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Evolutionary genetics of energetics
Energetic phenotypes, such as ATP levels, must be maintained as organisms adapt to differing ecologies. This project relates genomic change to biochemical change in energetic pathways with consequences for whole-organism performance. We are interested in the question: How do the pathways underlying largely homeostatic and conserved physiological systems nevertheless harbor variation within populations and evolve across species?
A. The glucose-6-phosphate (G6P) branchpoint
Traits such as glycogen storage, metabolic rate or flight performance are likely a function of flux through the G6P branchpoint in glycolysis. In D. melanogaster, we identified a genetic locus (QTL) underlying enzyme activities at the G6P branchpoint that also affects metabolic rate and flight velocity. This indicates that genetic variation in metabolic pathways can impact performance and motivates our use of enzymatic flux equations to model naturally-occurring variation in energetic traits as a function of variation in gene expression and enzyme activity at the G6P branchpoint.
B. Linking genomic, biochemical and physiological change on a phylogeny
Drosophilids are uniquely poised for a comparative approach to study the evolution of energetics. The genomes of twelve Drosophila species have been sequenced, and, in collaboration with David Rand (Brown University), we have assembled and analyzed the mitochondrial genomes of these species. We are attempting to model pathways such as the G6P branchpoint and mitochondrial oxidative phosphorylation in a phylogenetic context to test the hypothesis that relationships between genetic, biochemical and physiological variation within populations also hold for genetic and phenotypic divergence between species. This comparative approach measures traits among multiple genetic isolates within Drosophila species, available for the D. melanogaster, D. simulans, D. sechellia; the D. yakuba, D. teissieri, D. santomea; and the D. pseudoobscura, D. persimilis species groups. Using this experimental design we can scale between species phenotypic divergence by within species variation, shedding light on the evolutionary forces acting on physiological traits. For example, do populations harbor more phenotypic variation than expected given the amount of phenotypic divergence observed across the phylogeny?
Representative Publications:
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