Sex and the symbiont: Can algae hookups help corals survive?
Rice biologists' discovery can be used to help climate-challenged reefs survive for now

Date:
September 22, 2021
Source:
Rice University
Summary:
Scientists have discovered that symbiotic single-celled algae that
live inside of and feed corals can reproduce not only by mitosis,
but also sexually. Encouraging sex in these algae can accelerate
their evolution to produce strains better able to help reefs cope
with climate change.



FULL STORY ==========================================================================
A little more sexy time for symbionts could help coral reefs survive
the trials of climate change. And that, in turn, could help us all.


========================================================================== Researchers at Rice University and the Spanish Institute of Oceanography already knew the importance of algae known as dinoflagellates to the
health of coral as the oceans warm, and have now confirmed the tiny
creatures not only multiply by splitting in half, but can also reproduce through sex.

That, according to Rice marine biologist Adrienne Correa and graduate
student Lauren Howe-Kerr, opens a path toward breeding strains of dinoflagellate symbionts that better serve their coral partners.

Dinoflagellates not only contribute to the stunning color schemes of
corals, but critically, they also help feed their hosts by converting
sunlight into food.

"Most stony corals cannot survive without their symbionts," Howe-Kerr
said, "and these symbionts have the potential to help corals respond to
climate change. These dinoflagellates have generation times of a couple
months, while corals might only reproduce once a year.

"So if we can get the symbionts to adapt to new environmental
conditions more quickly, they might be able to help the corals survive
high temperatures as well, while we all tackle climate change." In an open-access study in Nature's Scientific Reports, they wrote the discovery "sets the stage for investigating environmental triggers" of symbiont
sexuality "and can accelerate the assisted evolution of a key coral
symbiont in order to combat reef degradation."


==========================================================================
To better understand the algae, the Rice researchers reached out to
Rosa Figueroa, a researcher at the Spanish Institute of Oceanography
who studies the life cycles of dinoflagellates and is lead author on
the study.

"We taught her about the coral-algae system and she taught us about sex
in other dinoflagellates, and we formed a collaboration to see if we
could detect symbiont sex on reefs," Howe-Kerr said.

"In genomic datasets of coral dinoflagellates, researchers would see all
the genes coral symbionts should need to reproduce sexually, but no one
had been able to see the actual cells in the process," said Correa, an assistant professor of biosciences. "That's what we got this time." The discovery follows sampling at coral reefs in Mo'orea, French Polynesia,
in July 2019 and then observation of the algae through advanced confocal microscopes that allow for better viewing of three-dimensional structures.

"This is the first proof that these symbionts, when they're sequestered
in coral cells, reproduce sexually, and we're excited because this opens
the door to finding out what conditions might promote sex and how we can
induce it," Howe-Kerr said. "We want to know how we can leverage that
knowledge to create more genetic variation." "Because the offspring of dividing algae only inherit DNA from their one parent cell, they are, essentially, clones that don't generally add to the diversity of a
colony. But offspring from sex get DNA from two parents, which allows
for more rapid genetic adaptation," Correa said.



========================================================================== Symbiont populations that become more tolerant of environmental stress
through evolution would be of direct benefit to coral, which protect
coastlines from both storms and their associated runoff.

"These efforts are ongoing to try to breed corals, symbionts and any
other partners to make the most stress-resistant colonies possible,"
Correa said.

"For coral symbionts, that means growing them under stressful conditions
like high temperatures and then propagating the ones that manage to
survive.

"After successive generations we'll select out anything that can't
tolerate these temperatures," she said. "And now that we can see there's
sex, we can do lots of other experiments to learn what combination of conditions will make sex happen more often in cells. That will produce symbionts with new combinations of genes, and some of those combinations
will hopefully correspond to thermotolerance or other traits we want. Then
we can seed babies of the coral species that host that symbiont diversity
and use those colonies to restore reefs." The research was supported
by the Spanish Ministry of Science and Innovation and the European
Community Project (DIANAS-CTM2017-86066-R), a Lewis and Clark Grant from
the American Philosophical Society, a Wagoner Foreign Study Scholarship,
the National Science Foundation (1635798) and an early-career research fellowship from the Gulf Research Program of the National Academy of
Sciences (2000009651).

