Isolation of a natural DNA virus of Drosophila melanogaster, and characterisation of host resistance and immune responses

Palmer, William H.; Medd, Nathan; Beard, Philippa M.; Obbard, Darren J.

doi:10.1371/journal.ppat.1007050

Cited by 55 publications

(61 citation statements)

References 92 publications

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“…Analysis of the transcriptional response to viral infections in vivo is complicated by the fact that (i) cell infections are unsynchronized; (ii) host cells are modified through hijacking of cellular functions by viruses; and (iii) many viruses trigger cell lysis and tissue damage, making it complicated to discern the immune response from the non-specific response to stress. Consequently, the transcriptome of virus-infected flies only provides a blurred image of the induced antiviral response 2, 21, 25, 34, 35, 39 . Identification of an agonist of dSTING bypasses the need for the use of viruses and provides a much clearer picture of the modifications of the drosophila transcriptome associated with induction of antiviral immunity.…”

Section: Discussionmentioning

confidence: 99%

2’3’-cGAMP triggers a STING and NF-κB dependent broad antiviral response in Drosophila

Cai

Holleufer

Simonsen

et al. 2019

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28We recently reported that an orthologue of STING regulates infection by picorna-like 29 viruses in drosophila. In mammals, STING is activated by the cyclic dinucleotide 2'3'-30 cGAMP produced by cGAS, which acts as a receptor for cytosolic DNA. Here, we 31show that injection of flies with 2'3'-cGAMP can induce expression of dSTING-32 regulated genes. Co-injection of 2'3'-cGAMP with a panel of RNA or DNA viruses 33 results in significant reduction of viral replication. This 2'3'-cGAMP-mediated 34 protection is still observed in flies mutant for the genes Atg7 and AGO2, which 35encode key components of the autophagy and small interfering RNA pathways, 36 respectively. By contrast, it is abrogated in flies mutant for the NF-κB transcription 37 factor Relish. Analysis of the transcriptome of 2'3'-cGAMP injected flies reveals a 38 complex pattern of response, with early and late induced genes. Our results reveal 39 that dSTING regulates an NF-κB -dependent antiviral program, which predates the 40 emergence of Interferon Regulatory Factors and interferons in vertebrates. 41 42 43 44 45 46 47 48 49 50 51 52 Introduction 53Insects, like all animals, are plagued by viral infections, which they oppose 54 through their innate immune system. Induction of transcription of antiviral genes upon 55 sensing of infection is a common antiviral response observed across kingdoms. In 56 insects, inducible responses contribute to defense against viruses, together with RNA 57 interference (RNAi) and constitutively expressed restriction factors (reviewed in 1 ). 58Apart from RNAi, these mechanisms are still poorly characterized and appear to be 59 largely virus-specific 2-4 . Combining genetics and transcriptomic analysis, we recently 60 showed that the evolutionarily conserved factor dSTING participates together with the 61 kinase IKKβ and the NF-κB transcription factor Relish in a novel pathway controlling 62 infection by the picorna-like viruses Drosophila C virus (DCV) and Cricket Paralysis 63Virus (CrPV) in the model organism Drosophila melanogaster 5 . 64In mammals, STING is a central component of the mammalian cytosolic DNA 65 sensing pathway, where it acts downstream of the receptor cyclic GMP-AMP 66 synthase (cGAS) 6 . Upon binding DNA, cGAS synthesizes 2'3'-cGAMP, a cyclic 67 dinucleotide (CDN) secondary messenger that binds to and activates STING 7-10 . 68Bacteria also synthesize CDNs such as c-di-AMP, c-di-GMP and 3'3'-cGAMP, which 69 can be sensed by STING (reviewed in 11 ). Upon activation, STING recruits through its 70 C-terminal tail (CTT) region the kinase TBK1, which phosphorylates and activates the 71 transcription factor Interferon Regulatory Factor (IRF) 3 to trigger interferon (IFN) 72 production 12 . STING can also activate NF-κB and autophagy independently from its 73 CTT domain in mammalian cells [13][14][15] . 74The identification of STING in animals devoid of interferons, such as insects, 75 raises the question of the ancestral function of this molecule. Since most 76 invertebrates lack the IRF family of tran...

