A picorna-like virus from the red imported fire ant, Solenopsis invicta: initial discovery, genome sequence, and characterization

Viral diversity and co-evolutionary dynamics across the ant phylogeny

Knowledge of viral biodiversity within insects, particularly within ants, is extremely limited with only a few environmental viruses from invasive ant species identified to date. This study documents and explores the viral communities in ants. We comprehensively profile the metagenomes of a phylogenetically broad group of 35 ant species with varied ecological traits and report the discovery of 3710 novel and unique ant-associated viral genomes. These previously unknown viruses discovered within this study constitute over 95% of all currently described ant viruses, significantly increasing our knowledge of the ant virosphere. The identified RNA and DNA viruses fill gaps in insect-associated viral phylogenies and uncover evolutionary histories characterized by both frequent host switching and co-divergence. Many ants also host diverse bacterial communities, and we discovered that approximately one-third of these new ant-associated viruses are bacteriophages. Two ecological categories, bacterial abundance in the host and habitat degradation are both correlated with ant viral diversity and help to structure viral communities within ants. These data demonstrate that the ant virosphere is remarkably diverse phylogenetically and genomically and provide a substantial foundation for studies in virus ecology and evolution within eukaryotes. We highlight the importance of studying insect-associated viruses in natural ecosystems in order to more thoroughly and effectively understand host-microbe evolutionary dynamics.

Effect of Solenopsis invicta virus 3 on brood mortality and egg hatch in Solenopsis invicta

Solenopsis invicta virus 3 (SINV-3) has been shown to cause significant mortality among all stages of its host, Solenopsis invicta. One impact of the virus is alteration of worker ant foraging behavior, which results in colony starvation and collapse over time. Additionally, it has been hypothesized that SINV-3 infection of S. invicta may disrupt worker ant brood care behavior. To investigate this possibility, various combinations of SINV-3-infected and -uninfected adult (worker) and immature (brood) stages were placed together and monitored using the response variables, mortality, egg hatch, and virus load. While significant differences in percent cumulative S. invicta worker ant mortality among six combinations of SINV-3-infected and -uninfected stages were observed, no significant differences in percent cumulative mortality of S. invicta larvae or pupae were observed. No significant differences in egg hatch were observed among SINV-3-uninfected, SINV-3-infected (colony-treated and queen-treated), and starved colonies. Eggs hatched normally in 10-12 days for all treatments indicating that egg care by worker ants was unaffected by SINV-3 infection status. The study further clarifies SINV-3 pathogenesis in its host, S. invicta. Larval mortality in SINV-3-infected colonies does not appear to be caused by worker ant neglect. S. invicta brood under the care of SINV-3-infected worker ants did not exhibit higher mortality rates compared with those tended by SINV-3-uninfected worker ants.

Apis mellifera Solinvivirus-1, a Novel Honey Bee Virus That Remained Undetected for over a Decade, Is Widespread in the USA

A metagenomic analysis of the virome of honey bees (Apis mellifera) from an apiary with high rates of unexplained colony losses identified a novel RNA virus. The virus, which was named Apis mellifera solinvivirus 1 (AmSV1), contains a 10.6 kb positive-strand genomic RNA with a single ORF coding for a polyprotein with the protease, helicase, and RNA-dependent RNA polymerase domains, as well as a single jelly-roll structural protein domain, showing highest similarity with viruses in the family Solinviviridae. The injection of honey bee pupae with AmSV1 preparation showed an increase in virus titer and the accumulation of the negative-strand of AmSV1 RNA 3 days after injection, indicating the replication of AmSV1. In the infected worker bees, AmSV1 was present in heads, thoraxes, and abdomens, indicating that this virus causes systemic infection. An analysis of the geographic and historic distribution of AmSV1, using over 900 apiary samples collected across the United States, showed AmSV1 presence since at least 2010. In the year 2021, AmSV1 was detected in 10.45% of apiaries (95%CI: 8.41-12.79%), mostly sampled in June and July in Northwestern and Northeastern United States. The diagnostic methods and information on the AmSV1 distribution will be used to investigate the connection of AmSV1 to honey bee colony losses.

Baseline Analysis of Endophytic Fungal Associates of Solenopsis invicta Buren from Mounds across Five Counties of Guangdong Province, China

Red imported fire ants mounds have been suggested as a potential reservoir for beneficial entomopathogenic fungal species that are vital for more complex roles in the ecosystem aside from infecting the insects. In the current study, the assemblage of fungal symbionts of the red imported fire ants (RIFA) were obtained across five cities in Guangdong Province, China. The sampling areas were selected because of high occurrence of fire ants mounds in the regions. Mound soils, plant debris within mounds, and ants were collected from three sampling locations in each city for potential isolation of entomopathogenic fungal associates of RIFA. All samples were collected during the spring of 2021. Following successful isolation from substrates, the patterns of fungal species composition, and richness were evaluated. In total, 843 isolates were recovered, and based on their phenotypic distinctiveness and molecular characterization based on DNA sequences of multiple loci including the ITS, SSU, and LSU regions, 46 fungal taxa were obtained, including 12 that were unidentified. Species richness and abundance was highest in the mound soils, while the lowest value was recorded from the ant body. As per the different locations, the highest abundance level was recorded in Zhuhai, where 15 fungal taxa were cultivated. The most common taxa across all substrates and locations was Talaromyces diversus. A baseline analysis of the fungal community composition of RIFA would better our understanding on the interactions between these social ants and their associated microbial organisms, and this knowledge in turn would be important for the successful management of the RIFA.

Antiviral immune response reveals host-specific virus infections in natural ant populations

Hosts can carry many viruses in their bodies, but not all of them cause disease. We studied ants as a social host to determine both their overall viral repertoire and the subset of actively infecting viruses across natural populations of three subfamilies: the Argentine ant (Linepithema humile, Dolichoderinae), the invasive garden ant (Lasius neglectus, Formicinae) and the red ant (Myrmica rubra, Myrmicinae). We used a dual sequencing strategy to reconstruct complete virus genomes by RNA-seq and to simultaneously determine the small interfering RNAs (siRNAs) by small RNA sequencing (sRNA-seq), which constitute the host antiviral RNAi immune response. This approach led to the discovery of 41 novel viruses in ants and revealed a host ant-specific RNAi response (21 vs. 22 nt siRNAs) in the different ant species. The efficiency of the RNAi response (sRNA/RNA read count ratio) depended on the virus and the respective ant species, but not its population. Overall, we found the highest virus abundance and diversity per population in Li. humile, followed by La. neglectus and M. rubra. Argentine ants also shared a high proportion of viruses between populations, whilst overlap was nearly absent in M. rubra. Only one of the 59 viruses was found to infect two of the ant species as hosts, revealing high host-specificity in active infections. In contrast, six viruses actively infected one ant species, but were found as contaminants only in the others. Disentangling spillover of disease-causing infection from non-infecting contamination across species is providing relevant information for disease ecology and ecosystem management.

