Surprises in sea turtle genes could help them adapt to a rapidly
changing world

Date:
February 7, 2023
Source:
University of Massachusetts Amherst
Summary:
Around 100 million years ago, a group of land-dwelling turtles
took to the oceans, eventually evolving into the sea turtles that
we know today.

However, the genetic foundations that have enabled them to thrive
in oceans throughout the world have remained largely unknown.


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FULL STORY ========================================================================== Around 100 million years ago, a group of land-dwelling turtles took
to the oceans, eventually evolving into the sea turtles that we know
today. However, the genetic foundations that have enabled them to
thrive in oceans throughout the world have remained largely unknown. In research recently published in the Proceedings of the National Academy of Sciences, an international team of 48 researchers led by the University
of Massachusetts Amherst in collaboration with the Leibniz Institute for
Zoo and Wildlife Research and the Vertebrate Genome Project revealed an incredibly detailed genetic map of two species - - green and leatherback turtles -- which is packed with surprises that might hold the key to
their survival in a rapidly changing world.


==========================================================================
A single species' genome contains the genetic set of instructions used
to build that species, and sequencing any species' genome is an enormous
amount of work.

This is akin to translating an entire library into a language
that scientists can read and has only been possible in the last few
decades. For green sea turtles, a "draft" genome, including approximately 100,000 pieces of genetic information, has been available since 2013,
"but" says Blair Bentley, a postdoctoral researcher in environmental conservation at UMass Amherst and the lead author of the new research,
"these pieces of genetic information weren't precisely mapped out. It
was as if you walked into a library and found 100,000 pages lying
on the floor." To more precisely catalogue the turtles' genomes,
the international team turned to new technologies including long read sequencing -- a technique recently named 2022 Method of the Year by
the journal Nature. This has made it possible to sequence genomes from virtually any living species and to do so with far more accuracy than was previously possible. Sequencing of the turtles' genomes was performed
both at Rockefeller University, in the Vertebrate Genome Laboratory
(VGL), led by Erich Jarvis, who chairs the VGP, and Olivier Fedrigo who
is director of the VGL, and at the Max Planck Institute of Molecular
Cell Biology and Genetics by Eugene Myers -- all coauthors on the new
study. "These advances allowed us to do the equivalent of shelving
everything according to the Dewey Decimal System so that we can begin
to understand how everything fits together," says Bentley.

Once Bentley and his co-authors had correctly organized and annotated
the genetic data, they started finding surprises. The first is that,
though greens and leatherbacks diverged from a common ancestor about 60
million years ago, their genomes are remarkably similar.

Similar, but not the same. "It's those differences that make them unique,"
says Lisa Komoroske, professor of environmental conservation at UMass
and one of the paper's two senior authors. And it's those differences
that may hold the key to each species' long-term survival, especially considering that populations of both greens and leatherbacks have seen precipitous declines due to human activity.

It turns out that green turtles have evolved more genes dedicated
to immunity, suggesting an immune system that is better prepared for
new pathogens, as well as more olfactory receptors -- they have better
senses of smell. The leatherback genome also shows that they lower genetic diversity and have historically had lower population levels. "This is both
a blessing and a curse," says Komoroske, "because it means that, while leatherbacks are a resilient species, there isn't much genetic diversity
for them to evolve to meet the challenges of their rapidly changing environment." Insights such as these will help conservation biologists
make more informed decisions about how best to protect these animals as
they face the challenges of adapting to our rapidly changing planet.

Furthermore, the more time Bentley and Komoroske spent in the turtles'
genomes, the more it became clear that much of the genetic differences
between the two species is to be found, not on the macrochromosomes,
but on what was once considered to be "genetic junk": microchromosomes,
or small genetic bits that seem not to exist in mammals but are
characteristic of avian and reptilian genomes. "We found most of
the divergences between the green and the leatherbacks on these microchromosomes," says Camila Mazzoni, a researcher at the Leibniz
Institute for Zoo and Wildlife Research and the study's other senior
author, "and our work feeds into the growing scholarship on the importance
of microchromosomes in vertebrate evolution." "The only way we could
do this work at all was through an incredible collaborative network that brought scientists from different fields together with organizations like
the Vertebrate Genome Project and NOAA Fisheries' Southwest Fisheries
Science Center, supported by funders from around the world," says
Komoroske. Indeed, the research was supported by the National Science Foundation, National Oceanic and Atmospheric Administration, Max Planck Institute of Molecular Cell Biology and Genetics, National Institutes
of Health, Howard Hughes Medical Institute, Vertebrate Genomes Project,
Sanger Institute, Sa~o Paolo Research Foundation, German Federal Ministry
of Education and Research, Generalitat de Catalunya, la Caixa Foundation, Vienna Science and Technology Fund, City of Vienna, Welsh Government
Se^r Cymru II, European Union's Horizon 2020 research and innovation
program under the Marie Skłodowska-Curie grant, the Florida Sea
Turtle Grants Program, and individual international donors.

* RELATED_TOPICS
o Plants_&_Animals
# Evolutionary_Biology # Biology # Endangered_Animals
o Earth_&_Climate
# Environmental_Policy # Environmental_Awareness #
Sustainability
o Fossils_&_Ruins
# Evolution # Origin_of_Life # Early_Humans
* RELATED_TERMS
o Sea_turtle o Turtle o Snapping_turtle o Ocean o Dinosaur o
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========================================================================== Story Source: Materials provided by
University_of_Massachusetts_Amherst. Note: Content may be edited for
style and length.


========================================================================== Journal Reference:
1. Blair P. Bentley, Toma's Carrasco-Valenzuela, Elisa K. S. Ramos,
Harvinder Pawar, Larissa Souza Arantes, Alana Alexander, Shreya M.

Banerjee, Patrick Masterson, Martin Kuhlwilm, Martin Pippel,
Jacquelyn Mountcastle, Bettina Haase, Marcela Uliano-Silva, Giulio
Formenti, Kerstin Howe, William Chow, Alan Tracey, Ying Sims,
Sarah Pelan, Jonathan Wood, Kelsey Yetsko, Justin R. Perrault,
Kelly Stewart, Scott R. Benson, Yaniv Levy, Erica V. Todd,
H. Bradley Shaffer, Peter Scott, Brian T.

Henen, Robert W. Murphy, David W. Mohr, Alan F. Scott, David
J. Duffy, Neil J. Gemmell, Alexander Suh, Sylke Winkler, Franc,oise
Thibaud-Nissen, Mariana F. Nery, Tomas Marques-Bonet, Agostinho
Antunes, Yaron Tikochinski, Peter H. Dutton, Olivier Fedrigo,
Eugene W. Myers, Erich D.

Jarvis, Camila J. Mazzoni, Lisa M. Komoroske. Divergent sensory and
immune gene evolution in sea turtles with contrasting demographic
and life histories. Proceedings of the National Academy of Sciences,
2023; 120 (7) DOI: 10.1073/pnas.2201076120 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/02/230207161248.htm

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