|
Archive.uky.edu >
The Graduate School (ETDs) >
Electronic Theses and Dissertations >
Please use this identifier to cite or link to this item:
http://hdl.handle.net/10225/146
|
| Title: | COMPARATIVE ANALYSIS OF FIVE COMPLETE AMBYSTOMATID SALAMANDER MITOCHONDRIAL GENOMES |
| Authors: | Samuels, Amy K. |
| Keywords: | Ambystoma
EST
axolotl
Bayesian
phylogeny |
| Date Created: | 2005 |
| Publisher: | University of Kentucky |
| Abstract: | In this study, mitochondrial transcript information from a recent EST project was
extended to obtain complete mitochondrial genome sequence for 5 tiger salamander
complex species (Ambystoma mexicanum, A. t. tigrinum, A. andersoni, A. californiense,
and A. dumerilii). For the first time, aspects of mitochondrial transcription in a
representative amphibian are described, and then complete mitochondrial sequence
data are used to examine salamander phylogeny at both deep and shallow levels of
evolutionary divergence. The available mitochondrial ESTs for A. mexicanum (N=2481)
and A. t. tigrinum (N=1205) provided 92% and 87% coverage of the mitochondrial
genome, respectively. Complete mitochondrial sequences for all species were rapidly
obtained by using long distance PCR and DNA sequencing. A number of genome
structural characteristics (base pair length, base composition, gene number, gene
boundaries, codon usage) were highly similar among all species and to other distantly
related salamanders. Overall, mitochondrial transcription in Ambystoma approximated
the pattern observed in other vertebrates. From the mapping of ESTs onto mtDNA it was
inferred that transcription occurs from both heavy and light strand promoters and
continues around the entire length of the mtDNA, followed by post-transcriptional
processing. However, the observation of many short transcripts corresponding to rRNA
genes indicates that transcription may often terminate prematurely to bias transcription
of rRNA genes; indeed an rRNA transcription termination signal sequence was observed
immediately following the 16S rRNA gene. Phylogenetic analyses of salamander family
relationships consistently grouped Ambystomatidae in a clade containing
Cryptobranchidae and Hynobiidae, to the exclusion of Salamandridae. This robust result
suggests a novel alternative hypothesis because previous studies have consistently
identified Ambystomatidae and Salamandridae as closely related taxa. Phylogenetic
analyses of tiger salamander complex species also produced robustly supported trees.
The D-loop, used in previous molecular phylogenetic studies of the complex, was found
to contain a relatively low level of variation and we identified mitochondrial regions with
higher rates of molecular evolution that are more useful in resolving relationships among
species. Our results show the benefit of using complete mitochondrial genome
information in studies of recently and rapidly diverged taxa. |
| URI: | http://hdl.handle.net/10225/146 |
| Appears in Collections: | Electronic Theses and Dissertations
|
Files in This Item:
| File |
Description |
Size | Format |
|---|
| SamuelsAK.pdf | | 309Kb | Adobe PDF | View/Open |
|
This item is protected by original copyright
|
Items in the archive are protected by copyright, with all rights reserved, unless otherwise indicated.
|