Characterization of Solenopsis invicta virus 4, a polycipivirus infecting the red imported fire ant Solenopsis invicta

Solenopsis invicta virus 4 (SINV-4), a new polycipivirus, was characterized in the host in which it was discovered, Solenopsis invicta. SINV-4 was detected in the worker and larval stages of S. invicta, but not in pupae, male or female alates, or queens. The SINV-4 titer was highest in worker ants, with a mean of 1.14 × 10⁷ ± 5.84 ×10⁷ SINV-4 genome equivalents/ng RNA. Electron microscopic examination of negatively stained samples from particles purified from SINV-4-infected fire ant workers revealed isometric particles with a mean diameter of 47.3 ± 1.4 nm. The mean inter-colony SINV-4 infection rate among S. invicta worker ants was 45.8 ± 38.6 in Alachua County, Florida. In S. invicta collected in Argentina, SINV-4 was detected in 22% of 54 colonies surveyed from across the Formosa region. There did not appear to be any seasonality associated with the SINV-4 infection rate among S. invicta nests. SINV-4 was successfully transmitted to uninfected S. invicta colonies by feeding. Among three colonies of S. invicta inoculated with SINV-4, two retained the infection for up to 72 days. The replicative genome strand of SINV-4 was detected in 18% (n = 11) of SINV-4-infected S. invicta colonies. Among 33 ant species examined, the plus genome strand of SINV-4 was detected in undetermined species of Dorymyrmex and Pheidole, Cyphomyrmex rimosus, Monomorium pharaonis, Pheidole obscurithorax, Solenopsis geminata, Solenopsis richteri, Solenopsis xyloni, and Solenopsis invicta. However, the replicative (minus) genome strand was only detected in S. invicta. SINV-4 infection did not impact brood production or queen fecundity in S. invicta. The mean brood rating (63.3% ± 8.8) after 31 days for SINV-4-infected colonies was not statistically different from that of uninfected colonies (48.3 ± 25.5). At the end of the 31-day test period, mean egg production was not significantly different between SINV-4-infected S. invicta colonies (287.7 ± 45.2 eggs laid/24 hours) and uninfected control colonies (193.0 ± 43.6 eggs laid/24 hours).

Identification of a Novel Solinvivirus with Nuclear Localization Associated with Mass Mortalities in Cultured Whiteleg Shrimp (Penaeus vannamei)

The emergence and spread of disease-causing viruses in shrimp aquaculture is not uncommon. Since 2016, unusual mortalities have been affecting the Brazilian shrimp industry and we have associated these unusual mortalities with a novel variant of infectious myonecrosis virus (IMNV). The transcriptome analysis of these diseased shrimp showed an additional divergent viral sequence that we have assigned to the family Solinviviridae. The novel virus has been tentatively termed Penaeus vannamei solinvivirus (PvSV) (GenBank accession: OP265432). The full-length genome of the PvSV is 10.44 kb (excluding the poly A tail) and codes for a polyprotein of 3326 aa. Five conserved domains coding for a helicase, RdRp, calicivirus coat protein, G-patch and tegument protein were identified. The genome organization of the PvSV is similar to other (Nylan deria fulva virus 1) solinvivirus. A unique feature of this virus that differs from other members of the Solinviviridae is the presence of putative nuclear localization signals. The tissue tropism of this virus is wide, infecting cells of the hepatopancreas, gastrointestinal tract, lymphoid organ and muscle tissue. Another unique feature is that it is the only RNA virus of penaeid shrimp that shows a nuclear localization by in situ hybridization. The PvSV has a wide distribution in Brazil and has been found in the states of Maranhão State (Perizes de Baixo), Piaui State (Mexeriqueira), Ceará State (Camocim, Jaguaruana, Aracati and Alto Santo) and Pará State where it has been detected in coinfections with IMNV. The diagnostic methods developed here (real-time RT-PCR and in situ hybridization) are effective for the detection of the pathogen and should be employed to limit its spread. Furthermore, the identification of the PvSV shows the increasing host range of the relatively new family Solinviviridae.

A new dicistro-like virus from soldier fly, Inopus flavus (Diptera: Stratiomyidae), a pest of sugarcane

Native Australian soldier flies, Inopus spp. (Diptera: Stratiomyidae), are agricultural pests of economic importance to the sugarcane industry. A screen of the salivary gland transcriptome of Inopus flavus (James) revealed the presence of viral RNA belonging to a potentially novel member of the family Dicistroviridae. The complete genome sequence consists of 9793 nucleotides with two open reading frames. The genome includes two potential internal ribosomal entry sites (IRESs): one within the 5' UTR and the other in the intergenic region (IGR). Virus particles purified from infected larvae and visualised by electron microscopy were found to be icosahedral, non-enveloped, and 30 nm in diameter.

Ectoparasitic fungi Rickia wasmannii infection is associated with smaller body size in Myrmica ants

Parasitism-generated negative effects on ant societies are multifaceted, implying individual and colony-level responses. Though laboratory based evidence shows that the sublethal fungus Rickia wasmannii is responsible for physiological and behavioral responses that may negatively affect individual workers' resilience and life expectancy in Myrmica ant workers, colony-level stress response to this parasite is largely unknown. Here, we focus on understanding of a long-term, colony-level effect of Rickia infection on Myrmica scabrinodis ant populations by tracking trait size-based changes. We collected worker specimens from infected and uninfected colonies from the same population in order to: (1) compare body size in response to parasitism, (2) assess the extent to which possible changes in size are associated with the severity of infection, and (3) investigate shifts in body size in response to infection over time by testing correlation of workers' ages and sizes. We found that workers from infected colonies were significantly smaller than their healthy congeners, but neither infection level nor the age of the workers showed significant correlation with the size in infected colonies. Decreasing body sizes in infected colonies can be ascribed to workers' mediated effect toward developing larvae, which are unable to attain the average body size before they pupate.

Ever-increasing viral diversity associated with the red imported fire ant Solenopsis invicta (Formicidae: Hymenoptera)

Background

Advances in sequencing and analysis tools have facilitated discovery of many new viruses from invertebrates, including ants. Solenopsis invicta is an invasive ant that has quickly spread worldwide causing significant ecological and economic impacts. Its virome has begun to be characterized pertaining to potential use of viruses as natural enemies. Although the S. invicta virome is the best characterized among ants, most studies have been performed in its native range, with less information from invaded areas.

