Transcriptomic and Epigenetic Responses to Environmental Stress in Marine Bivalves with a Focus on Harmful Algal Blooms

Authors

Maria Victoria Suarez Ulloa, Florida International UniversityFollow

Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Major/Program

Biology

First Advisor's Name

Jose M. Eirin-Lopez

First Advisor's Committee Title

Committee Chair

Second Advisor's Name

Heather Bracken-Grissom

Second Advisor's Committee Title

Committee Member

Third Advisor's Name

Mauricio Rodriguez-Lanetty

Third Advisor's Committee Title

Committee Member

Fourth Advisor's Name

Eric Bishop-von Wettberg

Fourth Advisor's Committee Title

Committee Member

Fifth Advisor's Name

Giri Narasimhan

Fifth Advisor's Committee Title

Committee Member

Keywords

Transcriptomics, Epigenetics, Environmental Stress, Harmful Algal Blooms, Marine Toxins, Histones, DNA Methylation, Gene Expression, Bivalves, Mussels, Oysters

Date of Defense

6-7-2017

Abstract

Global change poses new threats for life in the oceans forcing marine organisms to respond through molecular acclimatory and adaptive strategies. Although bivalve molluscs are particularly tolerant and resilient to environmental stress, they must now face the challenge of more frequent and severe Harmful Algal Blooms (HABs) episodes. These massive outbreaks of microalgae produce toxins that accumulate in the tissues of these filter-feeder organisms, causing changes in their gene expression profiles, which in turn modify their phenotype in order to maintain homeostasis. Such modifications in gene expression are modulated by epigenetic mechanisms elicited by specific environmental stimuli, laying the foundations for long-term adaptations.

The present work aims to examine the links between environmental stress in bivalve molluscs (with especial emphasis on Harmful Algal Blooms) and specific epigenetic marks triggering responses through modifications in gene expression patterns. Overall, a better understanding of the molecular strategies underlying the conspicuous stress tolerance observed in bivalve molluscs will provide a framework for developing a new generation of biomonitoring strategies. In addition, this strategy will represent a valuable contribution to our knowledge in acclimatization, adaptation and survival.

With that goal in mind, the present work has generated transcriptomic data using RNA-Seq and microarray technologies, facilitating the characterization and investigation of the epigenetic mechanisms used by the Mediterranean mussel Mytilus galloprovincialis during responses to HAB exposure. That information was made publicly available through a specialized online resource (the Chromevaloa Database, chromevaloa.com) assessing the response of chromatin-associated transcripts to Okadaic Acid.

Specific epigenetic marks have been assessed under lab-controlled exposure experiments simulating the natural development of the HAB Florida Red Tide (FRT). Results demonstrate a role for the phosphorylation of histone H2A.X and DNA methylation in the response to FRT in the Eastern oyster Crassostrea virginica. Lastly, the study of co-expression networks based on RNA-Seq data series from the Pacific oyster Crassostrea gigas reveals dynamic transcriptomic patterns that vary with time, stressor and tissue. However, consistent functional profiles support the existence of a core response to general conditions of environmental stress. Such response involves metabolic and transport processes, response to oxidative stress and protein repair or disposal, as well as the activation of immune mechanisms supporting a tightly intertwined neuroendocrine-immune regulatory system in bivalves.

Identifier

FIDC001905

ORCID

orcid.org/0000-0002-6199-0656

Creative Commons License

This work is licensed under a Creative Commons Attribution-No Derivative Works 4.0 License.

Recommended Citation

Suarez Ulloa, Maria Victoria, "Transcriptomic and Epigenetic Responses to Environmental Stress in Marine Bivalves with a Focus on Harmful Algal Blooms" (2017). FIU Electronic Theses and Dissertations. 3461.
https://digitalcommons.fiu.edu/etd/3461