The Role of DNA Methylation in Arthropods.
thesisposted on 17.01.2020 by Hollie Jade Marshall
In order to distinguish essays and pre-prints from academic theses, we have a separate category. These are often much longer text based documents than a paper.
Epigenetic mechanisms, such as DNA methylation, are poorly understood in arthropods compared to mammals and plants. Arthropods have been shown to display a variety
of DNA methylation profiles across species, making them ideal for understanding the function of DNA methylation outside of a mammalian context. This thesis explores the
role of DNA methylation in two arthropod species; the eusocial bumblebee, Bombus terrestris and the freshwater crustacean Daphnia magna.
Previous research has implicated DNA methylation in caste determination in some social insect species. I have found differentially methylated genes between worker castes
of B. terrestris, some of which are involved in reproduction. However, there was no direct link with differentially expressed genes. This indicates DNA methylation does
not causally affect gene expression differences between castes.
Another possible function of DNA methylation in B. terrestris is the regulation of imprinted genes. Imprinted genes are those which display parent-of-origin allele-specific
expression. Predictions based on the kinship theory state imprinted genes should exist in B. terrestris. I have identified parent-of-origin expression in this species, indicating
some support for the kinship theory. However, DNA methylation does not appear to be directly mediating this process.
The final chapter of this thesis identified DNA methylation changes through time in a single resurrected population of D. magna. A small number of genes which exhibited
DNA methylation changes over time were involved in the production of males, which is usually triggered by environmental change. The data generated in this chapter will be used for novel analyses investigating the adaptive potential of DNA methylation.
This thesis has contributed new knowledge to three fields: caste determination in social insects, imprinted genes in social insects and adaptive epigenetics. Taken as a whole, the studies presented here highlight the need for functional validation and the consideration of genotype in future ecological epigenetic research.