Methods

Using a metatranscriptome approach, we further identified and molecularly characterized virus sequences associated with S. invicta, in two introduced areas, U.S and Taiwan. The data set used here was obtained from different stages (larvae, pupa, and adults) of S. invicta life cycle. Publicly available RNA sequences from GenBank’s Sequence Read Archive were downloaded and de novo assembled using CLC Genomics Workbench 20.0.1. Contigs were compared against the non-redundant protein sequences and those showing similarity to viral sequences were further analyzed.

Results

We characterized five putative new viruses associated with S. invicta transcriptomes. Sequence comparisons revealed extensive divergence across ORFs and genomic regions with most of them sharing less than 40% amino acid identity with those closest homologous sequences previously characterized. The first negative-sense single-stranded RNA virus genomic sequences included in the orders Bunyavirales and Mononegavirales are reported. In addition, two positive single-strand virus genome sequences and one single strand DNA virus genome sequence were also identified. While the presence of a putative tenuivirus associated with S. invicta was previously suggested to be a contamination, here we characterized and present strong evidence that Solenopsis invicta virus 14 (SINV-14) is a tenui-like virus that has a long-term association with the ant. Furthermore, based on virus sequence abundance compared to housekeeping genes, phylogenetic relationships, and completeness of viral coding sequences, our results suggest that four of five virus sequences reported, those being SINV-14, SINV-15, SINV-16 and SINV-17, may be associated to viruses actively replicating in the ant S. invicta.

Conclusions

The present study expands our knowledge about viral diversity associated with S. invicta in introduced areas with potential to be used as biological control agents, which will require further biological characterization.

Symbioses among ants and microbes

Ants have been shown to engage in symbiosis across the tree of life, although our knowledge is far from complete. These interactions range from mutualistic to parasitic with several instances of manipulation of host behavior. Nutrient contributions in these symbioses include both farming for food and nitrogen recycling by gut-associated microbes. Interestingly, the ants that are mostly likely to host diverse and likely functional gut microbial communities are those that feed on extreme diets. Although we do see many instances of symbiosis between ants and microbes, there are also examples of species without a functional gut microbiome. Symbiosis among microbes and eukaryotic hosts is common and often considered a hallmark of multicellular evolution [1]. This is true among many of the over 13000 species of ants, although symbiosis between ants and microbes are not ubiquitous. These microbial-ant symbiotic interactions span the tree of life and include microbial eukaryotes, fungi, viruses, and bacteria. These interactions range from pathogenic to mutualistic, with many relationships still not well understood. Although our knowledge of the diversity of these microbes in ants is growing rapidly, and in some cases we know the function and interaction with the host, we still have much to learn about - the little things that run the little things that run the world!

Season- and caste-specific variation in RNA viruses in the invasive Argentine ant European supercolony

The Argentine ant (Linepithema humile, Mayr) is a highly invasive species. Recently, several RNA viruses have been identified in samples from invasive Argentine ant colonies. Using quantitative PCR, we investigated variation in the levels of these viruses in the main European supercolony over the course of a year. We discovered that virus prevalence and amounts of viral RNA were affected by season and caste: ants had more virus types during warm versus cold months, and queens had more virus types and higher virus prevalence than did workers or males. This seasonal variation was largely due to the appearance of positive-strand RNA viruses in the summer and their subsequent disappearance in the winter. The prevalences of positive-strand RNA viruses were positively correlated with worker foraging activity. We hypothesise that during warmer months, ants are more active and more numerous and, as a result, they have more conspecific and heterospecific interactions that promote virus transmission.

The Association between Virus Prevalence and Intercolonial Aggression Levels in the Yellow Crazy Ant, Anoplolepis Gracilipes (Jerdon)

The recent discovery of multiple viruses in ants, along with the widespread infection of their hosts across geographic ranges, provides an excellent opportunity to test whether viral prevalence in the field is associated with the complexity of social interactions in the ant population. In this study, we examined whether the association exists between the field prevalence of a virus and the intercolonial aggression of its ant host, using the yellow crazy ant (Anoplolepis gracilipes) and its natural viral pathogen (TR44839 virus) as a model system. We delimitated the colony boundary and composition of A. gracilipes in a total of 12 study sites in Japan (Okinawa), Taiwan, and Malaysia (Penang), through intercolonial aggression assay. The spatial distribution and prevalence level of the virus was then mapped for each site. The virus occurred at a high prevalence in the surveyed colonies of Okinawa and Taiwan (100% infection rate across all sites), whereas virus prevalence was variable (30%–100%) or none (0%) at the sites in Penang. Coincidentally, colonies in Okinawa and Taiwan displayed a weak intercolonial boundary, as aggression between colonies is generally low or moderate. Contrastingly, sites in Penang were found to harbor a high proportion of mutually aggressive colonies, a pattern potentially indicative of complex colony composition. Our statistical analyses further confirmed the observed correlation, implying that intercolonial interactions likely contribute as one of the effective facilitators of/barriers to virus prevalence in the field population of this ant species.

Different bacterial and viral pathogens trigger distinct immune responses in a globally invasive ant

Invasive species populations periodically collapse from high to low abundance, sometimes even to extinction. Pathogens and the burden they place on invader immune systems have been hypothesised as a mechanism for these collapses. We examined the association of the bacterial pathogen (Pseudomonas spp.) and the viral community with immune gene expression in the globally invasive Argentine ant (Linepithema humile (Mayr)). RNA-seq analysis found evidence for 17 different viruses in Argentine ants from New Zealand, including three bacteriophages with one (Pseudomonas phage PS-1) likely to be attacking the bacterial host. Pathogen loads and prevalence varied immensely. Transcriptomic data showed that immune gene expression was consistent with respect to the viral classification of negative-sense, positive-sense and double-stranded RNA viruses. Genes that were the most strongly associated with the positive-sense RNA viruses such as the Linepithema humile virus 1 (LHUV-1) and the Deformed wing virus (DWV) were peptide recognition proteins assigned to the Toll and Imd pathways. We then used principal components analysis and regression modelling to determine how RT-qPCR derived immune gene expression levels were associated with viral and bacterial loads. Argentine ants mounted a substantial immune response to both Pseudomonas and LHUV-1 infections, involving almost all immune pathways. Other viruses including DWV and the Kashmir bee virus appeared to have much less immunological influence. Different pathogens were associated with varying immunological responses, which we hypothesize to interact with and influence the invasion dynamics of this species.

