Anthozoas: Saving the Corals Using Genetic Engineering
I’m sure you know corals are the beautiful biotic structures living in our oceans. I’m also sure you know our corals are dying.
Climate change once again makes an appearance in this situation. From agriculture to industry, our Earth is emitting tons of greenhouse gases into our atmosphere. It is very easy to think that the Earth will adapt to our actions. However, with the alarming increases in carbon emissions, oceanic ecosystems are not able to adapt fast enough. The net result, mass populations of dying corals.
Coral Bleaching
A few ago, coral bleaching sparked a lot of attention after it was found that the El Niño was the longest and most damaging to the corals. El Nino refers to a phase in which waters get irregularly warmer near the Pacific region.
How coral bleaching works
As carbon levels increase, more heat gets trapped within our atmosphere. More heat in the atmosphere means more heat being absorbed by our oceans. As temperature rises, corals start to suffer.
Corals have a mutualistic relationship with a type of algae called zooxanthellae (zoa-zen-thel-i). Mutualistic meaning that they both rely on each other for something. Here’s how it works:
Corals allow the algae to live in their tissues, and the algae perform photosynthesis to provide food for the corals.
Think about it like this; the zooxanthellae are subletting tons of apartments in the endodermal tissue of these corals.
The issue is that when it gets too warm, the algae starts to produce reactive oxygen species (ROS). These corals react to the ROS by expelling the algae from their tissue. In other words, the corals have evicted the algae.
Once they’re expelled, the coral begins to die. Their source of food is gone! By reducing the number of zooxanthellae in their cells, these corals also lose their bright colours thus turn a pale white (ie. bleached).
Note that the corals don’t die right away. Sometimes the algae can come back when the environment is more stable, however warming waters are reducing the chances of the algae actually coming back.
In fact, more than 50% of the corals on Earth are already dead.
Understanding ROS
Reactive oxygen species play a major role in the relationship between coral and algae. There are 3 types:
- Hydrogen Peroxide (H2O2)
- Superoxide anion (O2 -)
- Hydroxyl Radical (OH•)
The interesting thing about ROS is that algae are already aware of them! They have an antioxidant system to cope with the harmful effects, however, as oxidative stress increases, the efficiency of the system decreases.
For algae, there are 2 lines of defence. The first one includes antioxidant enzymes and the second one includes repair enzymes.
The purpose of these defence systems is to convert the ROS into stable ions.
The Role of GR
Glutathione Reductase (GR) is a common flavoprotein that controls the amount of Glutathione (GSH) present in the algae cells.
The “bad” or oxidized version of GSH is called “GSSG”. An increased GSSG-to-GSH ratio indicates oxidative stress because normally 90% of the glutathione is in its reduced form (GSH). That’s where glutathione reductase comes in.
GR is able to control this GSH-GSSG ratio by keeping the glutathione in its reduced (GSH) form. GSH is then used by glutathione peroxidase to convert hydrogen peroxide to just water molecules
Although there are different types of enzymes and proteins that are in the line of defence for the algae. GR plays a major role in suppressing the oxidized version of GSH from accumulating which in turn contributes to the well-being of the algae! However, as the oceans lose their welcoming environment to climate change these systems are not as efficient.
What if there was a way to introduce glutathione reductase into the corals so that they too could resist the harmful effects of these reactive oxygen species? A double whammy perhaps?
Introducing: Anthozoas
At Anthozoas we are leveraging genetic engineering to insert the GR encoding gene into species of corals that are going extinct in Australia namely the Staghorn and Elkhorn Corals.
The Process
- Collecting zygotes
Corals expel their gametes (a process called spawning) only twice a year. We can predict this using the full moon cycle. We would prepare 2–3 days in advance and take a coral sample from the water during October/November.
2. CRISPR/Cas-9. 🧬
We have already identified a gene that we would like to test out in a coral sample. GSR is a mammalian, GR protein-encoding gene. By inserting this gene into the zygote using CRISPR technology, the corals would build resistance to the reactive oxygen species (ROS). Thus improving their lifespan as they would not need to evict their lovely photosynthesizing tenants (algae).
How it works
- Attach the single guide RNA to the Cas-9 protein.
The Cas-9 acts as the scissors. By snipping some base pairs of the zygotes DNA, the sgRNA will direct the Cas-9 to the correct site.
The barrier for this process to work is determining which sequence will be able to be knocked out. Since only 2 types of coral have been genetically sequenced, we would be able to figure out the section of the DNA to could knock out and eventually replace with the GSR gene.
2. Insert the GSR gene
Once the Cas-9 is in the right spot, it will snip those base pairs creating a double-strand break (DSB). Once this is done, the GSR gene can be inserted into the DNA sequence.
3. Colonization
After tests have been conducted to see the efficiency of the gene insertion and phenotypic representation, we would introduce the zygotes back into the oceans. These zygotes are fertilized gametes that have the capability of colonizing. Once introduced back into these oceans, they are referred to as planula. Planulae float in the ocean, settle on a substrate, and grow into a new coral colony!
Corals are Key
- Corals provide more than 500 million people around the world with jobs, income, and coastal defence.
- They even capture 25% of the carbon dioxide from our atmosphere. As deforestation continues, we need to protect what we have in our oceans to facilitate carbon capture.
- 25% of ALL marine life is dependant on corals as their home. By protecting these corals from the harmful effects of coral bleaching, we can regain ocean biodiversity which will, in turn, help the tourism and healthcare industry.
Corals are not plants. They are animals. There are too many factors that are killing corals at rates that are getting increasingly disturbing. Innovation is the only way we can help our corals.
Our mission at Anthozoas is to protect corals that are going extinct in the Great Barrier Reef from harmful ROS by leveraging genetic engineering techniques.
Thank you for reading! If you have any questions, feel free to email me and/or visit our website www.anthozoas.com! Anthozoas is a moonshot project built by myself, Neyla Kirby, Zahra Ahmed and Selina Liu. 🐬
