Date of Award

7-23-2024

Publication Type

Thesis

Degree Name

M.Sc.

Department

Biological Sciences

Keywords

Adaptation;Epigenetics;Evolution;Maternal Effects;Methylation

Supervisor

Daniel Heath

Abstract

Maternal effects are a prevalent source of early life phenotypic variation in offspring across diverse taxa. Maternal effects have also been shown to provide an adaptive advantage corresponding to maternal environmental stimuli. There are several well studied examples of adaptive maternally induced intergenerational effects in response to the parental environment mediated by mechanisms such as stress hormones and nutrients. DNA methylation is a fundamental cellular process that affects gene transcription and can respond rapidly to changing environments yet remains a largely unexplored mechanism for maternal effect signaling. We manipulated the maternal environment by reducing food availability and increasing day length in Chinook salmon (Oncorhynchus tshawytscha). We used a factorial breeding design as well as gene-specific sequencing assays to analyze maternal effect induced DNA methylation variation in the offspring. We found significant maternal effects on gene-specific DNA methylation, as well as heightened levels of maternal effects in response to an increase in maternal photoperiod. We report higher maternal effects in early life stages that decline through development in four gene functional categories: growth, immune response, metabolic function, and histone protein regulation. Despite a resetting of the methylome following embryogenesis, we provide evidence that maternal effects can modulate gene-specific DNA methylation variation and that effect is sensitive to the environment the mothers experience. This pattern of maternal effects responding to maternal environment are consistent with a fundamental process driving adaptive intergenerational phenotypic variation.

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