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Section: Discussionmentioning

confidence: 99%

2’3’-cGAMP triggers a STING and NF-κB dependent broad antiviral response in Drosophila

Cai

Holleufer

Simonsen

et al. 2019

Preprint

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“…In addition to DCV, wMel shows anti-viral protection against Nora virus and Flock House virus (FHV) [8,11], although the major effect of the latter is most likely a reduction in host mortality rather than a reduction in viral load or viral clearance [8,11]. As there is no evidence for the blocking of DNA viruses [8,13], these effects appear to be specific to RNA viruses.…”

Section: Introductionmentioning

confidence: 99%

No detectable effect of Wolbachia w Mel on the prevalence and abundance of the RNA virome of Drosophila melanogaster

et al. 2018

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is an endosymbiotic bacterium that can block viral infections in arthropods, generating interest in its potential to control the spread of mosquito-borne disease. is model organism for infection, and the Mel strain of can improve host survival following viral infection. However, it is unclear whether Mel induces anti-viral blocking against the broader native virome of, or whether the major effect of is a reduction in viral abundance rather than viral clearance. We examined the effect of on viral abundance by comparing the total transcriptome of Mel-positive andMel-negative populations sampled from six locations in Australia. In addition, we examined the impact ofMel on individual flies by obtaining transcriptome data from 20 Mel-positive and 20Mel-negative from the location (Melbourne) with highest density ofMel. These data revealed high viral abundance in both -positive and -negative populations and individuals. Notably, none of the viral species identified, representing RNA viruses from at least nine families/floating genera, showed evidence of protection byMel. Although the viral loads of picorna-like viruses are reduced by Mel under experimental conditions, we observed no such effect here. These data show that can harbour abundant RNA viruses regardless of its status and imply that the interaction between and viruses in nature is more complex than simple blocking.

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“…In the fly, for example, resistance to infection by the sigma virus has long been shown to be influenced by a single locus of large effect, as measured by the binary response of exposed animals to a CO 2 paralysis test (Bangham, Knott, Kim, Young, & Jiggins, 2008;Bangham, Obbard, Kim, Haddrill, & Jiggins, 2007;Cogni et al, 2016;Magwire et al, 2012). Including more diverse phenotypes, however, such as changes in longevity, fecundity or virus titre (and also exploring new pathogens), is beginning to uncover many more minor effect loci (Cogni et al, 2016;Howick & Lazzaro, 2017;Palmer, Medd, Beard, Martins et al, 2014). Thus, the prediction that a host's susceptibility to infection may have a different genetic architecture to other complex traits need not apply to all components of disease, but rather, as shown here, to the very specific step that defines whether or not a pathogen has the ability to infect a host.…”

Section: Discussionmentioning

confidence: 99%

Dissecting the genetic architecture of a stepwise infection process

2019

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How a host fights infection depends on an ordered sequence of steps, beginning with attempts to prevent a pathogen from establishing an infection, through to steps that mitigate a pathogen's control of host resources or minimize the damage caused during infection. Yet empirically characterizing the genetic basis of these steps remains challenging. Although each step is likely to have a unique genetic and environmental signature, and may therefore respond to selection in different ways, events that occur earlier in the infection process can mask or overwhelm the contributions of subsequent steps. In this study, we dissect the genetic architecture of a stepwise infection process using a quantitative trait locus (QTL) mapping approach. We control for variation at the first line of defence against a bacterial pathogen and expose downstream genetic variability related to the host's ability to mitigate the damage pathogens cause. In our model, the water‐flea Daphnia magna, we found a single major effect QTL, explaining 64% of the variance, that is linked to the host's ability to completely block pathogen entry by preventing their attachment to the host oesophagus; this is consistent with the detection of this locus in previous studies. In susceptible hosts allowing attachment, however, a further 23 QTLs, explaining between 5% and 16% of the variance, were mapped to traits related to the expression of disease. The general lack of pleiotropy and epistasis for traits related to the different stages of the infection process, together with the wide distribution of QTLs across the genome, highlights the modular nature of a host's defence portfolio, and the potential for each different step to evolve independently. We discuss how isolating the genetic basis of individual steps can help to resolve discussion over the genetic architecture of host resistance.

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Isolation of a natural DNA virus of Drosophila melanogaster, and characterisation of host resistance and immune responses

Cited by 55 publications

References 92 publications

2’3’-cGAMP triggers a STING and NF-κB dependent broad antiviral response in Drosophila

2’3’-cGAMP triggers a STING and NF-κB dependent broad antiviral response in Drosophila

No detectable effect of Wolbachia w Mel on the prevalence and abundance of the RNA virome of Drosophila melanogaster

Dissecting the genetic architecture of a stepwise infection process

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