Imaging reveals the molecular process used to control the subcellular environment of algal symbionts by corals

Researchers at UC San Diego’s Scripps Institution of Oceanography found a novel molecular mechanism corals use to control their subcellular environment.

A specialized protein controls the fluctuations in the day-to-night carbon dioxide and nitrogen transfer through coral’s cell membranes to the alga. This is crucial because coral and algae live together in a mutually beneficial relationship known as symbiosis. Although they expected to find the protein, the team could not have anticipated the day-today changes in intracellular areas they observed.

“We show the interface between the animal hosts, and the plants that reside inside them, is a dynamically managed microenvironment,” said Angus Thies. Thies is a doctoral candidate who works in Scripps Oceanography marine physiologist Martin Tresguerres. Thies and his coauthors (including scientists from the University of Manitoba in Canada) describe the first direct observations of cellular interaction between corals and symbiotic algae in the March 11 edition of Science Advances. The National Science Foundation (NSF), through a grant for Tresguerres as well as a fellowship for Thies, supported this study.

The findings reported in Science AdvancesIt would have been almost impossible to get. Tresguerres’s team had spent years researching how to best prepare corals for microscopy research. The team acquired a machine known as a laser confocal SUPER-resolution system, which was funded by the Arthur M. & Kate E. Tode Research Endowment Marine Biological Sciences at UC San Diego. This was what sealed the deal.

This system allowed the team the ability to image the coral membrane around the algae with a resolution greater than that of the lab’s previous microscope. The new system can distinguish features within 120 nanometers. A human hair is 90,000 nanometers thick.

Tresguerres stated that decades of research has shown corals regulate the amount of nitrogen they give their algae. The problem is that the algae may grow and multiply too fast if they receive too much nitrogen. This could disrupt the symbiosis.

Like humans, coral health can be monitored down to the cellular level. Coral thrives when everything is working at the cellular level. When things go wrong, it often leads to malfunction or disease, possibly including ‘bleaching. The symbiosis interface, also known as the “symbiosis interface”, is perhaps the most important interface on the entire reef.

Martin Tresguerres Scripps Oceanography Marine Physiologist

Symbioses are important biological interactions in many living organisms. For example, the bacteria in our digestive system and humans are in a symbiotic partnership. But there is a difference.

“Bacteria can live in our cells, but not in our cells,” Thies said. Thies stated that corals have these algae living inside the cells of their host animals. It’s a tight space. It’s like having roommates for life. You want everyone to be happy.

Corals may look like colorful rocks with tiny polyps. Thies stated, “They are in fact, amongst the most important animal on Earth.” Around one billion people rely on coral Reef ecosystems directly or indirectly for their diet, and scientists are still unsure of the function of corals at the cellular level.

The Science AdvancesStudy identified a cell mechanism that mediates nitrogen delivery to the Symbiotic Algae under normal conditions. This is a significant discovery because scientists need to first understand how healthy corals function under normal conditions to understand the consequences of a process going wrong. How is climate change or pollution affecting this process?

Tresguerres stated that “Perhaps, in certain climate conditions, this mechanism can be disrupted and lead to bleaching because algae don’t get enough nitrogen or they have too many.” “That opens up for a lot research, both by ourselves and other labs.”

Thies, who earned his undergraduate degree in marine biology from UC San Diego in 2017, started working on this project while he was a student in Tresguerres’s laboratory. He has been a Scripps Oceanography Doctoral Scholar Fellow Fellow and an NSF Graduate Fellow.

Thies stated that corals are difficult organisms to work alongside. “Corals are complicated symbiotic and require a lot aquarium care. Sometimes they can be difficult to keep happy. A team of six UC San Diego undergraduates and graduate students did just that, earning recognition in the Science AdvancesThey will need paper to support their efforts.

The Tresguerres lab studies many organisms. However, they often find the same organisms in other organisms. Although corals, sharks and algae may share some enzymes, each organism uses them in different ways. Even coral species living at the same depth may have different adaptations.

Tresguerres likens enzymes and proteins to LEGO.^® bricks. Many enzymes are found in corals that support symbiosis. Similar enzymes can be found in an OsedaxThe worm eats whale carcasses and helps it eat bone. Similar enzymes are found in the gills of sharks and stingrays. They help maintain healthy levels of blood acidity.

Tresguerres stated, “I find Evolution fascinating. Especially at the cellular level.” “The proteins are the exact same, but they partner with other proteins, or they’re in different cell compartments and perform a completely different function.”

The research team also included Thies and Tresguerres as well as Alex R. Quijada­Rodriguez, Haonan Ziyao and Prof. Dirk Weihrauch from the University of Manitoba, Canada.