For decades, coral and coral reefs have been dying off . But a powerful new ally could be emerging: Scientists at Stanford have proven for the first time that the gene-editing process known as CRISPR can work on coral, offering hopes of making stronger breeds in the future.
Coral, one of the planet's most photogenic marine invertebrates, have suffered through for a number of manmade reasons: Overfishing, blast fishing using explosives, urban runoff, and ocean acidification through rising temperatures. Since the 1980s, the planet has seen three global coral bleaching events, where coral expel their symbiotic algae and become bone-white. The last one .
For Phillip Cleves, PhD, a postdoctoral scholar and geneticist at Stanford, the question of editing coral genes is wrapped up in the animal's survival: “Up until now, there hasn’t been a way to ask whether a gene whose expression correlates with coral survival actually plays a causative role. There’s been no method to modify genes in coral and then ask what the consequences are," he in a press release.
Corals aren't the most natural candidates for the CRISPR process due to their breeding process. Most coral spawn only once or twice a year in October or November when triggered by a full moon. In a brief window, coral release sperm and eggs into the ocean where they meet and become zygotes. There's not much time before the zygotes, fertilized single cells, start multiplying. Cleves, with help from colleagues at the Australian Institute of Marine Science and UT-Austin, had to get the lunar and breeding cycles just right.
Once they got ahold of their zygotes, they proceeded to target three coral genes: red fluorescent protein, green fluorescent protein, and fibroblast growth factor 1a. The first two are related to coral's distinctive look, the third is believed to be related to coral growth in new colonies.
With the fluorescent proteins, Cleves and his colleagues thought they would be able to easily identify if their process had worked. They tried to knock out the glow, figuring their results would be easily seen. But coral, it turns out, has multiple copies of its green and red fluorescent proteins. Take one out and another just takes its place. The glow remained.
"Although we are not sure we saw convincing loss of fluorescence, DNA sequencing showed us that we were able to molecularly target both the red and the green fluorescent protein genes," Cleves said.
With the third, fibroblast growth factor 1a, they were able to see clear results. Post-CRISPR sequencing showed largely mutated embryos, making the test a success.
The point of the experiment wasn't to create a race of uber-coral capable of dominating the world, but rather, Cleves says, to "figure out the basic mechanisms of how coral works."
The world's coral conservationists, and just about anybody who cares about the remarkable animal that provides living ecosystems for so many fish, have grown increasingly worried about the future of reefs across the globe in recent years.
Cleves calls it an "all-hands-on-deck moment."
"If we can start classifying what genes are important, then we can get an idea of what we can do to help conservation, or even just to predict what going to happen in the future. And I think that makes this a really exciting time to be a basic biologist looking at the genetics of coral.”