Sindbis virus induces the production of a novel class of endogenous siRNAs in Aedes aegypti mosquitoes
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ABSTRACT: We examined the biogenesis of mRNA-derived endogenous short-interfering RNAs (endo-siRNAs) in the disease vector mosquito, Aedes aegypti. Under standard conditions, mRNA-derived endo-siRNAs were produced from the bidirectional transcription of tail-tail overlapping gene pairs. Upon infection with the alphavirus, Sindbis virus (SINV), another class of mRNA-derived endo-siRNAs was observed. Genes producing SINV-induced endo-siRNAs were not enriched for overlapping partners or nearby genes, but were enriched for transcripts with long 3'UTRs. Endo-siRNAs from this class derived uniformly from the entire length of the target transcript, and were found to regulate the transcript levels of the genes from which they were derived. Strand-specific qPCR experiments demonstrated that antisense strands of targeted mRNA genes were produced to exonic, but not intronic regions. Finally, small RNAs mapped to both sense and antisense strands of exon-exon junctions, suggesting double-stranded RNA precursors to SINV-induced endo-siRNAs may be synthesized from mature mRNA templates. These results suggest additional complexity in small RNA pathways and gene regulation in the presence of an infecting virus in disease vector mosquitoes. Examination of endo-siRNA production in Aedes aegypti mosquitoes
Project description:We examined the biogenesis of mRNA-derived endogenous short-interfering RNAs (endo-siRNAs) in the disease vector mosquito, Aedes aegypti. Under standard conditions, mRNA-derived endo-siRNAs were produced from the bidirectional transcription of tail-tail overlapping gene pairs. Upon infection with the alphavirus, Sindbis virus (SINV), another class of mRNA-derived endo-siRNAs was observed. Genes producing SINV-induced endo-siRNAs were not enriched for overlapping partners or nearby genes, but were enriched for transcripts with long 3'UTRs. Endo-siRNAs from this class derived uniformly from the entire length of the target transcript, and were found to regulate the transcript levels of the genes from which they were derived. Strand-specific qPCR experiments demonstrated that antisense strands of targeted mRNA genes were produced to exonic, but not intronic regions. Finally, small RNAs mapped to both sense and antisense strands of exon-exon junctions, suggesting double-stranded RNA precursors to SINV-induced endo-siRNAs may be synthesized from mature mRNA templates. These results suggest additional complexity in small RNA pathways and gene regulation in the presence of an infecting virus in disease vector mosquitoes.
Project description:The impact of global climate change on the transmission dynamics of infectious diseases is the subject of extensive debate. The transmission of mosquito-borne viral diseases is particularly complex, with climatic variables directly affecting many parameters associated with the prevalence of disease vectors. While evidence shows that warmer temperatures often decrease the extrinsic incubation period of an arthropod-borne virus (arbovirus), exposure to cooler temperatures often predisposes disease vector mosquitoes to higher infection rates. RNA interference pathways are essential to antiviral immunity in the mosquito; however, few experiments have explored the effects of temperature on the RNAi machinery. Total small RNAs (miRNAs, siRNAs, piRNAs, etc.) were isolated and sequenced from the heads of sensor strain Aedes aegypti mosquitoes, or from the whole bodies of CHIKV-infected Aedes albopictus mosquitoes 8 hours post infection. Mosquitoes were grown at 18C or 28C in replicates of 1 (Ae. aegypti) or 3 (Ae. albopictus).
Project description:Bacillus thuringiensis israelensis (Bti) toxins are increasingly used for mosquito control, but little is known about the precise mode of action of each of these toxins, and how they interact to kill mosquito larvae. By using RNA sequencing, we investigated change in gene transcription level and polymorphismvariations associatedwith resistance to each Bti Cry toxin and to the full Bti toxin mixture in the dengue vector Aedes aegypti. The upregulation of genes related to chitin metabolismin all selected strain suggests a generalist, non-toxin-specific response to Bti selection in Aedes aegypti. Changes in the transcription level and/or protein sequences of several putative Cry toxin receptors (APNs, ALPs, α-amylases, glucoside hydrolases, ABC transporters) were specific to each Cry toxin. Selective sweeps associated with Cry4Aa resistancewere detected in 2 ALP and 1 APNgenes. The lack of selection of toxin-specific receptors in the Bti-selected strain supports the hypothesis that Cyt toxin acts as a receptor for Cry toxins in mosquitoes.
