The Fate of Duplicated Regions of the Atlantic Salmon (Salmo Salar) Genome [microform]

The Fate of Duplicated Regions of the Atlantic Salmon (Salmo Salar) Genome [microform]
Author: Leslie Mitchell
Publisher: Library and Archives Canada = Bibliothèque et Archives Canada
Total Pages: 264
Release: 2004
Genre: Atlantic salmon
ISBN: 9780494035382

Gene and genome duplications have played a major role in vertebrate evolution. Salmonids provide a useful resource for studying the consequences of these events as their common ancestor underwent a genome duplication between 25 and 120 miliion years ago. To understand how a genome reorganizes itself to cope with duplicated chromosomes and the importance of gene duplications for evolution and adaptation, homeologous regions of the Atlantic salmon genome were identified and studied within a large insert, genomic BAC library; these BACs contain the metallothionen event. A BAC from each region was subsequently shotgun subcloned and sequenced. Sequence analysis revealed the presence of 10 genes, retaining their collinearity between the BAcs, although pseudogenization events have occurred in one of the duplicate loci in two instances. Comparative genomic analysis revealed the existence of extraordinary conservation of syntney over time.

Evolution and Characterization of the Fatty Acid-binding Proteins (fabps) in Atlantic Salmon (Salmo Salar)

Evolution and Characterization of the Fatty Acid-binding Proteins (fabps) in Atlantic Salmon (Salmo Salar)
Author: Yuk Yin Lai
Publisher:
Total Pages: 0
Release: 2012
Genre: Atlantic salmon
ISBN:

It is suggested that gene or genome duplication is the driving force in evolution that leads to speciation. Two models, the classical model and the duplication- degeneration-complementation (DDC) model, have been proposed on the fates of gene duplicates resulting from either a gene or a genome duplication event. The classical model suggests that one of the gene duplicates might result in loss of function (non- functionalization) or gain of a new function (neo-functionalization) depending on whether the accumulated mutations over the years are deleterious or beneficial to the organism. In the DDC model, it is proposed that each of the gene duplicates might accumulate different deleterious mutations in the regulatory region of the gene, such that these genes partition the ancestral gene function (sub-functionalization). Combinations of the phylogenetic analysis of many gene families support that salmonids have undergone two additional whole genome duplications compared to the mammals, one occurred in the common ancestors of teleosts and another happened in the common ancestor of salmonids approximately 25-120 million years ago. In this thesis, the evolution of the fatty acid-binding protein (fabp) family in fish and salmonids was examined. I have characterized eighteen unique fabp genes in Atlantic salmon. These include the seven fabp sub-families described previously in fish. Phylogenetic analyses and conservation of synteny support the two whole genome duplication events in the common ancestors of teleosts and salmonids and indicate when gene losses occurred. Genetic mapping of fabp gene duplicates to homeologous chromosomes in Atlantic salmon also support that they arose by the 4R genome duplication. I also searched for the signatures of neo-functionalization and sub-functionalization by calculating dN/dS ratios, examining the nature of amino acid substitutions and expression patterns, and suggested the fates of fabp gene duplicates in Atlantic salmon. Overall, the findings of this project provide insight into the evolutionary processes at play in salmonid genomes.

Identification and Annotation of Full-length Genes in Atlantic Salmon (Salmo Salar)

Identification and Annotation of Full-length Genes in Atlantic Salmon (Salmo Salar)
Author: Jong S. Leong
Publisher:
Total Pages: 0
Release: 2010
Genre: Atlantic salmon
ISBN:

Large-scale expressed sequence tags (ESTs) in Atlantic salmon (Salmo salar) are examined to answer questions regarding salmonid transcriptomes. ESTs represent raw and incomplete gene sequences that need to be read, assembled and analyzed with computer software. The goal of this thesis was to develop an automatically curated and publicly accessible set of annotated full-length genes, representing a near-complete transcript set for Salmo salar. In turn, these genes provide the framework for studies in gene expression, conservation, and molecular evolution. The work presented here also touches on the results of a molecular evolution study, as an example of how full-length gene identification can be used to answer biological questions. Previous to this study, a limited number of Atlantic salmon cDNA libraries and ESTs were known. To further the goal of determining complete gene sequences, highly enriched full-length cDNA libraries and full-length libraries were created and sequenced, resulting in the ability to identify a large number of full-length reference genes. Together, all libraries represent a diverse pool of transcriptome sequences for Salmo salar. The goal of producing an accurate large-scale full-length gene set on a duplicated genome is not trivial. Complete systems for this objective do not readily exist. EST sequencing, EST assembly, and data storage, are just a few of the initial computational issues that are addressed. Once these issues are resolved, the multi-step workflow of full-length gene determination is described. The final challenge involving the development of a concise and universally accessible system for visualization is discussed. The resulting computational framework that has been developed is shown to be able to handle the intricacies and the size of a duplicated salmonid genome. It has been largely accepted that Atlantic salmon have undergone a recent genome duplication. Gene paralogs provide one source of evidence for this event. Analysis of paralogs revealed signatures of asymmetric evolution possibly due to relaxation of selective pressure. This thesis provides a complete Bioinformatics analysis pipeline to analyze and to visualize a set of full-length reference genes for Atlantic salmon. Using full-length genes as a framework, the topic of molecular evolution was addressed to show evidence of asymmetrical evolution among gene duplicates. The full-length reference genes, along with ESTs and all putative transcripts, have been made publicly available. These results serve as a valuable genomic resource for next-generation sequencing and for all other salmonid research endeavours.