Read the paper at https://doi.org/10.1038/s41598-021-98148-9.

This news release can be found online
at https://news-network.rice.edu/news/ 2021/09/22/sex-and-the-symbiont-can-algae-hookups-help-corals-survive/
Follow Rice News and Media Relations via Twitter @RiceUNews.

Related materials: Algae team rosters could help
ID 'super corals': https://news.rice.edu/2020/02/ 12/algae-team-rosters-could-help-id-super-corals/ Houston
flooding polluted reefs more than 100 miles offshore: http:// news.rice.edu/2021/04/06/houston-flooding-polluted-reefs-more-than-100-miles- offshore-2/ Correa Lab: http://www.owlnet.rice.edu/~ac53/index.html
Department of Earth, Environmental and Planetary Sciences:
https:// earthscience.rice.edu Wiess School of Natural Sciences: https://www.rice.edu Video: https://youtu.be/Alc179zwuK8 A dinoflagellate tetrad cell that will soon split into four separate cells, captured by
Rice University scientists through a confocal microscope. The cell's four nuclei are depicted in red. Researchers at Rice and in Spain determined
from experiments that these symbionts, taken from a coral colony in
Mo'orea, French Polynesia, are able to reproduce both through mitosis
and via sex. (Credit: Correa Lab/Rice University) Images for download: https://news-network.rice.edu/news/files/2021/09/0927_CORAL-1-WEB.jpg
Rice University's Lauren Howe-Kerr, left, and Adrienne Correa
discovered that symbiont algae found on corals in French Polynesia
are able to reproduce via mitosis and sex. That could make it easier
to develop algae that better protect coral reefs from the effects
of climate change. (Credit: Photo by Brandon Martin/Rice University) https://news-network.rice.edu/news/files/2021/09/0927_CORAL-2-WEB.jpg
A coral of the type studied by scientists at Rice University is
protected by dinoflagellates (inset), algae that turn sunlight
into food to feed and protect reefs. The study showed the algae
are able to reproduce via sex, opening a path toward accelerated
evolution of strains that can better protect coral from the
effects of climate change. (Credit: Inset by Carsten Grupstra/Rice
University; coral image by Andrew Thurber/Oregon State University) https://news-network.rice.edu/news/files/2021/09/0927_CORAL-3-WEB.jpg A dinoflagellate tetrad cell that will soon split into four separate cells, captured by Rice University scientists through a confocal microscope. The cell's four nuclei are depicted in red. Researchers at Rice and in Spain determined from experiments that these symbionts, taken from a coral
colony in Mo'orea, French Polynesia, are able to reproduce both through
mitosis and via sex. (Credit: Correa Lab/Rice University) Located on a
300-acre forested campus in Houston, Rice University is consistently
ranked among the nation's top 20 universities by U.S. News & World
Report. Rice has highly respected schools of Architecture, Business,
Continuing Studies, Engineering, Humanities, Music, Natural Sciences and
Social Sciences and is home to the Baker Institute for Public Policy. With 4,052 undergraduates and 3,484 graduate students, Rice's undergraduate student-to-faculty ratio is just under 6-to-1. Its residential college
system builds close-knit communities and lifelong friendships, just one
reason why Rice is ranked No. 1 for lots of race/class interaction and
No. 1 for quality of life by the Princeton Review.

Rice is also rated as a best value among private universities by
Kiplinger's Personal Finance.

========================================================================== Story Source: Materials provided by Rice_University. Note: Content may
be edited for style and length.


========================================================================== Journal Reference:
1. R. I. Figueroa, L. I. Howe-Kerr, A. M. S. Correa. Direct evidence
of sex
and a hypothesis about meiosis in Symbiodiniaceae. Scientific
Reports, 2021; 11 (1) DOI: 10.1038/s41598-021-98148-9 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/09/210922181520.htm

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