Tracking the ghost of the genome: The epigenetics of pollution adaptation in an environmental sentinel

Rasnaca, Ilze 2019. Tracking the ghost of the genome: The epigenetics of pollution adaptation in an environmental sentinel. PhD Thesis, Cardiff University. Item availability restricted.

Preview	PDF - Accepted Post-Print Version Download (5MB) | Preview
	PDF (Cardiff University Electronic Publication Form) - Supplemental Material Restricted to Repository staff only Download (333kB)

Abstract

Understanding the long-term impacts of pollution and pesticides is important for environmental protection and management of chemical risks. Such knowledge can also provide a better understanding of evolutionary adaptation to stress. In this project, the transgenerational effects of toxicants and underlying epigenetic molecular mechanisms of effects within and between generations in earthworms are explored. Long-term chronic transgenerational exposures and field assessments were used to establish the phenotypic, genetic and epigenetic consequences of long-term exposure to a trace metal (Cd), a metalloid (As) and a pesticide (the neonicotinoid imidacloprid). Results from exposures of the earthworms Eisenia fetida and Eisenia andrei over three generations show that exposure to environmentally realistic concentrations of arsenic causes a mild hormetic effect on reproduction after one generation of exposure followed by a detrimental effect on growth after further continuous exposure and on survival regardless of whether worms are later kept in a control or spiked environment. Similar exposure to cadmium resulted in a detrimental impact on growth during the first generation, after which the earthworms adapted to this exposure in subsequent generations. Continuous Imidacloprid exposure reduced growth rates for three generations. Some degree of cumulative effect on rates of survival were seen (i.e. effect increasing in each generation) up to three generations of exposure. No transgenerational effects were observed. To further understand the mechanistic and epigenetic effect of long-term exposure, a study was undertaken to investigate global gene expression responses in a population of the earthworm species Lumbricus rubellus resident at a long-term heavily polluted site associated with the Avonmouth zinc and lead smelter compared to L. rubellus from an unpolluted reference population. Results from a common garden transplant experiment for the two populations indicated that many basic cellular processes, such as cytoskeleton reorganisation, protein phosphorylation and gene expression were affected as a result of the exposure to metal pollution from the smelter source. Genes important in chromatin reorganisation were shown to be involved in adaptation to the heavy metal exposure and that a difference in global DNA methylation was present in L. rubellus adapted to living in heavily polluted soil compared to control individuals. In a laboratory study, a difference in DNA methylation was also found in L. rubellus after a life-time exposure to fluoranthene, but not arsenic or cadmium. This may point to a role for other epigenetic mechanisms (e.g. histone modification) in the chromatin remodelling response seen in the field.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Biosciences
Subjects:	Q Science > Q Science (General)
Date of First Compliant Deposit:	24 February 2020
Last Modified:	29 Mar 2021 09:23
URI:	https://orca.cardiff.ac.uk/id/eprint/129909

Actions (repository staff only)

Edit Item