Are corals genetically equipped to survive climate change?

Date:
October 14, 2020
Source:
Okinawa Institute of Science and Technology (OIST) Graduate
University
Summary:
A research team has taken a close look at the genomes of fifteen
species in the coral genus, Acropora, to determine if they're
suited to a warmer ocean.



FULL STORY ==========================================================================
In 1998, ocean temperatures soared, and the world experienced its
first significant coral bleaching event. From the Great Barrier Reef
to Indonesia to Central America, corals turned white and ghostly. Many
of them died. And this was just a hint as to what was to come. Over the following two decades, the bleaching became more severe and more frequent,
with future predictions suggesting that this trend will continue. But
not all corals are affected equally.


========================================================================== "Acropora corals are especially susceptible to bleaching and are expected
to decline in the future," said Professor Noriyuki Satoh, from the Marine Genomics Unit at the Okinawa Institute of Science and Technology Graduate University (OIST). "This is an issue because Acropora corals are very important. They grow quickly compared to other corals, which helps with
reef growth, island formation, and coastal protection. And they also
provide a habitat for more than a million species of marine organisms."
To shed light on whether Acropora corals are genetically equipped to
handle a warmer ocean, researchers from OIST, the University of Tokyo
and Seikai National Fisheries Research Institute have sequenced and
analyzed the genomes of 15 species of Acropora coral, as well as three
species of coral from outside this genus.

A genome is the complete set of an organism's DNA and contains all
its genes, which, over hundreds of millions of years, have undergone
random mutations. By analyzing what mutations are shared across different species, scientists can come to understand when organisms evolved and when
they split from close relatives to form new species. This study, published
in Molecular Biology and Evolution, has revealed the evolutionary history
of Acropora corals, with some surprising results.

"We found that the Acropora ancestor diverged from other corals around 120 million years ago," Professor Satoh explained. "And the diversification
of Acropora corals, when we start to see a lot of different species
appear, occurred 25-60 million years ago. For both events, this is much
earlier than previously thought." This is an important find as it means
that Acropora diversified when the world's oceans were much warmer than
today. They then experienced an ice age and survived, which hints that
they could have the genetic make-up to handle vast changes in temperature.

Lead author Dr. Chuya Shinzato, a former staff scientist at OIST and
now an Associate Professor at the University of Tokyo, analyzed the
genomes and found that these 15 species could be divided into four
groups. Dr. Shinzato and the group then compared in detail which genes
had been conserved and which genes were lost.

It was revealed that before this coral genus diversified, several
mutations occurred which saw it gain 28 additional gene families. These
genes likely contributed to this diversification, as well as the genus's success at spreading across the globe and its ability to handle a range
of temperatures.

"There were three notable additions from this time period, which could
allow these corals to withstand high-stress environments," Professor
Satoh said. "Two of these have been identified before and are associated
with responding to environmental stress, usually heat." But the finding
of the third gene, which encodes DMSP lyase, is significant as this
is the first time that a genome analysis has revealed its existence
in Acropora corals. This gene allows the corals to produce a compound,
dimethyl sulfide, in the water that, when transferred into the air, aids
in the formation of clouds. This suggests that when temperatures get too
high, the Acropora corals might be able to create small cloud umbrellas,
which can protect them by providing shade and filtering out the light.

Although this research has shed light on the evolutionary history of an important genus of coral, Professor Satoh emphasized that it is still
hard to say whether this genus will be able to survive the predicted
ocean warming and coral bleaching events. "Yes, Acropora corals have
withstood vast changes in temperature in the past and, yes, they have
these genes that might allow them to somewhat mitigate extreme heat,
but the speed in which current climate change is occurring might still
exceed their ability to adapt. On the other hand, this vast information
of coral genomes provides a basis for future studies of coral biology." Alongside Professor Satoh and Dr. Shinzato, the research team also
included Dr.

Konstantin Khalturin, Dr. Jun Inoue, Dr. Yuna Zayazu, Dr. Miyuki Kanda,
and Ms.

Mayumi Kawamitsu from OIST, Mr. Yuki Yoshioka from the University of
Tokyo, and Dr. Hiroshi Yamashita and Dr. Go Suzuki from the Seikai
National Fisheries Research Institute.


========================================================================== Story Source: Materials provided by Okinawa_Institute_of_Science_and_Technology_(OIST)
Graduate_University. Original written by Lucy Dickie. Note: Content may
be edited for style and length.


========================================================================== Journal Reference:
1. Chuya Shinzato, Konstantin Khalturin, Jun Inoue, Yuna Zayasu, Miyuki
Kanda, Mayumi Kawamitsu, Yuki Yoshioka, Hiroshi Yamashita,
Go Suzuki, Noriyuki Satoh. Eighteen Coral Genomes Reveal the
Evolutionary Origin of Acropora Strategies to Accommodate
Environmental Changes. Molecular Biology and Evolution, 2020;
DOI: 10.1093/molbev/msaa216 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/10/201014201011.htm

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