Nine new RNA viruses associated with the fire ant Solenopsis invicta from its native range

The red imported fire ant (Solenopsis invicta) escaped its natural enemies when it was introduced into North America in the 1930s from South America. US efforts have focused on discovery of natural enemies, like viruses, to provide sustainable control of the ant. Nine new virus genomes were sequenced from the invasive fire ant Solenopsis invicta using metagenomic RNA sequencing. The virus genomes were verified by Sanger sequencing and random amplification of cDNA ends reactions. In addition to the nine new virus genomes, the previously described Solenopsis viruses were also detected, including Solenopsis invicta virus 1 (SINV-1), SINV-2, SINV-3, SINV-4, SINV-5, and Solenopsis invicta densovirus. The virus sequences came from S. invicta workers, larvae, pupae, and dead workers taken from midden piles collected from across the ant's native range in Formosa, Argentina. One of the new virus genomes (Solenopsis invicta virus 6) was also detected in populations of North American S. invicta. Phylogenetic analysis of the RNA dependent RNA polymerase, the entire nonstructural polyprotein, and genome characteristics were used to tentatively taxonomically place these new virus genome sequences; these include four new species of Dicistroviridae, one Polycipiviridae, one Iflaviridae, one Totiviridae, and two genome sequences that were too taxonomically divergent to be placed with certainty. The S. invicta virome is the best characterized from any ant species and includes 13 positive-sense, single-stranded RNA viruses (Solenopsis invicta virus 1 to Solenopsis invicta virus 13), one double-stranded RNA virus (Solenopsis midden virus), and one double-stranded DNA virus (Solenopsis invicta densovirus). These new additions to the S. invicta virome offer potentially new classical biological control agents for S. invicta.

Viral infections in fire ants lead to reduced foraging activity and dietary changes

Despite the presence of conserved innate immune function, many insects have evolved a variety of mechanical, chemical, and behavioral defensive responses to pathogens. Illness-induced anorexia and dietary changes are two behavioral defensive strategies found in some solitary insects, but little is known regarding the role of such behaviors in social insects, especially in ants. In the present study we examined if such reduced foraging activity exists for a social insect, the invasive fire ant Solenopsis invicta, and its viral pathogen, Solenopsis invicta virus 1 (SINV-1). Virus-free fire ant colonies were split into two colony fragments, one of which subsequently was inoculated with SINV-1. Four food resources with different macronutrient ratios were presented to both colony fragments. SINV-1-inoculated colony fragments consistently displayed reduced foraging performance (e.g., foraging intensity and recruitment efficiency), a decline in lipid intake, and a shift in dietary preference to carbohydrate-rich foods compared with virus-free fragments. These findings provide the first evidence for virus-induced behavioral responses and dietary shifts in shaping the host-pathogen interactions in fire ants. The findings also suggest a possible mechanism for how fire ant colonies respond to viral epidemics. Potential implications of these behavioral differences for current management strategies are discussed.

Mortality of Solenopsis invicta Workers (Hymenoptera: Formicidae) After Indirect Exposure to Spores of Three Entomopathogenic Fungi

Mortality caused by indirect exposure to Metarhizium brunneum and Beauveria bassiana (GHA and NI8) to the red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae), workers was evaluated. Groups of 50 workers were placed in one side of dual-box arenas. The opposite side of the arenas was lined with filter paper squares previously sprayed with unformulated purified spores (106 spores/ml) suspended in 0.2% Ethal TDA 3, HLB 8 of the three fungal strains, or untreated filter paper squares as the control. Daily observations were done for 1 wk to determine mortality. Dead ants from each treatment and control were collected, surface cleaned, and placed in PDA media and incubated at 27°C, 60% RH for 7 d to detect fungal growth. The presence of fungal growth in the dead ants confirmed that fungal spores infected workers while walking on the treated paper. In the M. brunneum and B. bassiana GHA treatments, 51.35 and 56.68% of the workers died, respectively, during days 1 and 2. However, only 9.47 and 35.96% of the mortality could be explained by fungal infection by M. brunneum and B. bassiana GHA, respectively. Most of the mortality observed in the B. bassiana NI8 treatment (84.48%) occurred later (between days 4-6) and most of this mortality occurring during day 4 (89.06%) could be explained by B. bassiana infection. Overall mortality was significantly higher in the B. bassiana NI8 treatment than the other two fungi tested and control. Potential application of these fungal strains for fire ant control are discussed.

Prospecting for viral natural enemies of the fire ant Solenopsis invicta in Argentina

Metagenomics and next generation sequencing were employed to discover new virus natural enemies of the fire ant, Solenopsis invicta Buren in its native range (i.e., Formosa, Argentina) with the ultimate goal of testing and releasing new viral pathogens into U.S. S. invicta populations to provide natural, sustainable control of this ant. RNA was purified from worker ants from 182 S. invicta colonies, which was pooled into 4 groups according to location. A library was created from each group and sequenced using Illumina Miseq technology. After a series of winnowing methods to remove S. invicta genes, known S. invicta virus genes, and all other non-virus gene sequences, 61,944 unique singletons were identified with virus identity. These were assembled de novo yielding 171 contiguous sequences with significant identity to non-plant virus genes. Fifteen contiguous sequences exhibited very high expression rates and were detected in all four gene libraries. One contig (Contig_29) exhibited the highest expression level overall and across all four gene libraries. Random amplification of cDNA ends analyses expanded this contiguous sequence yielding a complete virus genome, which we have provisionally named Solenopsis invicta virus 5 (SINV-5). SINV-5 is a positive-sense, single-stranded RNA virus with genome characteristics consistent with insect-infecting viruses from the family Dicistroviridae. Moreover, the replicative genome strand of SINV-5 was detected in worker ants indicating that S. invicta serves as host for the virus. Many additional sequences were identified that are likely of viral origin. These sequences await further investigation to determine their origins and relationship with S. invicta. This study expands knowledge of the RNA virome diversity found within S. invicta populations.

Invertebrate RNA virus diversity from a taxonomic point of view

Invertebrates are hosts to diverse RNA viruses that have all possible types of encapsidated genomes (positive, negative and ambisense single stranded RNA genomes, or a double stranded RNA genome). These viruses also differ markedly in virion morphology and genome structure. Invertebrate RNA viruses are present in three out of four currently recognized orders of RNA viruses: Mononegavirales, Nidovirales, and Picornavirales, and 10 out of 37 RNA virus families that have yet to be assigned to an order. This mini-review describes general properties of the taxonomic groups, which include invertebrate RNA viruses on the basis of their current classification by the International Committee on Taxonomy of Viruses (ICTV).

