Date of Award

Winter 2018

Project Type

Dissertation

Program or Major

Genetics

Degree Name

Doctor of Philosophy

First Advisor

Anita S. Klein

Abstract

The red alga Porphyra umbilicalis Kützing is an ecologically and economically important marine macroalga in the Northern Atlantic. Porphyra umbilicalis has a broad distribution within the North Atlantic. In the Northeast Atlantic, it is dioecious and reproduces both sexually and asexually, while in the Northwest Atlantic only asexual reproduction has been observed. As a high intertidal alga, P. umbilicalis regularly experiences desiccation and rehydration cycles with the tidal cycles, so it has high tolerance towards various abiotic stresses. The present work attempts to understand the population structure in asexual populations of P. umbilicalis in the Gulf of Maine by applying putative single nucleotide polymorphisms (SNP) markers developed from transcriptome data (Chapter 1). In order to understand the desiccation tolerance of P. umbilicalis, the contents of putative compatible solutes were measured and the genes involved in the synthesis of these solutes were analyzed in response to desiccation and rehydration treatments (Chapter 2). In addition, a comparative transcriptomic analysis was performed using P. umbilicalis under fresh, dehydrated, desiccated and rehydrated conditions in order to gain insights into the mechanisms of its desiccation tolerance in responses to water loss and water gain (Chapter 3). My work represents the first attempt to develop a suitable bioinformatic pipeline for RNA-seq to detect SNP markers for the red alga P. umbilicalis and to apply these SNP markers for population analysis. The compatible solutes study verifies the occurrences of nanomolar concentrations of trehalose in P. umbilicalis for the first time and identifies additional genes, possibly encoding trehalose phosphate synthases. The transcriptome study suggested distinct molecular responses may occur during dehydration and desiccation and confirmed that the rehydration-induced responses play an important role in the mechanisms of desiccation tolerance in P. umbilicalis.

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