Search results for "RNA virus"
showing 10 items of 149 documents
EXPERIMENTAL EVOLUTION OF AN EMERGING PLANT VIRUS IN HOST GENOTYPES THAT DIFFER IN THEIR SUSCEPTIBILITY TO INFECTION
2014
This study evaluates the extent to which genetic differences among host individuals from the same species condition the evolution of a plant RNA virus. We performed a threefold replicated evolution experiment in which Tobacco etch potyvirus isolate At17b (TEV-At17b), adapted to Arabidopsis thaliana ecotype Ler-0, was serially passaged in five genetically heterogeneous ecotypes of A. thaliana. After 15 passages we found that evolved viruses improved their fitness, showed higher infectivity and stronger virulence in their local host ecotypes. The genome of evolved lineages was sequenced and putative adaptive mutations identified. Host-driven convergent mutations have been identified. Evidence…
A genetic background with low mutational robustness is associated with increased adaptability to a novel host in an RNA virus.
2009
Although mutational robustness is central to many evolutionary processes, its relationship to evolvability remains poorly understood and has been very rarely tested experimentally. Here, we measure the evolvability of Vesicular stomatitis virus in two genetic backgrounds with different levels of mutational robustness. We passaged the viruses into a novel cell type to model a host-jump episode, quantified changes in infectivity and fitness in the new host, evaluated the cost of adaptation in the original host and analyzed the genetic basis of this adaptation. Lineages evolved from the less robust genetic background demonstrated increased adaptability, paid similar costs of adaptation to the …
Little Evidence for Synergism Among Deleterious Mutations in a Nonsegmented RNA Virus
1999
Several models have been proposed to account for the segmentation of RNA viruses. One of the best known models suggests that segmentation, and mixing of segments during coinfections, is a way to eliminate deleterious mutations from the genome. However, for validity, this model requires that deleterious mutations interact in a synergistic way. That is, two mutations together should have a more deleterious effect than the result of adding their individual effects. Here I present evidence that deleterious mutations in foot-and-mouth disease virus produce a decline in fitness but that the relationship between the number of mutations fixed and the magnitude of fitness decline is compatible mainl…
Rapid evolution of translational control mechanisms in RNA genomes
1997
We have introduced 13 base substitutions into the coat protein gene of RNA bacteriophage MS2. The mutations, which are clustered ahead of the overlapping lysis cistron, do not change the amino acid sequence of the coat protein, but they disrupt a local hairpin, which is needed to control translation of the lysis gene. The mutations decreased the phage titer by four orders of magnitude but, upon passaging, the virus accumulated suppressor mutations that raised the fitness to almost wild-type level. Analysis of the pseudorevertants showed that the disruption of the local hairpin, controlling expression of the lysis gene, had apparently been so complete that its restoration by chance mutations…
Innate immune pathways act synergistically to constrain RNA virus evolution in Drosophila melanogaster
2021
AbstractHost-pathogen interactions impose recurrent selective pressures that lead to constant adaptation and counter-adaptation in both competing species. Here, we sought to study this evolutionary arms-race and assessed the impact of the innate immune system on viral population diversity and evolution, using D. melanogaster as model host and its natural pathogen Drosophila C virus (DCV). We first isogenized eight fly genotypes generating animals defective for RNAi, Imd and Toll innate immune pathways and also pathogen sensing and gut renewal pathways. Wild-type or mutant flies were then orally infected and DCV was serially passaged ten times. Viral population diversity was studied after ea…
Clonal Interference and the Evolution of RNA Viruses
1999
In asexual populations, beneficial mutations that occur in different lineages compete with one another. This phenomenon, known as clonal interference, ensures that those beneficial mutations that do achieve fixation are of large effect. Clonal interference also increases the time between fixations, thereby slowing the adaptation of asexual populations. The effects of clonal interference were measured in the asexual RNA virus vesicular stomatitis virus; rates and average effects of beneficial mutations were quantified.
Is group selection a factor modulating the virulence of RNA viruses?
1997
RNA viruses consist of populations of extremely high genetic heterogeneity called quasispecies. Based on theoretical considerations, it has been suggested that the unit of selection in such complex genetic populations is not the single viral particle but a set of genetically related particles which form the quasispecies. In the present study we carried out a set of experiments with the vesicular stomatitis virus (VSV) dealing with the evolution of life-history characters under selection acting at two factors either in the same or in opposite directions. The two factors at which selective pressure is applied are the individual and the group. We show evidence that group selection modulates th…
The evolution of RNA viruses: A population genetics view.
2000
RNA viruses are excellent experimental models for studying evolution under the theoretical framework of population genetics. For a proper justification of this thesis we have introduced some properties of RNA viruses that are relevant for studying evolution. On the other hand, population genetics is a reductionistic theory of evolution. It does not consider or make simplistic assumptions on the transformation laws within and between genotypic and phenotypic spaces. However, such laws are minimized in the case of RNA viruses because the phenotypic space maps onto the genotypic space in a much more linear way than on higher DNA-based organisms. Under experimental conditions, we have tested th…
Prisoner's dilemma in an RNA virus
1999
The evolution of competitive interactions among viruses1 was studied in the RNA phage φ6 at high and low multiplicities of infection (that is, at high and low ratios of infecting phage to host cells). At high multiplicities, many phage infect and reproduce in the same host cell, whereas at low multiplicities the viruses reproduce mainly as clones. An unexpected result of this study1 was that phage grown at high rates of co-infection increased in fitness initially, but then evolved lowered fitness. Here we show that the fitness of the high-multiplicity phage relative to their ancestors generates a pay-off matrix conforming to the prisoner's dilemma strategy of game theory2,3. In this strateg…
Experimental Evolution and Population Genetics of RNA Viruses
2009
Viral studies have contributed substantially to the field of experimental evolution during the last two decades. The rapid evolution of RNA viruses makes them especially suitable for investigating real-time evolution, while their small genomes facilitate the analysis of the genetic basis of evolutionary change. We review recent advances in RNA virus experimental evolution, focusing on genetic properties that differentiate them from DNA-based organisms, such as their high mutation rates, small genome sizes, low genetic robustness, and the predominance of antagonistic epistasis. We argue that these properties can explain many aspects of RNA virus evolution, including rapid evolution, marked f…