Single-stranded RNA viruses infecting the invasive Argentine ant, Linepithema humile

Social insects host a diversity of viruses. We examined New Zealand populations of the globally widely distributed invasive Argentine ant (Linepithema humile) for RNA viruses. We used metatranscriptomic analysis, which identified six potential novel viruses in the Dicistroviridae family. Of these, three contigs were confirmed by Sanger sequencing as Linepithema humile virus-1 (LHUV-1), a novel strain of Kashmir bee virus (KBV) and Black queen cell virus (BQCV), while the others were chimeric or misassembled sequences. We extended the known sequence of LHUV-1 to confirm its placement in the Dicistroviridae and categorised its relationship to closest relatives, which were all viruses infecting Hymenoptera. We examined further for known viruses by mapping our metatranscriptomic sequences to all viral genomes, and confirmed KBV, BQCV, LHUV-1 and Deformed wing virus (DWV) presence using qRT-PCR. Viral replication was confirmed for DWV, KBV and LHUV-1. Viral titers in ants were higher in the presence of honey bee hives. Argentine ants appear to host a range of' honey bee' pathogens in addition to a virus currently described only from this invasive ant. The role of these viruses in the population dynamics of the ant remain to be determined, but offer potential targets for biocontrol approaches.

Draft Genome Sequences of Six Novel Picorna-Like Viruses from Washington State Spiders

We report draft genome sequences of six novel Picornavirales members from six different spider species found in Washington state. These six viral sequences distinctly clustered together phylogenetically with less than 35% amino acid identity to the closest reference viral genome.

Virion Structure of Black Queen Cell Virus, a Common Honeybee Pathogen

Viral diseases are a major threat to honeybee (Apis mellifera) populations worldwide and therefore an important factor in reliable crop pollination and food security. Black queen cell virus (BQCV) is the etiological agent of a fatal disease of honeybee queen larvae and pupae. The virus belongs to the genus Triatovirus from the family Dicistroviridae, which is part of the order Picornavirales. Here we present a crystal structure of BQCV determined to a resolution of 3.4 Å. The virion is formed by 60 copies of each of the major capsid proteins VP1, VP2, and VP3; however, there is no density corresponding to a 75-residue-long minor capsid protein VP4 encoded by the BQCV genome. We show that the VP4 subunits are present in the crystallized virions that are infectious. This aspect of the BQCV virion is similar to that of the previously characterized triatoma virus and supports the recent establishment of the separate genus Triatovirus within the family Dicistroviridae. The C terminus of VP1 and CD loops of capsid proteins VP1 and VP3 of BQCV form 34-Å-tall finger-like protrusions at the virion surface. The protrusions are larger than those of related dicistroviruses.

IMPORTANCE The western honeybee is the most important pollinator of all, and it is required to sustain the agricultural production and biodiversity of wild flowering plants. However, honeybee populations worldwide are suffering from virus infections that cause colony losses. One of the most common, and least known, honeybee pathogens is black queen cell virus (BQCV), which at high titers causes queen larvae and pupae to turn black and die. Here we present the three-dimensional virion structure of BQCV, determined by X-ray crystallography. The structure of BQCV reveals large protrusions on the virion surface. Capsid protein VP1 of BQCV does not contain a hydrophobic pocket. Therefore, the BQCV virion structure provides evidence that capsid-binding antiviral compounds that can prevent the replication of vertebrate picornaviruses may be ineffective against honeybee virus infections.

Dose response of red imported fire ant colonies to Solenopsis invicta virus 3

Baiting tests were conducted to evaluate the effect of increasing Solenopsis invicta virus 3 (SINV-3) dose on fire ant colonies. Actively growing early-stage fire ant (Solenopsis invicta Buren) laboratory colonies were pulse-exposed for 24 hours to six concentrations of SINV-3 (10(1), 10(3), 10(5), 10(7), 10(9) genome equivalents/μl) in 1 ml of a 10 % sucrose bait and monitored regularly for two months. SINV-3 concentration had a significant effect on colony health. Brood rating (proportion of brood to worker ants) began to depart from the control group at 19 days for the 10(9) concentration and 26 days for the 10(7) concentration. At 60 days, brood rating was significantly lower among colonies treated with 10(9), 10(7), and 10(5) SINV-3 concentrations. The intermediate concentration, 10(5), appeared to cause a chronic, low-level infection with one colony (n = 9) supporting virus replication. Newly synthesized virus was not detected in any fire ant colonies treated at the 10(1) concentration, indicating that active infections failed to be established at this level of exposure. The highest bait concentration chosen, 10(9), appeared most effective from a control aspect; mean colony brood rating at this concentration (1.1 ± 0.9 at the 60 day time point) indicated poor colony health with minimal brood production. No clear relationship was observed between the quantity of plus genome strand detected and brood rating. Conversely, there was a strong relationship between the presence of the replicative genome strand and declining brood rating, which may serve as a predictor of disease severity. Recommendations for field treatment levels to control fire ants with SINV-3 are discussed.

Draft Genome Sequence of Laverivirus UC1, a Dicistrovirus-Like RNA Virus Featuring an Unusual Genome Organization

We report the draft genome sequence of Laverivirus UC1, assembled from San Francisco wastewater. This dicistronic RNA virus bears some similarity to dicistroviruses; however, it appears to have a unique genome organization relative to all other known RNA viruses.

Bacterial community survey of Solenopsis invicta Buren (red imported fire ant) colonies in the presence and absence of Solenopsis invicta virus (SINV)

Insect bacterial symbionts contribute to many essential biological functions of their hosts and can also influence host fecundity and fitness. The physiological contribution symbionts provide can aid in immune response and xenobiotic detoxification. Both of these immune factors can directly impact strategies aimed at managing insect populations. One biological control strategy that shows promise in insects is the use of single-stranded RNA viruses within the group Dicistroviridae. The Solenopsis invicta Virus (SINV; Dicistroviridae), a ssRNA virus, has been proposed as a potential biological control agent for the urban pest S. invicta Buren or red imported fire ant (RIFA). SINV has been shown to be prevalent in RIFA populations of Texas and Florida; however, mortality is associated with high viral load. In other insect microbe systems, presence of particular bacteria induced resistance against Dicistrovirus. If this type of relationship is present in the RIFA-SINV system, their bacterial community could reduce the effectiveness of SINV as a biological control system. The advantage of 454 pyro-sequencing is that it enables classification of unculturable bacteria. This study examines the bacterial community in brood, workers, and reproductive cast members from colonies with and without SINV infection. Manipulation of the bacterial community may alter virus infection and replication within the mid-gut. Understanding the differences in the microbial community of ant colonies may provide insights that will refine current efforts designing control strategies for this important urban pest.

