Monday, May 15, 2023

Sea anemone’s sweet efforts help reef ecosystems flourish

KAUST researchers have discovered how corals can thrive in nutrient-depleted oceans. Their study shows how sea anemones are able to recycle the essential nutrient Nitrogen.
Photo Credit: Morgan Bennett-Smith / King Abdullah University of Science and Technology

Tropical oceans are known for being low in nutrients, yet they support incredibly diverse and thriving reef ecosystems created by symbiotic cnidarians such as corals and anemones. This intriguing contradiction, referred to as the Darwin Paradox, has fascinated scientists ever since Charles Darwin first described it in 1842.

A group of researchers from KAUST conducted a study on sea anemones called Aiptasia. They found out that Aiptasia uses the sugar it gets from its partners to recycle waste in its body and survive in places where there are not many nutrients.

According to Guoxin Cui, a research scientist who worked on the project with Manuel Aranda, many studies in the past have tried to figure out where the limited nutrients in the ocean come from, especially nitrogen which is rare.

Guoxin Cui explains that some studies about coral have suggested that the partnership between coral and algae creates areas with lots of nutrients. But until now, researchers didn't fully understand how these organisms were able to create such large ecosystems.

Guoxin Cui focused on studying the relationship between the two organisms at the tissue level. Cnidarians have a simple tissue structure that has two main cell layers - the gastrodermis and the epidermis. Only the inner layer, the gastrodermis, has a relationship with algae inside the cells.

The team used a special technique called laser microdissection to separate the two tissue layers of Aiptasia and study how different genes were being expressed in each layer. They then used a new technology called single-cell RNA-sequencing to study the RNA transcription profiles associated with the partnership at a very small cellular level. This is the first time these techniques have been used to study the relationship between organisms in sea anemones.

The approach allowed the researchers to identify the key transporters involved in nitrogen assimilation, before using antibody staining to track the localization of these nutrient transporters within the anemone.

Manuel Aranda explains that the team found that the sea anemone changes the way it transports nutrients after it receives glucose from its symbionts. This allows it to distribute glucose to all of its tissues. Additionally, the sea anemone uses most of its body to recycle nitrogen waste that it produces and processes any ammonium available in the environment.

Guoxin Cui explains that the symbiotic relationship between the sea anemone and its symbionts turns the entire organism into a nitrogen assimilator. This challenges the belief that only the algae are responsible for nitrogen assimilation and recycling in this relationship. Both organisms work together as a single unit, creating a unique and inseparable partnership.

The research team hopes that their study will serve as a foundation for developing more effective selective breeding methods and will provide insight into efforts to protect reef ecosystems. They are planning to expand their research to explore the symbiotic relationships in various cnidarian taxa and ecological contexts beyond what was studied in this research.

Published in journalScience Advances

Source/CreditKing Abdullah University of Science and Technology

Reference Number: es051523_01

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