Date of Award

2013

Degree Type

Thesis

Degree Name

Master of Science in Biological and Environmental Sciences (MSBES)

Department

Fisheries, Animal and Veterinary Science

First Advisor

Marta Gomez-Chiarri

Abstract

The Eastern oyster Crassostrea virginica, an ecologically and economically important estuarine organism, suffers mortalities as high as 90-100% in affected areas due to Roseovarius Oyster Disease (ROD), caused by the bacterial pathogen, Roseovarius crassostreae. Advanced genotypic breeding techniques necessitate information regarding markers and genes associated with disease resistance. As yet, the host-pathogen interaction between C. virginica and R. crassostreae is poorly understood at the molecular level. The identification of potential genes and pathways responsible for an effective host defense response in the Eastern oyster to R. crassostreae is important not only to provide a basis for enhanced breeding techniques, but also to enhance understanding of innate immunity in a broader, evolutionary sense. The present study proposed to uncover not only genes and general processes potentially involved in disease resistance to ROD in the Eastern oyster, but also diversified gene families. To that end the present study entailed a disease challenge exposing RODresistant and ROD-susceptible families of oysters to R. crassostreae, highthroughput cDNA sequencing of samples from several timepoints throughout the disease challenge, assembly of sequence data into a reference transcriptome, analysis of the transcriptome through differential gene expression and gene family similarity clustering, and single nucleotide polymorphism (SNP) detection to identify candidate gene markers. Oyster resistance to R. crassostreae was found to involve extracellular matrix remodeling, cell adhesion, inflammation, metabolism, and other processes. Several gene families identified as putatively diversified and important in the oyster host defense response were enumerated and described, including serine proteases, serine protease inhibitors, c-type lectins, C1q domain-containing proteins, fibrinogen domain-containing proteins, scavenger receptors with class B SRCR domains, interferon-induced protein 44 (IFI44) family proteins, and GTPase of the immunity associated protein (GIMAP) family proteins. Further, similarity clustering of proteins and translated transcripts from diverse invertebrates suggested that GIMAP proteins are expanded in molluscs and IFI44 proteins are expanded in bivalves.

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