Biology subjects

Schroeder, D. C.

Publications and source records attributed to Schroeder, D. C..

3 recordsLinked to original sources

bioRxiv2025

The effect of two distinct viral-enriched inocula on the immune response and chemical cues in honey bee pupae

The combination of Varroa destructor (Varroa) and the viruses it vectors is a major driver of honey bee (Apis mellifera) colony losses. Hygienic behavior and individual immunity enable bees to cope with some pests and parasites. Hygienic response of adult bees is driven by olfactory cues emanating from diseased brood. In this study, we tested the effect of viral inoculation on the chemical profile and immune response of pupae, independently of Varroa. We injected pupae with various doses of an enriched inocula of either a deformed wing virus (DWV) B-A recombinant or Israeli acute paralysis virus (IAPV) and followed their development and survival for five days. At the end of the five-day period, volatile profiles, viral loads, and expression of seven immune genes were assessed. Both IAPV and the DWV loads increased to equivalent high levels irrespective of the initial dose applied. Notably, greater rates of mortality (60% loss) were observed with the highest IAPV dose when compared to the lowest IAPV dose (15% loss). The DWV inoculum, caused limited mortality but nonetheless inhibited pupae development. The IAPV injected pupae showed evidence of a dose dependent DWV amplification from either a DWV variant in the original IAPV inoculum or from an endogenous source of DWV in the pupae themselves. IAPV-injected pupae had lower expression of immune genes than DWV-injected pupae, suggesting IAPV inhibits the pupae immune response. Overall, among the seven tested immune genes six were upregulated with only vago downregulated, suggesting inhibition of the RNAi pathway following infection. Chemical cues of mock and untreated pupae were similar, but notably different from the virus-injected pupae for both inocula. Our findings show that Varroa-independent virus inoculated pupae produce unique virus-specific chemical cues; the ultimate consequence of such a change might lead to virus specific bee behavioral responses. Authors summaryThis study investigated how two major honey bee viruses, Deformed Wing Virus (DWV) and Israeli Acute Paralysis Virus (IAPV), affect pupae independent of the Varroa mite, which typically spreads them. This study was conducted in the laboratory on incubated pupae isolated from the colony and injected with two viral preparations (inocula). We tested the impact after five-days incubation. The results show that both viruses reach high levels in pupae, though IAPV inoculum proved far more deadly (up to 60% mortality) and appeared to suppress the pupaes immune response, possibly even amplifying co-occurring DWV. While less lethal, the DWV inoculum still inhibited normal development. Interestigly, the virus-infected pupae produced distinct, virus-specific chemical cues--unique volatile profiles different from healthy controls. Since adult honey bees use olfactory cues to detect and remove diseased brood (hygienic behavior), these findings suggest that the viruses themselves generate the "scent of sickness," which could trigger colony-wide behavioral responses and offer a vital target for enhancing the bees natural defenses against these major drivers of colony loss. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=110 SRC="FIGDIR/small/683288v1_ufig1.gif" ALT="Figure 1"> View larger version (30K): org.highwire.dtl.DTLVardef@18e6203org.highwire.dtl.DTLVardef@c4b6d5org.highwire.dtl.DTLVardef@bf6499org.highwire.dtl.DTLVardef@165b9d1_HPS_FORMAT_FIGEXP M_FIG C_FIG

pathology↗

bioRxiv2024

Sacbrood viruses and select Lake Sinai virus variants dominated Apis mellifera colonies symptomatic for European foulbrood

European foulbrood (EFB) is a prevalent disease of the European honey bee (Apis mellifera) in the US, which can lead to colony decline and collapse. The bacterial components of EFB are well studied, but the diversity of viral infections within infected colonies has not been explored. Here we use meta-transcriptomics sequencing of 12 honey bee hives, symptomatic (+) and asymptomatic (-) for EFB to explore viral infection associated with the disease. We identified 41 viral genomes, belonging to two families, with a predominant occurrence of 34 genomes observed in colonies with severe EFB. This is in contrast to fewer, and a complete absence of Dicistroviridae genomes, recovered from healthy colonies (7 genomes). Identified viruses included multiple lineages previously reported in honey bees, namely Lake Sinai virus, Deformed wing virus, Sacbrood virus, Black queen cell virus, and Israeli acute paralysis virus. We observed specific Lake Sinai virus clades associated exclusively with EFB+ or EFB-colonies, in addition to EFB-afflicted colonies that exhibited an increase in relative abundance of sacbrood viruses. Multivariant analyses highlighted that a combination of site and EFB disease status influenced RNA virome composition, while EFB status alone didnt significantly impact it, presenting a challenge for comparisons between colonies kept in different yards. These findings contribute to the understanding of viral dynamics in honey bee colonies compromised by EFB and underscore the need for future investigations to consider viral composition when investigating EFB. ImportanceThis study on the viromes of honey bee colonies affected by European foulbrood (EFB) sheds light on the dynamics of viral populations in bee colonies in the context of a prevalent bacterial brood disease. The identification of distinct Lake Sinai virus and Sacbrood virus clades associated with colonies with severe EFB suggests a potential connection between viral composition and disease status, emphasizing the need for further investigation into the role of viruses during EFB infection. The observed increase in sacbrood viruses during EFB infection implies a possible viral dysbiosis, with potential implications for honey bee brood health. These findings contribute valuable insights for apicultural practices, offering a foundation for future research aimed at understanding and mitigating the impact of bacterial and viral infection in commercial honey bee operations and the management of EFB.

molecular biology↗

bioRxiv2023

Structure and replication cycle of a virus infecting climate-modulating alga Emiliania huxleyi

The globally distributed marine alga Emiliania huxleyi produces reflective calcite disks (coccoliths) that increase the albedo of ocean water and thus reduce the heat absorption in the ocean, which cools the Earths climate. The population density of E. huxleyi is restricted by nucleocytoplasmic large DNA viruses, including E. huxleyi virus 201 (EhV-201). Despite the impact of E. huxleyi viruses on the climate, there is limited information about their structure and replication. Here we show that the dsDNA genome inside the EhV-201 virion is protected by an inner membrane, capsid, and outer membrane decorated with numerous transmembrane proteins. The virions are prone to deformation, and parts of their capsids deviate from the icosahedral arrangement. EhV-201 virions infect E. huxleyi by using their fivefold vertex to bind to a host cell and fuse the viruss inner membrane with the plasma membrane. Whereas the replication of EhV-201 probably occurs in the nucleus, virions assemble in the cytoplasm at the surface of endoplasmic reticulum-derived membrane segments. Genome packaging initiates synchronously with the capsid assembly and completes through an aperture in the forming capsid. Upon the completion of genome packaging, the capsids change conformation, which enables them to acquire an outer membrane by budding into intracellular vesicles. EhV-201 infection induces a loss of surface protective layers from E. huxleyi cells, which allows the continuous release of virions by exocytosis. Our results provide insight into how EhVs bypass the surface protective layers of E. huxleyi and exploit the organelles of an infected cell for progeny assembly.

molecular biology↗