Study Identifies Novel Chromatin Configuration in Turtle Genomes

Researchers from UAB and Iowa State University have produced the first-ever genome assemblies of two hidden-neck turtle species. These findings, which uncovered a previously unknown three-dimensional genome structure within the phylogenetic group that includes reptiles, birds, and mammals, will aid in developing more effective turtle conservation strategies and advance the study of vertebrate genome evolution and chromosomal organization.

The study, led by researchers Aurora Ruiz-Herrera (UAB) and Nicole Valenzuela (Iowa State University) with contributions from the Institute of Evolutionary Biology (CSIC-UPF) and Earlham College, was published in Genome Research.

It underscores the crucial role of chromatin—the three-dimensional structure in which genetic material is folded and packaged within the cell nucleus—in regulating gene function and influencing evolution and speciation.

Scientists constructed full genome assemblies for two species of short-necked turtles without relying on existing reference models. They utilized a combination of gene sequencing and expression methods to achieve this.

These turtle species represent distinct lineages with independently evolved sex chromosome systems: one employs XX/XY (similar to mammals), while the other uses ZZ/ZW (as found in avian species and lepidopterans).

Furthermore, the study revealed a novel three-dimensional chromatin configuration in both lineages. This configuration involves a chromosomal folding pattern enabling interactions between centromeres and telomeres, which goes beyond the previously known fusion and fission events in linear genomes.

These findings offer fresh insights into the three-dimensional chromatin structure of amniotes, a group encompassing reptiles, birds, and mammals.

We suggest that the divergent pattern found in the turtles originated from an existing amniote ancestral state defined by a nuclear configuration with extensive associations between its chromosomes that were preserved during linear genome reshuffling in turtles and other vertebrates.”

Nicole Valenzuela, Researcher, Department of Ecology, Evolution and Organismal Biology, Iowa State University

“These findings broaden our knowledge about the evolution of sex chromosomes and provide a solid foundation for future research on genome evolution and chromosome organization in vertebrates,” highlights Aurora-Ruiz Herrera, a researcher in the Department of Cell Biology, Physiology and Immunology and the Institute of Biotechnology and Biomedicine (IBB) of the UAB.

Key Model for Scientific Research

The article emphasizes the significance of analyzing turtle genomes for advancing the knowledge of biological processes and evolutionary mechanisms. Turtles' exceptional lifespan and disease resilience make them valuable subjects for scientific research across various fields, including biomedicine and conservation efforts.

Unraveling their genetic code is essential for identifying the specific genes linked to these characteristics, potentially leading to breakthroughs in human health, particularly in areas such as longevity and immune function.

Furthermore, turtle genomes provide a distinctive lens to examine evolutionary history. These ancient reptiles have persisted for over a quarter of a billion years, enduring global catastrophes and adapting to a wide range of habitats.

Investigating their genetic makeup enhances the comprehension of adaptive and survival strategies, which is crucial for preserving not only turtle species but also other forms of life.

Over ten years have passed since the initial publication of turtle genome assemblies. In the intervening period, researchers have released a total of twelve genome assemblies for various Chelonian species. Among these, nine assemblies include annotated gene sequences.

The newly generated assemblies are now added to this list and reflect the importance of high-quality genomic resources for the advancement of evolutionary and developmental biology.”

Aurora-Ruiz Herrera, Researcher, Department of Cell Biology, Universitat Autònoma de Barcelona