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2 results on '"Humble, Emily"'

1. Evidence of positive selection associated with placental loss in tiger sharks.

Author

Swift DG, Dunning LT, Igea J, Brooks EJ, Jones CS, Noble LR, Ciezarek A, Humble E, and Savolainen V

Subjects
Animals, Base Sequence, Female, Male, Phylogeny, Pregnancy, Reproduction, Sharks genetics, Transcriptome, Placenta, Selection, Genetic, Sharks physiology
Abstract

Background: All vertebrates initially feed their offspring using yolk reserves. In some live-bearing species these yolk reserves may be supplemented with extra nutrition via a placenta. Sharks belonging to the Carcharhinidae family are all live-bearing, and with the exception of the tiger shark (Galeocerdo cuvier), develop placental connections after exhausting yolk reserves. Phylogenetic relationships suggest the lack of placenta in tiger sharks is due to secondary loss. This represents a dramatic shift in reproductive strategy, and is likely to have left a molecular footprint of positive selection within the genome., Results: We sequenced the transcriptome of the tiger shark and eight other live-bearing shark species. From this data we constructed a time-calibrated phylogenetic tree estimating the tiger shark lineage diverged from the placental carcharhinids approximately 94 million years ago. Along the tiger shark lineage, we identified five genes exhibiting a signature of positive selection. Four of these genes have functions likely associated with brain development (YWHAE and ARL6IP5) and sexual reproduction (VAMP4 and TCTEX1D2)., Conclusions: Our results indicate the loss of placenta in tiger sharks may be associated with subsequent adaptive changes in brain development and sperm production.

Published
2016
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2. Substitutions in the Glycogenin-1 Gene Are Associated with the Evolution of Endothermy in Sharks and Tunas

Author

Ciezarek, Adam G., Dunning, Luke T., Jones, Catherine S., Noble, Leslie R., Humble, Emily, Stefanni, Sergio S., Savolainen, Vincent, and The Leverhulme Trust

Subjects
Fish Proteins, endothermy, sharks, Sharks/genetics, Body Temperature, Evolution, Molecular, Glucosyltransferases/genetics, 0603 Evolutionary Biology, Tuna/genetics, positive selection, Animals, Fish Proteins/genetics, Selection, Genetic, Muscle, Skeletal, Glycoproteins, 0604 Genetics, Muscle, Skeletal/metabolism, Tuna, Glycoproteins/genetics, phylogenetics, Glucosyltransferases, Body Temperature/genetics, Transcriptome, human activities, Developmental Biology, Research Article
Abstract

Despite 400–450 million years of independent evolution, a strong phenotypic convergence has occurred between two groups of fish: tunas and lamnid sharks. This convergence is characterized by centralization of red muscle, a distinctive swimming style (stiffened body powered through tail movements) and elevated body temperature (endothermy). Furthermore, both groups demonstrate elevated white muscle metabolic capacities. All these traits are unusual in fish and more likely evolved to support their fast-swimming, pelagic, predatory behavior. Here, we tested the hypothesis that their convergent evolution was driven by selection on a set of metabolic genes. We sequenced white muscle transcriptomes of six tuna, one mackerel, and three shark species, and supplemented this data set with previously published RNA-seq data. Using 26 species in total (including 7,032 tuna genes plus 1,719 shark genes), we constructed phylogenetic trees and carried out maximum-likelihood analyses of gene selection. We inferred several genes relating to metabolism to be under selection. We also found that the same one gene, glycogenin-1, evolved under positive selection independently in tunas and lamnid sharks, providing evidence of convergent selective pressures at gene level possibly underlying shared physiology.

Published
2016
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