholarly journals Selection against transposable elements in D. simulans and D. melanogaster

1996 ◽  
Vol 68 (1) ◽  
pp. 9-15 ◽  
Author(s):  
C. Vieira ◽  
C. Biémont
Keyword(s):  
In Situ Hybridization ◽  
Transposable Elements ◽  
Copy Number ◽  
Insertion Site ◽  
Natural Populations ◽  
Lower Proportion ◽  
Major Mechanism ◽  
Insertion Sites ◽  
Copy Number Regulation

SummaryThe insertion site numbers of the transposable elements (TEs) copia, mdgl, 412 and gypsy were determined in various natural populations of Drosophila melanogaster and D. simulans by in situ hybridization. We showed that, while all elements except gypsy had many insertion sites scattered over the chromosomes in D. melanogaster, only the 412 element in D. simulans presented a high number of insertions, and this number was lower than in D. melanogaster. This low 412 site number per genome in D. simulans was associated with a lower proportion of insertions on the X chromosome in comparison with D. melanogaster, as determined in diploid genomes (0·090 for D. simulans against 0·137 for D. melanogaster) and in haploid genomes (0·102 against 0·146), each value being, moreover, lower than the value of 0·20 expected on the hypothesis of no selection against insertional mutations. These results suggest that selection is a major mechanism explaining 412 copy number regulation in Drosophila, and is stronger in D. simulans than in D. melanogaster.

scholarly journals Transposable elements in individual genotypes of Drosophila simulans

2019 ◽  
Author(s):  
Sarah Signor
Keyword(s):  
Transposable Elements ◽  
Transposable Element ◽  
Dna Sequences ◽  
Copy Number ◽  
Natural Populations ◽  
Population Level ◽  
Drosophila Simulans ◽  
Mobile Dna ◽  
Open Question ◽  
Number Of Individuals

AbstractTransposable elements are mobile DNA sequences that are able to copy themselves within a host’s genome. Within insects they often make up a substantial proportion of the genome. While they are the subject of intense research, often times when copy number is estimated it is estimated only at the population level, or in a limited number of individuals within a population. However, an important aspect of transposable element spread is the variance between individuals in activity. Do transposable elements accumulate at different rates in different genetic backgrounds? Using two populations of Drosophila simulans from California and Africa I estimated transposable element copy number in individual genotypes. Some active transposable elements seem to be a property of the species, while others of the populations. I find that in addition to population level differences in transposable element load certain genotypes accumulate transposable elements at a much higher rate than others. Most likely active transposable elements are fairly rare, and were inherited only by specific genotypes that were used to create the inbred lines. Whether or not this reflects dynamics in natural populations, where transposable elements may accumulate in specific genotypes and maintain themselves in the population rather than being active at low levels population wide, is an open question.

scholarly journals The distribution of transposable elements on X chromosomes from a natural population of Drosophila simulans

1995 ◽  
Vol 66 (2) ◽  
pp. 159-166 ◽  
Author(s):  
Sergey V. Nuzhdin
Keyword(s):  
Drosophila Melanogaster ◽  
Transposable Elements ◽  
Transposable Element ◽  
Natural Population ◽  
Copy Number ◽  
Polytene Chromosomes ◽  
Distal Region ◽  
Drosophila Simulans ◽  
Chromosome Band ◽  
X Chromosomes

SummaryThe distribution of 13 transposable element families along 15 X chromosomes from an African natural population of Drosophila simulans was determined by in situ hybridization to polytene chromosomes. The transposable elements cloned from Drosophila melanogaster all hybridized with Drosophila simulans chromosomes. The number of copies per family was 3·5 times lower in the latter species and correlated with the copy number per family in Drosophila melanogaster. With the exception of 297, the copy number per chromosome followed a Poisson distribution. Element frequencies per chromosome band were generally low. However, several sites of the distal region and the base of the X chromosome had high frequencies of occupation. Elements had higher abundance at the base of the chromosome compared to distal regions. Overall, the distribution of transposable elements in Drosophila simulans is similar to that found in Drosophila melanogaster. These data provide evidence for the operation of a force (or forces) opposing transpositional increase in copy number, and that this force is weaker at the bases of chromosomes, consistent with the idea that recombination between elements at non-homologous sites contains TE copy number. The reduction in copy number of all TE families in Drosophila simulans compared to Drosophila melanogaster can be explained by stronger selection against transposable element multiplication and/or lower rates of transposition in Drosophila simulans.

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