Genetic variation affecting host–parasite interactions: major‐effect quantitative trait loci affect the transmission of sigma virus in Drosophila melanogaster (original) (raw)
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One of the major challenges in evolutionary biology is to unravel the genetic basis of adaptation. This issue has been gaining momentum in recent years with the accelerated development of novel genetic and genomic techniques and resources. In this issue of Molecular Ecology, Cogni et al. (2016) address the genetic basis of resistance to two viruses in Drosophila melanogaster using a panel of recombinant inbred lines with unprecedented resolution allowing detection of rare alleles and/or alleles of small effect. The study confirms the role of previously identified genes of major effect and adds novel regions with minor effect to the genetic basis of Drosophila resistance to the Drosophila C virus or the sigma virus. Additional analyses reveal the absence of cross-resistance and of epistasis between the various genomic regions. This detailed information on the genetic architecture of host resistance constitutes an important step towards the understanding of both the physiology of anti...
Heredity, 2003
Variations observed in parasite virulence and host resistance may be the outcome of coevolutionary processes. Recent theoretical developments have led to a 'geographic mosaic theory' of coevolution according to which there are some localities where reciprocal selection occurs (hot spots) and others where it is strongly reduced (cold spots). Studies of host-parasitoid systems back this up, revealing a geographical variation of traits subjected to antagonistic selection governed by variations in the strength of the ecological interactions. A more detailed analysis of the genetic basis of these geographic variations in a model system-the interaction between Drosophila melanogaster and its specific parasitoid Leptopilina boulardi-suggests that cold spots and hot spots are also driven by the amount of genetic variation available for the trait considered. Our approach, based on isolating reference strains, has been found to predict the result of sympatric interactions and it will be helpful in identifying the selective forces responsible for the coevolution. In this model, host resistance to a standardised reference strain is a weak predictor of the outcome of interactions in the field, and the main parameter accounting for the geographic variations is the number of host species available, with less parasitoid virulence towards D. melanogaster being found in areas displaying a more diversified host community.
Psyche: A Journal of Entomology
The immune response of Drosophila melanogaster is complex and involves both specific and general responses to parasites. In this study we tested for cross-immunity for bacteria and viruses by scoring the incidence of infection with the vertically transmitted Sigma virus (DMelSV) in the progeny of a cross between females transmitting DMelSV at high frequencies and males from lines subjected to three selection regimes related to resistance to Bacillus cereus. There was no significant difference in transmission of DMelSV among selection regimes, though results suggest that the B. cereus selected lines had lower rates of infection by DMelSV. We found a significant difference in viral infection with respect to the sex of the progeny, with males consistently less likely to be infected than females. Given a finite energy budget, flies that have experienced immune system challenge may show alterations in other life history traits. Later eclosing progeny were also less likely to be infected ...
Evolution; international journal of organic evolution, 2015
Pathogens exert a strong selective pressure on hosts, entailing host adaptation to infection. This adaptation often affects negatively other fitness-related traits. Such trade-offs may underlie the maintenance of genetic diversity for pathogen resistance. Trade-offs can be tested with experimental evolution of host populations adapting to parasites, using two approaches: (1) measuring changes in immunocompetence in relaxed-selection lines and (2) comparing life-history traits of evolved and control lines in pathogen-free environments. Here, we used both approaches to examine trade-offs in Drosophila melanogaster populations evolving for over 30 generations under infection with Drosophila C Virus or the bacterium Pseudomonas entomophila, the latter through different routes. We find that resistance is maintained after up to 30 generations of relaxed selection. Moreover, no differences in several classical life-history traits between control and evolved populations were found in pathog...
Genetics Selection Evolution, 1989
We investigated genetic variability of traits involved in the successful parasitization of larvae of Drosophila melanogaster and D. simulans by the hymenopteran parasite Leptopilina boulardi. Characters studied were: the rate of infestation, overall developmental success, ability to escape host encapsulation, developmental success after eclosion, and physiological incompatibility between the 2 partners. These investigations were performed over 3 generations (Gl, G2 and G4) using 14 isofemale lines of L. boulardi collected in Tunisia. The host was D. simulans. For the first 4 traits, the mean values were relatively constant from 1 generation to another. Comparisons of variability within and between isofemale lines of the same generation, and correlations between generations, indicate a genetic component for 2 traits: overall developmental success and ability to evade encapsulation. Drosophila parasitoids-host infestationdevelopmental success-encapsulation escape-genetic variability Résumé-Variabilité génétique dans les relations hôte-parasitoïde: utilisation des lignées isofemelles chez un hyménoptère parasite de drosophile. La variabilité génétique de caractères impliqués dans le succès d'infestation de larves de Drosophila melanogaster et de D. simulans par Leptopilina boulardi, un hyménoptère parasite, a été entreprise. Les caractères étudiés étaient: le taux d'infestation, le succès de développement global, l'aptitude à éviter l'encapsulation par l'hôte, le succès de développement après éclosion et l'incompatibilité physiologique entre les 2 partenaires. Cette analyse a été réalisée sur 3 générations (G1, G2 et G4) à partir de 14 lignées isofemelles de L. boulardi originaires de Tunisie. L'hôte utilisé ici, était D. simulans. Les moyennes des 4 premiers caractères restent stables au cours des générations. La comparaison des variabilités intraet interlignées au sein d'une même génération et les corrélations entre les générations révèlent l'existence d'une importante composante génétique pour deux caractères: le succès de développement global et l'aptitude à éviter l'encapsulation. parasites de drosophiles-taux d'infestation-succès de développement-évitement de la réaction de l'hôte-variabilité génétique * Correspondence and reprints.
Genome biology and evolution, 2016
Sigma virus (DMelSV) is ubiquitous in natural populations of Drosophila melanogaster. Host-mediated, selective RNA editing of adenosines to inosines (ADAR) may contribute to control of viral infection by preventing transcripts from being transported into the cytoplasm or being translated accurately; or by increasing the viral genomic mutation rate. Previous PCR-based studies showed that ADAR mutations occur in DMelSV at low frequency. Here we use SOLiD(TM) deep sequencing of flies from a single host population from Athens, GA, USA to comprehensively evaluate patterns of sequence variation in DMelSV with respect to ADAR. GA dinucleotides, which are weak targets of ADAR, are strongly overrepresented in the positive strand of the virus, consistent with selection to generate ADAR resistance on this complement of the transient, double-stranded RNA intermediate in replication and transcription. Potential ADAR sites in a worldwide sample of viruses are more likely to be "resistant&quo...
Drosophila Adaptation to Viral Infection through Defensive Symbiont Evolution
PLOS Genetics, 2016
Microbial symbionts can modulate host interactions with biotic and abiotic factors. Such interactions may affect the evolutionary trajectories of both host and symbiont. Wolbachia protects Drosophila melanogaster against several viral infections and the strength of the protection varies between variants of this endosymbiont. Since Wolbachia is maternally transmitted, its fitness depends on the fitness of its host. Therefore, Wolbachia populations may be under selection when Drosophila is subjected to viral infection. Here we show that in D. melanogaster populations selected for increased survival upon infection with Drosophila C virus there is a strong selection coefficient for specific Wolbachia variants, leading to their fixation. Flies carrying these selected Wolbachia variants have higher survival and fertility upon viral infection when compared to flies with the other variants. These findings demonstrate how the interaction of a host with pathogens shapes the genetic composition of symbiont populations. Furthermore, host adaptation can result from the evolution of its symbionts, with host and symbiont functioning as a single evolutionary unit.