Colubridae represents themost phenotypically diverse and speciose family of snakes, yet nowell-assembled and annotated genome exists for this lineage. Here, we report and analyze the genome of the garter snake, Thamnophis sirtalis, a colubrid snake that is an important model species for research in evolutionary biology, physiology, genomics, behavior, and the evolution of toxin resistance. Using the garter snake genome, we show how snakes have evolved numerous adaptations for sensing and securing prey, and identify features of snake genomestructure that provide insight into the evolution of amniote genomes.Analyses of the garter snake andother squamate reptile genomes highlight shifts in repeat element abundance andexpansionwithin snakes, uncover evidence of genes under positive selection, and provide revised neutral substitution rate estimates for squamates. Our identification of Z andW sex chromosome-specific scaffolds provides evidence for multiple origins of sex chromosome systems in snakes and demonstrates the value of this genome for studying sex chromosome evolution. Analysis of gene duplication and loss in visual and olfactory gene families supports a dim-light ancestral condition in snakes and indicates that olfactory receptor repertoires underwent an expansion early in snake evolution. Additionally, we provide some of the first links between secreted venom proteins, the genes that encode them, and their evolutionaryorigins ina rear-fanged colubridsnake, togetherwith newgenomic insight into the coevolutionary arms race between garter snakes and highly toxic newt prey that led to toxin resistance in garter snakes.
Bibliographical noteFunding Information:
We thank the production sequencing group at the McDonnell Genome Institute for assistance with genome sequencing, assembly and annotation, and John Abramyan for assistance with SCNA annotations in the chicken and turtle. The work was supported by funding from the National Human Genome Research Institute at National Institutes of Health [5U54HG00307907 to W.C.W.]; the National Science Foundation [DEB-1655571 and IOS-1655735 to T.A.C.]; a Natural Sciences and Engineering Research Council of Canada Discovery Grant [to B.S.W.C., K.B.S., and K.K.B.]; an Academia Sinica award [to C.H.K.]; a Minnesota Supercomputing Institute award [to S.E.M.]; and a Grand Challenges in Biology Postdoctoral Fellowship [to C.N.P.].
© The Author(s) 2018.
- Sex chromosomes
- Thamnophis sirtalis