Project description:The incomplete genome annotation of non-model organisms hampers molecular and proteomic studies. Proteomics informed by transcriptomics (PIT) is suited to non-model organisms because peptides are identified using transcriptomic, not genomic, data. Aedes aegypti is the mosquito vector for the (re-)emerging dengue, chikungunya, yellow fever and Zika viruses. An Ae. aegypti genome sequence is available, however experimental evidence for >90% of the Ae. aegypti proteome or the activity of transposable elements (TEs) that constitute 50% of the Ae. aegypti genome is lacking. We used PIT to characterise the proteome of the Aedes aegypti derived cell line Aag2. Hotspots of incomplete genome annotation were identified which are not explained by poor sequence and assembly quality. We developed criteria for the characterisation of proteomically active TEs and demonstrate that protein expression does not correlate with a TE’s genomic abundance. Finally, we identify Phasi Charoen-like virus as an unrecognised contaminant of Aag2 cells. We therefore present the first proteomic characterisation of mobile genetic elements, and provide proof-of-principle that PIT can evaluate a genome’s annotation to guide annotation efforts.
Project description:Aedes aegypti mosquitoes vector several arboviruses of global health significance, including dengue viruses and chikungunya virus. RNA interference (RNAi) plays an important role in antiviral immunity, gene regulation and protection from transposable elements. Double-stranded RNA binding proteins (dsRBPs) are important for efficient RNAi; in Drosophila functional specialization of the miRNA, endo-siRNA and exo-siRNA pathway is aided by the dsRBPs Loqs-PB, Loqs-PD and R2D2, respectively. However, this functional specialization has not been investigated in other dipterans. Characterization of the gene structure, expression pattern and interactions with other RNAi/miRNA components revealed that mosquito Loqs/R3D1 isoform -PA, but not -PB interacted readily with both AeAGO1 and AeAGO2. This interaction was mapped to a 32 a.a. region predicted to be structurally similar to the unique 22 a.a. tail of Drosophila Loqs-PD. No -PD isoforms could be detected in Ae. aegypti; analysis of other dipteran genomes demonstrated that this isoform is not conserved outside of Drosophila. Overexpression experiments indicated that Loqs/R3D1-PA participates in endo-siRNA, but not exo-siRNA based silencing. We conclude that the functional specialization of Loqs-PD in Drosophila is a recently derived trait, and that in other dipterans, including the medically important mosquitoes, Loqs/R3D1-A participates in both the miRNA and endo-siRNA based pathways. 12 samples, 3 replicates of each type of sample. The GFP sample is the reference sample
Project description:To investigate the repertoire of proteins interacting with the Aedes aegypti TUDOR protein AAEL012437 (Veneno), we transiently expressed a GFP-Veneno transgene in Aag2 cells. These cells were either infected with the alphavirus Sindbis virus (SINV) or mock-infected. Subsequently, cells were lysed and processed for immunoprecipitation using GFP-TRAP beads to purify Veneno-complexes. The same approach was followed for a truncated transgene lacking the first 205 amino acids (C206).
Project description:PIWI-interacting (pi) RNAs are a class of small RNAs that have diverse functions in mosquitoes. In order to uncover novel components involved in biogenesis or function of the piRNA pathway in Aedes aegypti mosquitoes, we performed mass spectrometry analyses on immunoprecipitated PIWI proteins and their interactors.
Project description:Proteomic analysis of Ago2-/- oocytes revealed that Ago2 interacted with endogenous small interfering RNAs (endo-siRNAs) to repress mRNA translation globally.
Project description:The emergence of mosquito-borne diseases because of climate change emphasizes the need to study arbovirus-vector protein-protein interactions (PPI) to better understand viral replication and transmission. One such human pathogenic arbovirus is Zika virus (ZIKV; Flaviviridae), transmitted by Aedes aegypti mosquitoes. With the lack of molecular tools to study mosquito cells, we developed an Ae. aegypti AF5 cell line stably expressing ZIKV capsid to investigate PPI through label-free quantification proteomics. We identified 157 interactors with 8 potentially pro-viral during ZIKV infection and showed that the transitional endoplasmic reticulum 94 (TER94) protein of the ubiquitin-proteasome pathway (UPP) was important during ZIKV infection in mosquito cells. Silencing TER94 in AF5 cells prevented ZIKV capsid degradation and significantly reduced the establishment of replication at the early stages of infection. Human TER94 ortholog, valosin containing protein (VCP), identified through ortholog mapping, was found to have a similar function during ZIKV infection in A549 cells. ZIKV had reduced ability to replicate when ubiquitination and VCP function were blocked by chemical inhibitors. Furthermore, ubiquitin protein ligase E3 component n-recognin 5 (UBR5) was identified as a TER94/VCP co-factor for capsid interaction. Our study demonstrates a conserved function for TER94/VCP-UPP during early ZIKV infection in mosquito and human cells.
Project description:We report the RNA-seq based analyses of the transcriptional changes in the Aedes aegypti transcriptome 5 hours after blood feeding. Comparison of the transcriptome of Aedes aegypti females at two physiological conditions and one time point.