A metatranscriptomic approach to the identification of microbiota associated with the ant Formica exsecta

Social insects live in cooperative colonies, often in high densities and with closely related individuals, and interact using social contact behaviours. Compared to solitary insects, social insects have evolved multi-level immunity that includes immune responses common to holometabolous insects, and social immunity, which is exclusive to social taxa. This suggests that social insects may be subject to high pathogen pressure, yet relatively little is known about the range of symbiotic and pathogenic microbial communities that associate with social insects. In this study we examined transcriptome data generated from the ant Formica exsecta for sequences identifying as microbes (or other organisms potentially of non-ant origin). Sequences showing homology to two viruses and several other potentially or obligate intracellular organisms, such as Wolbachia, Arsenophonus, Entomoplasmatales and Microsporidia, were present in the transcriptome data. These homologous sequence matches correspond to genera/species that have previously been associated with a variety of insects, including social insects. There were also sequences with identity to several other microbes such as common moulds and soil bacteria. We conclude that this sequence data provides a starting point for a deeper understanding of the biological interactions between a species of ant and the micro- and macrobiotic communities that it potentially encounters.

Geographic distribution suggests that Solenopsis invicta is the host of predilection for Solenopsis invicta virus 1

Solenopsis invicta virus 1 (SINV-1) was found regularly and prevalently in S. invicta. In sampled locations where S. invicta and S. geminata are sympatric (specifically, Gainesville, FL and Travis, TX), SINV-1 was detected in S. geminata. Conversely, in areas in which S. geminata and S. invicta are allopatric, SINV-1 was not detected in S. geminata; these locations included north Australia (n=12), southern Mexico (n=107), Hawaii (n=48), Taiwan (n=12), and the Johnston Atoll (n=6). A similar relationship was observed for S. richteri. In areas in which S. invicta and S. richteri were sympatric, SINV-1 was detected in the S. richteri population, but in areas in which S. invicta and S. richteri were allopatric, SINV-1 was not detected. These occurrences suggest that S. invicta is the host of predilection, or preferred host for SINV-1, and that the congenerics, S. geminata and S. richteri serve as either accidental, reservoir, or transfer hosts. The minus genome strand of SINV-1 was detected in S. geminata and S. richteri indicating that these species may serve as functional hosts capable of supporting SINV-1 replication. SINV-1 was not detected in S. xyloni regardless of its proximity to S. invicta. These results suggest that SINV-1 may be an example of pathogen spillover or pollution.

Host specificity and colony impacts of the fire ant pathogen, Solenopsis invicta virus 3

An understanding of host specificity is essential before pathogens can be used as biopesticides or self-sustaining biocontrol agents. In order to define the host range of the recently discovered Solenopsis invicta virus 3 (SINV-3), we exposed laboratory colonies of 19 species of ants in 14 genera and 4 subfamilies to this virus. Despite extreme exposure during these tests, active, replicating infections only occurred in Solenopsis invicta Buren and hybrid (S. invicta×S. richteri) fire ant colonies. The lack of infections in test Solenopsis geminata fire ants from the United States indicates that SINV-3 is restricted to the saevissima complex of South American fire ants, especially since replicating virus was also found in several field-collected samples of the black imported fire ant, Solenopsis richteri Forel. S. invicta colonies infected with SINV-3 declined dramatically with average brood reductions of 85% or more while colonies of other species exposed to virus remained uninfected and healthy. The combination of high virulence and high host specificity suggest that SINV-3 has the potential for use as either a biopesticide or a self-sustaining biocontrol agent.

Pathogenicity and complete genome sequence analysis of the mud crab dicistrovirus-1

A virus with a particle diameter of approximately 30 nm and no envelope was purified from diseased mud crab, Scylla paramamosain and it was demonstrated to be pathogenic to mud crab. The complete nucleotide sequence analysis indicated that its genome was a single molecule of linear positive-sense ssRNA with a length of 10,415 nucleotides, excluding the 3'poly (A) tail. It consisted of two open reading frames (ORF) separated by an intergenic region (IGR) and flanked by a 5'untranslated region (5'-UTR) and a 3'untranslated region (3'-UTR). The 5'-ORF encode five putative non-structural proteins, including BIR (Baculovirus Inhibitor of Apoptosis Protein Repeat), helicase, VPg (the genome-linked viral protein), 3C-like protease and RdRP (RNA-dependent RNA polymerase), while the 3'-ORF encode the structural protein precursors. This genome organization was consistent with the typical organization of dicistrovirus and the virus was designated as mud crab dicistrovirus-1 (MCDV-1). The results of the phylogenetic analysis of the putative structural protein precursor suggest that MCDV-1 has a closer genetic relationship with Taura syndrome virus (TSV) than do other dicistroviruses and that MCDV-1 is a new member of the family Dicistroviridae and assigned into the genus Aparavirus.

No evidence for translation of pog, a predicted overlapping gene of Solenopsis invicta virus 1

An overlapping open reading frame (ORF) with a potential to encode a functional protein has been identified within the 3'-proximal ORF of Solenopsis invicta virus 1 (SINV-1) and three bee viruses. This ORF has been referred to as predicted overlapping gene (pog). Protein motif searches of POG revealed weak relationships precluding assignment of a potential function. Neither a transcript nor a protein encoded by the pog ORF has been detected. However, recently, a protein encoded by the corresponding +1 overlapping ORF (termed ORFx) in the Israeli acute paralysis virus (IAPV) was demonstrated by recombinant means as well as in IAPV-infected honey bees. The objective of our study was to attempt to provide empirical evidence for the presence of a pog-derived protein from SINV-1-infected fire ants. A number of different laboratory and field SINV-1-infected Solenopsis invicta preparations were examined by western blotting for the presence of a POG protein sequence. In every case, these preparations failed to yield any detectable bands when probed with a polyclonal antibody preparation raised to a portion of the pog predicted protein sequence. Although impossible to prove a negative result, proper controls used in these studies suggested that the pog ORF is not translated into a functional protein in SINV-1.

Metatranscriptomics and pyrosequencing facilitate discovery of potential viral natural enemies of the invasive Caribbean crazy ant, Nylanderia pubens

BACKGROUND

Nylanderia pubens (Forel) is an invasive ant species that in recent years has developed into a serious nuisance problem in the Caribbean and United States. A rapidly expanding range, explosive localized population growth, and control difficulties have elevated this ant to pest status. Professional entomologists and the pest control industry in the United States are urgently trying to understand its biology and develop effective control methods. Currently, no known biological-based control agents are available for use in controlling N. pubens.

METHODOLOGY AND PRINCIPAL FINDINGS

Metagenomics and pyrosequencing techniques were employed to examine the transcriptome of field-collected N. pubens colonies in an effort to identify virus infections with potential to serve as control agents against this pest ant. Pyrosequencing (454-platform) of a non-normalized N. pubens expression library generated 1,306,177 raw sequence reads comprising 450 Mbp. Assembly resulted in generation of 59,017 non-redundant sequences, including 27,348 contigs and 31,669 singlets. BLAST analysis of these non-redundant sequences identified 51 of potential viral origin. Additional analyses winnowed this list of potential viruses to three that appear to replicate in N. pubens.

