Browsing by Author "Stathopoulos, Sofia"

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    Genetic signatures for enhanced olfaction in the African mole-rats
    (Public Library of Science, 2014) Stathopoulos, Sofia; Bishop, Jacqueline M; O'Ryan, Colleen
    The Olfactory Receptor (OR) superfamily, the largest in the vertebrate genome, is responsible for vertebrate olfaction and is traditionally subdivided into 17 OR families. Recent studies characterising whole-OR subgenomes revealed a ‘birth and death’ model of evolution for a range of species, however little is known about fine-scale evolutionary dynamics within single-OR families. This study reports the first assessment of fine-scale OR evolution and variation in African mole-rats (Bathyergidae), a family of subterranean rodents endemic to sub-Saharan Africa. Because of the selective pressures of life underground, enhanced olfaction is proposed to be fundamental to the evolutionary success of the Bathyergidae, resulting in a highly diversified OR gene-repertoire. Using a PCR-sequencing approach, we analysed variation in the OR7 family across 14 extant bathyergid species, which revealed enhanced levels of functional polymorphisms concentrated across the receptors’ ligand-binding region. We propose that mole-rats are able to recognise a broad range of odorants and that this diversity is reflected throughout their OR7 gene repertoire. Using both classic tests and tree-based methods to test for signals of selection, we investigate evolutionary forces across the mole-rat OR7 gene tree. Four well-supported clades emerged in the OR phylogeny, with varying signals of selection; from neutrality to positive and purifying selection. Bathyergid life-history traits and environmental niche-specialisation are explored as possible drivers of adaptive OR evolution, emerging as non-exclusive contributors to the positive selection observed at OR7 genes. Our results reveal unexpected complexity of evolutionary mechanisms acting within a single OR family, providing insightful perspectives into OR evolutionary dynamics.
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    The tangled history of olfaction in African mole-rats, Bathyergidae: insights from Olfactory Receptor genes
    (2012) Stathopoulos, Sofia; Bishop, Jacqueline M; O'Ryan, Colleen
    This thesis reports the first assessment of OR variation in Bathyergidae, and therefore, the first for a family of subterranean mammals. Using a PCR-sequencing approach, 178 unique OR sequences, corresponding to 119 unique OR genes are characterised from 14 mole-rat species. Bathyergidae OR genes are classified using sequence similarity and phylogenetic comparison with more than 50 mammalian OR subgenomes.