Biology subjects

Norton, A. M.

Publications and source records attributed to Norton, A. M..

3 recordsLinked to original sources

bioRxiv2023

Deformed wing virus genotypes A and B do not elicit immunologically different responses in naive honey bee hosts

Deformed wing virus (DWV), in association with Varroa destructor, is currently the leading factor associated with global honey bee deaths. With the exception of Australia, the virus and mite have a near global distribution, making it difficult to separate the effect of one from the other. Over time, the prevalence of the two main DWV genotypes (DWV-A and DWV-B) has changed, leading to the suggestion that the two strains elicit a different immune response by the host, the western honey bee Apis mellifera. Here we use a honey bee population naive to both the mite and the virus to investigate if honey bees show a different immunological response to DWV genotypes. We examined the expression of 19 immune genes by RT-qPCR and comprehensively analysed the small RNA response in honey bees after experimental injection with DWV-A and DWV-B. We found no evidence to indicate that DWV-A and DWV-B elicit a different immune response in honey bees. We found that RNA interference genes are up-regulated during DWV infection and that the small interfering RNA (siRNA) response is proportional to viral loads, yet does not inhibit the virus from accumulating to high loads. We also found that the siRNA response towards DWV was weaker than the response to another honey bee pathogen, Black queen cell virus. This suggests that DWV is comparatively better at evading antiviral host defences. There was no evidence for the production of virus-derived PIWI-RNAs in response to DWV infection. In contrast to previous studies, and in the absence of V. destructor, we found no evidence that DWV has an immunosuppressive effect in honey bees. Overall, our results advance our understanding of the immunological effect DWV elicits in honey bees.

immunology↗

bioRxiv2023

Virus replication in the honey bee parasite, Varroa destructor

Arthropod vectors such as mites and ticks introduce an alternative viral transmission route between their hosts. The ectoparasitic mite Varroa destructor is the leading threat to the health of Western honey bees (Apis mellifera) primarily through its action as a vector of viruses. However, it is unclear whether viruses transmitted by V. destructor actively infect and replicate in mites, which could facilitate increased transmission and select for more virulent strains. To better understand the role of V. destructor as a vector, we took advantage of differences between bee and mite antiviral RNA interference pathways to identify the host specificity of replicating viruses. We used small RNA sequencing of individual V. destructor mites to examine viral small interfering RNA (vsiRNA) profiles of Deformed wing virus genotypes (DWV-A and DWV-B), associated with colony declines, as well as nine other viruses present in our samples. We found active replication of six V. destructor-associated viruses, including a novel virus, Varroa destructor virus 9 (VDV-9), and replication of two honey bee associated viruses, including both DWV-A and -B genotypes, suggesting that mites are biological vectors for important bee pathogens. We show that the antiviral RNAi response can be used define the host range of viruses in host-parasite interactions, such as honey bees and their parasites, enabling a better understanding of the role of a vector in the evolution and spread of honey bee pathogens.

genetics↗

bioRxiv2023

Predictive links between petal color and pigment quantities in natural Penstemon hybrids

Flowers have evolved remarkable diversity in petal color, in large part due to pollinator-mediated selection. This diversity arises from specialized metabolic pathways that generate conspicuous pigments. Despite the clear link between flower color and floral pigment production, studies determining predictive relationships between pigmentation and petal color are currently lacking. In this study, we analyze a dataset consisting of hundreds of natural Penstemon hybrids that exhibit variation in flower color, including blue, purple, pink, and red. For each individual hybrid, we measured anthocyanin pigment content and petal spectral reflectance. We found that floral pigment quantities are correlated with hue, chroma, and brightness as calculated from petal spectral reflectance data: hue is related to the relative amounts of delphinidin vs. pelargonidin pigmentation, whereas brightness and chroma are correlated with the total anthocyanin pigmentation. We used a partial least squares regression approach to identify predictive relationships between pigment production and petal reflectance. We find that pigment quantity data provide robust predictions of petal reflectance, confirming a pervasive assumption that differences in pigmentation should predictably influence flower color. Moreover, we find that reflectance data enables accurate inferences of pigment quantities, where the full reflectance spectra provide much more accurate inference of pigment quantities than spectral attributes (brightness, chroma, and hue). Our predictive framework provides readily interpretable model coefficients relating spectral attributes of petal reflectance to underlying pigment quantities. These relationships represent key links between genetic changes affecting anthocyanin production and ecological functions of petal coloration.

systems biology↗