CONCLUSIONS

Pyrosequencing the transcriptome of field-collected samples of N. pubens has identified at least three sequences that are likely of viral origin and, in which, N. pubens serves as host. In addition, the N. pubens transcriptome provides a genetic resource for the scientific community which is especially important at this early stage of developing a knowledgebase for this new pest.

The complete genome sequence of a single-stranded RNA virus from the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois)

The complete genome sequence of a single-stranded RNA virus infecting the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), was identified by sequencing cDNA prepared from insects collected from the Mississippi Delta. The 9655 nucleotide positive-sense single-stranded RNA genome of the L. lineolaris single-stranded RNA virus (LyLV-1) contained a single open reading frame of 8958 nucleotides encoding a 2986 amino acid genome polypeptide. The open reading frame was flanked by untranslated regions of 603 and 69 nucleotides at the 5'- and 3'- ends of the genome, respectively. Database searches and homology based modeling was used to identify four capsid proteins (VP1-VP4), helicase/AAA-ATPase, cysteine protease (C3P), protease 2A, and the RNA-directed RNA polymerase (RdRp). In addition, a region with weak similarity to the eukaryotic structural maintenance of chromosome (SMC) domain was identified near the amino-terminal of the polyprotein and adjacent to the VP1 domain. The amino acid sequence of LyLV-1 was approximately 44.4% similar to that of sacbrood virus (SBV) of the honey bee. The genomic organization of both viruses showed remarkable similarity with the exception of highly divergent amino acid regions flanking fairly conserved structural and non-structural polypeptide regions. High similarity to the SBV genome and similarities in the genome organization and amino acid sequence with the viruses of the family Iflaviridae suggested that LyLV-1 was a novel member of this family. Virus particles were 39 nm in diameter and appeared to transmit vertically via eggs. Although this virus may only cause covert infections under normal conditions, the potential for using this virus in biological control of L. lineolaris is discussed.

In vivo functional analysis of the Dicistroviridae intergenic region internal ribosome entry sites

Some viral and cellular messages use an alternative mechanism to initiate protein synthesis that involves internal recruitment of the ribosome to an internal ribosome entry site (IRES). The Dicistroviridae intergenic regions (IGR) have been studied as model IRESs to understand the mechanism of IRES-mediated translation. In this study, the in vivo activity of IGR IRESs were compared. Our analysis demonstrates that Class I and II IGR IRESs have comparable translation efficiency in yeast and that Class II is significantly more active in mammalian cells. Furthermore, while Class II IGR IRES activity was enhanced in yeast grown at a higher temperature, temperature did not affect IGR IRES activity in mammalian cells. This suggests that Class II IRESs may not function optimally with yeast ribosomes. Examination of chimeric IGR IRESs, established that the IRES strength and temperature sensitivity are mediated by the ribosome binding domain. In addition, the sequence of the first translated codon is also an important determinant of IRES activity. Our findings provide us with a comprehensive overview of IGR IRES activities and allow us to begin to understand the differences between Classes I and II IGR IRESs.

Examination of host genome for the presence of integrated fragments of Solenopsis invicta virus 1

A series of oligonucleotide primer pairs covering the entire genome of Solenopsis invicta virus 1 (SINV-1) were used to probe the genome of its host, S. invicta, for integrated fragments of the viral genome. All of the oligonucleotide primer sets yielded amplicons of anticipated size from cDNA created from an RNA template from SINV-1. However, no corresponding amplification was observed when genomic DNA (from 32 colonies of S. invicta) was used as template for the PCR amplifications. Host DNA integrity was verified by amplification of an ant-specific gene, SiGSTS1. The representation of fire ant colonies included both social forms, monogyne and polygyne, and those infected and uninfected with SINV-1. Furthermore, no amplification was observed from genomic DNA from ant samples collected from Argentina or the US. Thus, it appears that SINV-1 genome integration, or a portion therein, has not likely occurred within the S. invicta host genome.

Bacterial diversity in Solenopsis invicta and Solenopsis geminata ant colonies characterized by 16S amplicon 454 pyrosequencing

Social insects harbor diverse assemblages of bacterial microbes, which may play a crucial role in the success or failure of biological invasions. The invasive fire ant Solenopsis invicta (Formicidae, Hymenoptera) is a model system for understanding the dynamics of invasive social insects and their biological control. However, little is known about microbes as biotic factors influencing the success or failure of ant invasions. This pilot study is the first attempt to characterize and compare microbial communities associated with the introduced S. invicta and the native Solenopsis geminata in the USA. Using 16S amplicon 454 pyrosequencing, bacterial communities of workers, brood, and soil from nest walls were compared between neighboring S. invicta and S. geminata colonies at Brackenridge Field Laboratory, Austin, Texas, with the aim of identifying potential pathogenic, commensal, or mutualistic microbial associates. Two samples of S. geminata workers showed high counts of Spiroplasma bacteria, a known pathogen or mutualist of other insects. A subsequent analysis using PCR and sequencing confirmed the presence of Spiroplasma in additional colonies of both Solenopsis species. Wolbachia was found in one alate sample of S. geminata, while one brood sample of S. invicta had a high count of Lactococcus. As expected, ant samples from both species showed much lower microbial diversity than the surrounding soil. Both ant species had similar overall bacterial diversities, although little overlap in specific microbes. To properly characterize a single bacterial community associated with a Solenopsis ant sample, rarefaction analyses indicate that it is necessary to obtain 5,000-10,000 sequences. Overall, 16S amplicon 454 pyrosequencing appears to be a cost-effective approach to screen whole microbial diversity associated with invasive ant species.

Interspecific competition between Solenopsis invicta and two native ant species, Pheidole fervens and Monomorium chinense

This study was designed to understand the effects of the interspecific competition between red imported fire ant, Solenopsis invicta Buren and two native ant species, Pheidole fervens Smith and Monomorium chinense Santschi, by conducting colony interference and individual confrontation tests under laboratory conditions. The colony interference test showed that both native ant species, owing to their numerical advantage, killed the Solenopsis invicta virus-1 (SINV-1)-infected or healthy queens of S. invicta. Significantly less time was required for M. chinense to kill all SINV-1-infected S. invicta compared with the time required to kill the healthy S. invicta. Compared with healthy S. invicta, SINV-1-infected S. invicta spent a longer time eliminating the P. fervens colonies. In confrontation tests, M. chinense killed a significantly higher number of infected S. invicta minors than they did healthy minors, but the number of S. invicta majors (either infected or healthy) killed was substantially less. This study found that the viral infection weakened the competitive ability of S. invicta and made them prone to be eliminated by M. chinense but not by P. fervens.

