LE3 .A278 2011

2011

Gibson, Glenys

Acadia University

Bachelor of Science

Honours

Biology

Biology

Many organisms exhibit developmental plasticity, whereby the environment affects development and generates alternate phenotypes in young. The developmental mechanisms that lead to this plasticity are largely unknown. My hypothesis is that epigenetic modifications (e.g., histone methylation) lead to changes in gene transcription during embryonic development that result in alternate phenotypes, and that these modifications are altered by environmental factors such as diet. The spionid polychaete Polydora cornuta is an excellent model for this investigation: these worms produce two distinct larval morphs within a single egg capsule. Adelphophagic young are large, quick to develop, and eat non-developing nurse eggs within the capsule, whereas planktotrophic young are small, slow to develop, and eat plankton only after hatching. My objective was to use immunofluorescence to screen for several epigenetic modifications throughout development in the two larval morphs. Furthermore, I tested for changes in epigenetic modifications in young whose mothers were fed diets rich in methyl donors (e.g., folate/vitamin B12). Major results included: (1) variation in onset and distribution of some epigenetic modifications (e.g., H3K14 acetylation) among different tissues throughout development, suggesting a link with cell differentiation; (2) earlier onset of one modification (H3K9 monomethylation) in planktotrophic larvae; and (3) hypermonomethylation (e.g., of H3K9) in young produced by females fed enhanced diets. These results indicate that changes in the onset and distribution of specific epigenetic modifications at certain ontogenetic stages may lead to developmental plasticity, and that these modifications may indeed be influenced by maternal diet.

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https://scholar.acadiau.ca/islandora/object/theses:756