Turtle genome provides new clues to vertebrate evolution

Study conducted by researchers Aurora Ruiz-Herrera(UAB) and Nicole Valenzuela from Iowa State University (USA), with contributions from the Institute for Evolutionary Biology (CSIC-UPF) and Earlham College, highlight the importance of the role of chromatin – the three-dimensional structure in which genetic material is folded and packaged inside the cell nucleus – in regulating gene function and its influence on evolution and speciation.

The researchers assembled de novo (without a prior reference model) the complete genomes of two species of cryptoterranean turtles, commonly called short-necked turtles, by combining sequencing and gene expression technologies.

These are two lineages in which sex chromosomes evolved independently: one with XX/XY chromosomes (the type found in humans and other mammals) and the other with ZZ/ZW chromosomes (present in birds and butterflies).

Moreover, they identified a new three-dimensional chromatin conformation in both lineages: in addition to fusion and fission events in the linear genomes, they discovered a pattern of chromosome folding that allows interactions between centromeres and telomeres.

The findings provide new information about the three-dimensional structure of chromatin in amniotes, a phylogenetic group that includes reptiles, birds and mammals.

“We propose that the divergent pattern found in turtles arose from a condition that existed in an amniote ancestor that had a nuclear configuration with extensive associations between its chromosomes. These associations have been preserved during linear genome rearrangements in turtles and other vertebrates,” says Valenzuela. .

Ruiz-Herrera from UAB emphasizes: “The results expand our knowledge of the evolution of sex chromosomes and offer a strong basis for future studies of genome evolution and chromosome organization in vertebrates.”

Key model for scientific research

In the article, the researchers emphasize that studying the turtle genome provides important information that could change our understanding of biology and evolution. Their longevity and disease resistance make them a unique model for scientific research ranging from biomedicine to species conservation.

Sequencing its genome is key to identifying the genes responsible for these traits and could lead to advances in human medicine, especially in areas such as aging and disease resistance.

Moreover, the turtle genome provides a unique window into evolution: these reptile species have been around for more than 250 million years, meaning they have survived mass extinctions and have been able to adapt to different habitats. Studying their DNA helps to better understand adaptation and survival mechanisms that are key to the conservation of turtles themselves, as well as other endangered species.

The first assemblies of turtle genomes were published more than ten years ago. Since then, twelve chelone genome assemblies have been reported, nine of them with identified gene sequences.

“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,” concludes Ruiz-Herrera.

Link:

Basanta Bista et al. “De novo genome assemblies of two cryptodiranian turtles with sex chromosomes ZZ/ZW and XX/XY provide insight into genome shuffling patterns and reveal novel three-dimensional genome structure in amniotes.” Genomic research.