Discovery and effects of Texas Solenopsis invicta virus [SINV-1 (TX5)] on red imported fire ant populations

Solenopsis invicta Buren (Hymenoptera: Formicidae), the red imported fire ant is native to South America but has invaded areas of the southeastern US, and parts of Southern California. The S. invicta virus-1 (SINV-1) is a positive sense, single-stranded RNA picorna-like virus that only affects Solenopsis species. The virus can infect all caste members and developmental stages. Infection of SINV-1 can result in colony collapse in less than 3 months under laboratory conditions. This study screened S. invicta colonies from Texas for the presence of SINV through Reverse Transcriptase PCR (RT-PCR). Positive samples were genetically characterized by direct sequencing and compared with known picorna-like viruses. SINV-1 was detected in ant colonies from Smith and Henderson TX counties. Amino acid sequence comparison of SINV-1 (TX5) ORF2 region showed homologies of 96% with SINV-1, 97% with SINV-1A, 17.6% with SINV-2, and 20.7% with SINV-3. In addition, SINV-1 (TX5) was compared to 18 other Dicistroviridae viruses. Ant-infecting viruses may provide new approaches to suppressing these important economic pests.

Data mining cDNAs reveals three new single stranded RNA viruses in Nasonia (Hymenoptera: Pteromalidae)

We report three novel small RNA viruses uncovered from cDNA libraries from parasitoid wasps in the genus Nasonia. The genome of this kind of virus is a positive-sense single-stranded RNA with a 3' poly(A), which facilitates cloning from cDNAs. Two of the viruses, NvitV-1 and NvitV-2, possess a RNA-dependent RNA polymerase that associates them with the family Iflaviridae of the order Picornavirales. A third virus, NvitV-3, is most similar to the Nora virus from Drosophila. A reverse transcription-PCR method developed for NvitV-1 indicates that it is a persistent commensal infection of Nasonia.

Dicistroviruses

Dicistroviruses are members of a recently defined and rapidly growing family of picornavirus-like RNA viruses called the Dicistroviridae. Dicistroviruses are pathogenic to beneficial arthropods such as honey bees and shrimp and to insect pests of medical and agricultural importance. Our understanding of these viruses is uneven. We present highly advanced studies of the virus particle structure, remarkable mechanisms of internal ribosome entry in translation of viral RNA, and the use of dicistroviruses to study the insect immune system. However, little is known about dicistrovirus RNA replication mechanisms or gene function, except by comparison with picornaviruses. The recent construction of infectious clones of dicistrovirus genomes may fill these gaps in knowledge. We discuss economically important diseases caused by dicistroviruses. Future research may lead to protection of beneficial arthropods from dicistroviruses and to application of dicistroviruses as biopesticides targeting pestiferous insects.

Medium for development of bee cell cultures (Apis mellifera: Hymenoptera: Apidae)

A media for the production of cell cultures from hymenopteran species such as honey bee, Apis mellifera L. (Hymenoptera: Apidae) was developed. Multiple bee cell cultures were produced when using bee larvae and pupae as starting material and modified Hert-Hunter 70 media. Cell culture systems for bees solves an impasse that has hindered efforts to isolate and screen pathogens which may be influencing or causing colony collapse disorder of bees. Multiple life stages of maturing larvae to early pupae were used to successfully establish cell cultures from the tissues of the head, thorax, and abdomen. Multiple cell types were observed which included free-floating suspensions, fibroblast-like, and epithelia-like monolayers. The final culture medium, WH2, was originally developed for hemipterans, Asian citrus psyllid, Diaphorina citri, and leafhopper, Homalodisca vitripennis cell cultures but has been shown to work for a diverse range of insect species such as bees. Bee cell cultures had various doubling times at 21-23 degrees C ranging from 9-15 d. Deformed wing virus was detected in the primary explanted tissues, which tested negative by rt-PCR for Israeli acute paralysis virus (IAPV), Kashmir bee virus, acute bee paralysis virus, and black queen cell virus. Culture inoculation with IAPV from an isolate from Florida field samples, was detectable in cell cultures after two subcultures. Cell culture from hymenoptera species, such as bees, greatly advances the approaches available to the field of study on colony collapse disorders.

The Acute bee paralysis virus-Kashmir bee virus-Israeli acute paralysis virus complex

Acute bee paralysis virus (ABPV), Kashmir bee virus (KBV) and Israeli acute paralysis virus (IAPV) are part of a complex of closely related viruses from the Family Dicistroviridae. These viruses have a widespread prevalence in honey bee (Apis mellifera) colonies and a predominantly sub-clinical etiology that contrasts sharply with the extremely virulent pathology encountered at elevated titres, either artificially induced or encountered naturally. These viruses are frequently implicated in honey bee colony losses, especially when the colonies are infested with the parasitic mite Varroa destructor. Here we review the historical and recent literature of this virus complex, covering history and origins; the geographic, host and tissue distribution; pathology and transmission; genetics and variation; diagnostics, and discuss these within the context of the molecular and biological similarities and differences between the viruses. We also briefly discuss three recent developments relating specifically to IAPV, concerning its association with Colony Collapse Disorder, treatment of IAPV infection with siRNA and possible honey bee resistance to IAPV.

Bioinformatic evidence for a stem-loop structure 5'-adjacent to the IGR-IRES and for an overlapping gene in the bee paralysis dicistroviruses

The family Dicistroviridae (order Picornavirales) includes species that infect insects and other arthropods. These viruses have a linear positive-sense ssRNA genome of ~8-10 kb, which contains two long ORFs. The 5' ORF encodes the nonstructural polyprotein while the 3' ORF encodes the structural polyprotein. The dicistroviruses are noteworthy for the intergenic Internal Ribosome Entry Site (IGR-IRES) that mediates efficient translation initation on the 3' ORF without the requirement for initiator Met-tRNA. Acute bee paralysis virus, Israel acute paralysis virus of bees and Kashmir bee virus form a distinct subgroup within the Dicistroviridae family. In this brief report, we describe the bioinformatic discovery of a new, apparently coding, ORF in these viruses. The ORF overlaps the 5' end of the structural polyprotein coding sequence in the +1 reading frame. We also identify a potential 14-18 bp RNA stem-loop structure 5'-adjacent to the IGR-IRES. We discuss potential translation initiation mechanisms for the novel ORF in the context of the IGR-IRES and 5'-adjacent stem-loop.