Analysis of DNA Methylation in HSP Genes and Its Contribution to Thermal Plasticity in Diploptera punctata

Abstract

Recent empirical studies have shown that epigenetic mechanisms are highly associated with the mediation of phenotypic plasticity. Investigation of the functional significance of these mechanisms holds the potential for understanding the molecular basis of phenotypic plasticity. In this thesis, I report the outcome of my MPhil study which involves investigating the contribution of the epigenetic variation, within the protein coding regions of heat shock protein (HSP) genes, to the phenotypic variation in a non-model organism (a viviparous cockroach species, Diploptera punctata). In the first part of my study, I obtained the DNA sequences of two major HSP genes, Hsp70 and Hsp90, of D. punctata; these represent two novel DNA sequences that have not previously been reported in this species. The method of amplifying these genes involves a universal primer design which benefits from the available sequence data of other phylogenetically related cockroach species. The second part of my study involves DNA methylation analysis at particular CpG sites within HSP genes. In this analysis, DNA samples are obtained from individual cockroaches which were reared at four different thermal conditions. Various life history traits of these individuals were also measured in order to find a correlation between DNA methylation and thermal plasticity of these phenotypes. Taking the DNA methylation and phenotypic data together, has enabled statistical analyses and additional observations that test several predictions which aim to find correlations between: 1) variation in DNA methylation and phenotypic variation, 2) environmental temperature and DNA methylation and finally 3) DNA methylation flexibility and the reaction norms of distinct genotypes to temperature. Methylation analysis provided that the CpG sites, within the coding regions of HSP genes, are highly methylated and this is predominantly affected by temperature. DNA methylation is also mostly related to body size of the cockroaches compared to other life history traits.

Date of Award	31 Dec 2019
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Matthew Cobb (Supervisor) & Reinmar Hager (Supervisor)