Repetitive Landscape of the Atlantic Salmon Genome

Repetitive Landscape of the Atlantic Salmon Genome
Author: Siemon Hian Siem Ng
Publisher:
Total Pages: 0
Release: 2006
Genre: Atlantic salmon
ISBN:

The duplication of genes and genomes is considered a major force in evolution. Ohno, in 1970, theorized that with two copies of the genome, one copy would be under normal evolutionary constraints while the other copy could serve as raw material for evolution. Salmonids are a classical example of species containing duplicated genomes, and they offer an opportunity to investigate how such genomes undergo reorganization as they attain a stable diploid state. Repetitive elements play an important role in genome reorganization. Therefore, I investigated the repeat structure and organization of the Atlantic salmon genome. An analysis of the fingerprinted CHORI-214 BACs classified the singletons, or those that contained few restriction sites, into three categories of repetitive structures. The first group contains histone genes in a tandemly repeating cluster of H4 - H2B - H1 - H2A - H3. A second group contains the ribosomal DNA (rDNA) cistron. Intriguingly, fluorescent in situ hybridization (FISH) analysis indicated that one of each of the duplicated histone and rDNA clusters was lost or rearranged in the genome. The remaining group of BACs contains novel repetitive sequences and tRNA clusters. The Atlantic salmon EST libraries and BAC-end sequences were data-mined for simple sequence repeats (SSRs) and 2,497 SSRs were recovered. 154 SSR loci gave clean PCR amplicons and 94 produced polymorphic banding patterns with eleven of the EST-SSRs indicating duplicated loci. These loci were mapped on the Atlantic salmon linkage map. Novel repetitive elements were detected in the sequences of Atlantic salmon BACs and ESTs. Using computational tools for data-mining, repetitive elements were identified and classified based on sequence similarity to other known repetitive elements such as SINES, LINEs and retrotransposons. A repeat database that can be used to mask repetitive elements, is now available for the Atlantic salmon genome. A website was developed to host the Atlantic salmon linkage and physical maps, correlating them based on marker hybridization. A BAC annotation pipeline analyzes the BAC sequences for ORFs, transcript similarity and repetitive elements. Information generated from sequence annotation, microsatellite development and repetitive element identification provides essential resources for investigating salmonid genomes.

Identification and Annotation of Full-length Genes in Atlantic Salmon (Salmo Salar)

Identification and Annotation of Full-length Genes in Atlantic Salmon (Salmo Salar)
Author: Jong S. Leong
Publisher:
Total Pages: 248
Release: 2010
Genre: Atlantic salmon
ISBN:

Large-scale expressed sequence tags (ESTs) in Atlantic salmon (Salmo salar) are examined to answer questions regarding salmonid transcriptomes. ESTs represent raw and incomplete gene sequences that need to be read, assembled and analyzed with computer software. The goal of this thesis was to develop an automatically curated and publicly accessible set of annotated full-length genes, representing a near-complete transcript set for Salmo salar. In turn, these genes provide the framework for studies in gene expression, conservation, and molecular evolution. The work presented here also touches on the results of a molecular evolution study, as an example of how full-length gene identification can be used to answer biological questions. Previous to this study, a limited number of Atlantic salmon cDNA libraries and ESTs were known. To further the goal of determining complete gene sequences, highly enriched full-length cDNA libraries and full-length libraries were created and sequenced, resulting in the ability to identify a large number of full-length reference genes. Together, all libraries represent a diverse pool of transcriptome sequences for Salmo salar. The goal of producing an accurate large-scale full-length gene set on a duplicated genome is not trivial. Complete systems for this objective do not readily exist. EST sequencing, EST assembly, and data storage, are just a few of the initial computational issues that are addressed. Once these issues are resolved, the multi-step workflow of full-length gene determination is described. The final challenge involving the development of a concise and universally accessible system for visualization is discussed. The resulting computational framework that has been developed is shown to be able to handle the intricacies and the size of a duplicated salmonid genome. It has been largely accepted that Atlantic salmon have undergone a recent genome duplication. Gene paralogs provide one source of evidence for this event. Analysis of paralogs revealed signatures of asymmetric evolution possibly due to relaxation of selective pressure. This thesis provides a complete Bioinformatics analysis pipeline to analyze and to visualize a set of full-length reference genes for Atlantic salmon. Using full-length genes as a framework, the topic of molecular evolution was addressed to show evidence of asymmetrical evolution among gene duplicates. The full-length reference genes, along with ESTs and all putative transcripts, have been made publicly available. These results serve as a valuable genomic resource for next-generation sequencing and for all other salmonid research endeavours.

Genome Mapping and Genomics in Fishes and Aquatic Animals

Genome Mapping and Genomics in Fishes and Aquatic Animals
Author: Thomas D. Kocher
Publisher: Springer Science & Business Media
Total Pages: 195
Release: 2008-06-07
Genre: Science
ISBN: 3540738371

Mapping of animal genomes has generated huge databases and several new concepts and strategies, which are useful to elucidate origin, evolution and phylogeny. Genetic and physical maps of genomes further provide precise details on chromosomal location, function, expression and regulation of academically and economically important genes. The series Genome Mapping and Genomics in Animals provides comprehensive and up-to-date reviews on genomic research on a large variety of selected animal systems, contributed by leading scientists from around the world. This volume summarizes the first era of genomic studies of aquaculture species, in which the tools and resources necessary to support whole-genome sequencing were developed. These tools will enhance efforts toward selective breeding of aquaculture species. Included in this volume are summaries of work on salmonids, cyprinids, catfish, tilapias, European sea bass, Japanese flounder, shrimps and oysters.