Initial molecular-level response to artificial selection for increased aerobic metabolism. Myodes glareolus

We analyzed the liver and heart transcriptomes of bank voles (Myodes (=Clethrionomys) glareolus) that had been selected for increased aerobic metabolism. The organs were sampled from 13th generation voles; at that point, the voles from four replicate selected lines had 48% higher maximum rates of oxygen consumption than those from four control lines. At the molecular level, the response to selection was primarily observed in gene expression: over 300 genes were found to be differentially expressed between the selected and control lines and transcriptome-wide pattern of expression distinguished selected lines from controls. No evidence for selection-driven changes of allele frequencies at coding sites was found: no SNP changed frequency more than expected under drift alone and frequency changes aggregated over all SNPs did not separate selected and control lines. Nevertheless, among genes which showed highest differentiation in allele frequencies between selected and control lines we identified, using information about gene functions and the biology of the selected phenotype, plausible candidate targets of selection genes; these genes, together with those identified in expression analysis have been prioritized for further studies. Because our selection lines were derived from a natural population, the amount and the spectrum of variation available for selection probably closely approximated that typically found in populations of small mammals. Therefore our results are relevant to the understanding of the molecular basis of complex adaptations occurring in natural vertebrate populations.