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- Keehnen, Naomi, et al.
(författare)
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Geographic variation in hemocyte diversity and phagocytic propensity shows a diffuse genomic signature in the green veined white butterfly
- 2024
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Insects rely on their innate immune system to successfully mediate complex interactions with their internal microbiota, as well as the microbes present in the environment. Given the variation in microbes across habitats, the challenges to respond to them is likely to result in local adaptation in the immune system. Here we focus upon phagocytosis, a mechanism by which pathogens and foreign particles are engulfed in order to be contained, killed and processed for antigen presentation. We investigated the phenotypic and genetic variation related to phagocytosis, in two allopatric populations of the butterfly Pieris napi. We found that the populations differ in their hemocyte composition, and overall phagocytic capability, driven by the increased phagocytic propensity of each cell type. However, no evidence for divergence in phagocytosis-related genes was observed, though an enrichment of genes involved in glutamine metabolism was found, which have recently been linked to immune cell differentiation in mammals.
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- Keehnen, Naomi L. P., et al.
(författare)
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The consequences of surviving infection across the metamorphic boundary : tradeoff insights from RNAseq and life history measures
- 2024
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The broad diversity of insect life has been shaped, in part, by pathogen pressure, yet the influence of injury and infection during critical periods of development is understudied. During development, insects undergo metamorphosis, wherein the organism experiences a dramatic shift in their overall morphology, and physiology. In temperate zones, metamorphosis is often directly followed by a developmental arrest called diapause, for which the insect needs to acquire enough energy reserves before the onset of winter. We investigated the long-term effects of injury and infection using two bacteria in the butterfly Pieris napi, revealing that the negative consequences of bacterial infection carry across the metamorphic boundary. Initial direct effects of infection were weight loss and slower development, as well as an increased mortality at higher infection levels. The detrimental effects were stronger in the gram-positive Micrococcus luteus compared to gram-negative Escherichia coli. Transcriptome-wide differences between the two bacteria were already observed in the gene expression profile of the first 24 hours after infection. Larvae infected with M. luteus showed a strong suppression of all non-immunity related processes, with several types of immune responses being activated. The impact of these transcriptomic changes, a tradeoff between homeostasis and immune response, were visible in the life history data, wherein individuals infected with M. luteus had the highest mortality rate, along with the lowest pupal weight, developmental rate and adult weight of all the treatments. Overall, we find that the cost of infection and wounding in the final larval instar carries over the metamorphic boundary, and is expected to negatively affect their lifetime fitness.
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- Lindestad, Olle, et al.
(författare)
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Analyzing the neutral and adaptive background of butterfly voltinism reveals structural variation in a core circadian gene
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Many insects exhibit geographic variation in voltinism, the number of generations produced per year. This includes high-latitude species in previously glaciated areas, implying divergent selection on life cycle traits during or shortly after recent colonization. Here, we use a whole-genome approach to genetically characterize a set of populations of the butterfly Pararge aegeria that differ in voltinism. We construct a high-quality de novo genome for P. aegeria, and assess genome-wide genetic diversity and differentiation between populations. We then use the inferred phylogeographic relationships as the basis for a scan for loci showing signs of divergent selection associated with voltinism differences. The genic outliers detected include population-specific mutations of circadian loci, most notably a locally fixed 97-amino acid deletion in the circadian gene timeless. Variation in timeless has previously been implicated as underlying variation in life cycle regulation in wild populations in our study species, as well as in other insects. These results add to a growing body of research framing circadian gene variation as a mechanism for generating local adaptation of life cycles.
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- Lindestad, Olle, et al.
(författare)
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Context-dependent candidate genes : a test of within-population genetic variation for photoperiodic plasticity
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Components of the circadian clock have been implicated as involved in photoperiodic regulation of diapause across various insect groups, hence contributing to adaptation to adverse seasonal conditions. Such studies typically involve either characterization of nondiapause mutants, or comparisons of populations differing in diapause induction thresholds, leaving within-population variation unexplored. Here, we present a test of the effects on diapause induction of within-population variation at two circadian loci, timeless and period, in the butterfly Pararge aegeria. Variation at both loci has previously shown to be associated with diapause induction on an interpopulation level. However, in the present study, no effect on induction was found of either locus at a within-population level. Examination of sequence data revealed novel variation at both timeless and period in the studied population. We hypothesize that selection for a northern-type life cycle may have promoted compensatory variants, ensuring a high rate of diapause induction despite the presence of southern, diapause-averting SNP alleles. Additionally, both timeless and period showed considerable variation across Scandinavian populations, with an unusually high rate of nonsynonymous substitutions compared to the rest of the genome, raising new questions about the fine-scale adaptive dynamics of circadian genes.
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