UC Davis

This dissertation explored the physiological and evolutionary implications of histone post-translational modifications (PTMs) as epigenetic marks. It began with the development of methods to reliably analyze histone PTMs in non-model organisms. These methods were applied to Mozambique tilapia (Oreochromis mossambicus) to uncover how salinity stress in a euryhaline fish impacts histone PTMs in the gills, kidney, and testes. Further experimentation was performed to investigate how histone PTMs in the gills are impacted through time when Mozambique tilapia are exposed to salinity challenges during specific developmental stages. Several key results emerged from this dissertation, including the following. First, the methods developed for histone PTM analysis enabled the quantification of 503 biologically relevant histone PTMs, which were shown to exhibit remarkable tissue-specificity in the gills, kidney, and testes of Mozambique tilapia. Second, salinity stress was shown to induce a histone PTM response in both the gills and testes, signifying a potential for histone PTMs to play a role in salinity acclimation and adaptation, respectively. Third, ambient salinity was shown to elicit an unexpectedly slow, widespread, and enduring response of histone PTMs in the gills. Extending beyond the context of Mozambique tilapia, this dissertation advances histone PTM research in ecological contexts. It enables a comprehensive analysis of histone PTMs in non-model organisms and reveals the timescale through which histone PTMs are likely to respond to environmental conditions.