# Gene Editing Corals: A Lifeline Against Climate Change
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Understanding Coral Resilience
The Reengineering Life series from Future Human explores groundbreaking advancements in genetic technology and their impact on humanity and the environment. In 2016, the Australian Bureau of Meteorology reported record-high sea temperatures near the Great Barrier Reef, the largest coral reef system globally. This prolonged heat wave resulted in the most severe bleaching event recorded, with nearly 30% of its coral population perishing.
Rising ocean temperatures, a byproduct of climate change, pose a significant threat to coral reefs, leading to further bleaching and mass mortality. These reefs support approximately 25% of all marine species at some point in their life cycle, protect coastal regions from storms and erosion, and sustain local economies.
To combat the imminent collapse of these ecosystems, researchers are urgently investigating why certain corals thrive while others perish. Central to this inquiry are the genes that contribute to coral survival. Employing the CRISPR gene-editing technique, a team of scientists has identified a gene linked to heat resistance in corals from the Great Barrier Reef.
Section 1.1 The Role of CRISPR in Coral Research
The findings, recently published in the Proceedings of the National Academy of Sciences, could steer coral conservation initiatives and possibly pave the way for a genetic test akin to 23andMe for corals. This test could help scientists identify which coral species are most vulnerable to bleaching and which might possess greater resilience, as noted by lead author Phillip Cleves, PhD, a marine geneticist at the Carnegie Institution for Science.
“The main challenge in our field has been pinpointing the genes that influence coral bleaching and survival under heat stress,” Cleves explains. “Previously, we lacked the genetic tools necessary to investigate these functions.”
Subsection 1.1.1 Pioneering CRISPR Techniques in Coral
Researchers have successfully adapted CRISPR for coral applications. This powerful tool acts like genetic scissors, enabling scientists to modify or delete specific genes within the cells of organisms. While CRISPR has seen extensive use in lab mice and is being tested in humans for various genetic disorders, its application in corals presents unique challenges.
One significant hurdle is that CRISPR interventions must occur in newly fertilized coral eggs, which are produced only once a year during a full moon. During this event, mature corals synchronize the release of their eggs and sperm into the ocean for fertilization. For several years, Cleves and his team have traveled to Australia’s Great Barrier Reef to collect these eggs for their studies.
“It’s certainly a logistical challenge,” he admits.
Section 1.2 Experimental Insights
In the laboratory, Cleves and his collaborators used fine needles to inject CRISPR into the fertilized coral eggs, targeting a gene known to be important for heat response in other species. After allowing the eggs to develop, they exposed the resulting coral larvae to varying water temperatures.
The edited larvae thrived at 27 degrees Celsius (approximately 81 degrees Fahrenheit) but quickly succumbed at 34 degrees (93 degrees Fahrenheit). In contrast, unedited larvae survived well in the warmer conditions, indicating that the targeted gene is crucial for heat tolerance. Water temperatures around the Great Barrier Reef typically range from 23 degrees Celsius (75 degrees Fahrenheit) in winter to 29 degrees Celsius (84 degrees Fahrenheit) in summer. Notably, the gene HSF1 had not previously been recognized as significant for heat response in corals.
When exposed to excessive heat, corals expel the beneficial algae residing in their tissues. These algae not only provide vibrant color but are also essential for the nutrients corals need to survive. The absence of algae causes corals to lose their color and increases their susceptibility to disease. Bleaching also stifles coral growth and reproduction.
“This research enhances our understanding of the mechanisms behind coral bleaching during heat stress, which is invaluable as we strive to comprehend how corals can adapt to climate change,” comments Helen Fox, PhD, conservation science director at the Coral Reef Alliance, a California-based nonprofit.
Chapter 2 Perspectives on Genetic Engineering
In 2018, Cleves and his colleagues were pioneers in demonstrating the feasibility of gene editing in coral, though initial attempts did not yield sufficient results to effect noticeable changes in coral traits. This recent study, however, indicates that gene editing can effectively delete genes and assess the implications of their absence. Similar advancements have been made by marine biologists using CRISPR in squid.
“Being able to remove genes from coral will facilitate a better understanding of their function,” Cleves states. “This foundational knowledge will aid in deciphering how corals can withstand climate change and the biological processes involved.”
While Cleves does not advocate for creating genetically engineered corals, some collaborators, such as coral geneticist Madeleine van Oppen, PhD, are exploring the potential of CRISPR to develop hybrid corals that incorporate traits from various species, enhancing their heat tolerance.
In a commentary accompanying Cleves’ publication, van Oppen warns that CRISPR-generated coral strains may be classified as GMOs in certain regions, subjecting them to stringent regulatory and public scrutiny. Fox expresses caution regarding the prospect of genetically altering coral reefs, emphasizing that “nature is inherently unpredictable, and excessive human intervention may lead to unforeseen consequences.”
Moreover, bleaching is not the sole threat facing coral reefs. Most reefs exist in shallow waters near shorelines, rendering them susceptible to land-based pollution, coastal development, and fishing activities. Illegal coral mining, despite being prohibited in many nations, also exacerbates the decline of reefs globally.
For the time being, both van Oppen and Cleves concur that introducing genetically modified corals into natural environments should not be the primary focus of conservation strategies. Instead, they are optimistic that CRISPR can unveil alternative approaches to safeguard endangered coral species.
“A more sustainable conservation strategy involves mitigating threats to coral reefs and allowing natural evolution to proceed, enabling corals to adapt to climate change,” Fox concludes.