Abstract
BackgroundWe describe the genome of the western painted turtle, Chrysemys picta bellii, one of the most widespread, abundant, and well-studied turtles. We place the genome into a comparative evolutionary context, and focus on genomic features associated with tooth loss, immune function, longevity, sex differentiation and determination, and the species' physiological capacities to withstand extreme anoxia and tissue freezing.ResultsOur phylogenetic analyses confirm that turtles are the sister group to living archosaurs, and demonstrate an extraordinarily slow rate of sequence evolution in the painted turtle. The ability of the painted turtle to withstand complete anoxia and partial freezing appears to be associated with common vertebrate gene networks, and we identify candidate genes for future functional analyses. Tooth loss shares a common pattern of pseudogenization and degradation of tooth-specific genes with birds, although the rate of accumulation of mutations is much slower in the painted turtle. Genes associated with sex differentiation generally reflect phylogeny rather than convergence in sex determination functionality. Among gene families that demonstrate exceptional expansions or show signatures of strong natural selection, immune function and musculoskeletal patterning genes are consistently over-represented.ConclusionsOur comparative genomic analyses indicate that common vertebrate regulatory networks, some of which have analogs in human diseases, are often involved in the western painted turtle's extraordinary physiological capacities. As these regulatory pathways are analyzed at the functional level, the painted turtle may offer important insights into the management of a number of human health disorders.
Highlights
We describe the genome of the western painted turtle, Chrysemys picta bellii, one of the most widespread, abundant, and well-studied turtles
Using cDNAs obtained through 454 sequencing of libraries derived from brain, testes, ovaries, and trunk, we identified a total of 40,091 exons within 7,961 gene models to which cDNAs could be mapped
We identified the majority of turtle pseudo-exons in their chromosomally syntenic regions when compared to other amniotes (Figure 4), consistent with the very slow rate of genomic change seen in chelonians
Summary
We describe the genome of the western painted turtle, Chrysemys picta bellii, one of the most widespread, abundant, and well-studied turtles. As the vertebrate paleontologist Alfred Romer noted half a century ago, ‘The chelonians are the most bizarre, and yet in many respects the most conservative, of reptilian groups Because they are still living, turtles are commonplace objects to us; were they entirely extinct, [they] would be a cause for wonder’ [1]. The living crown group of turtles extends back at least 210 million years [3] and is characterized by a number of unique morphological and physiological features Besides their distinctive shell, turtles have extremely long lifespans, are often reproductively active at very advanced ages, often determine sex by the temperature at which eggs incubate, are the most anoxia-tolerant tetrapods known, and have the capacity in some species to freeze nearly solid, thaw, and survive with negligible tissue damage. The western painted turtle genome harbors a wealth of information on the genetic basis of these and other adaptations that characterize this unique vertebrate lineage
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
