Coral reefs are important ecosystems, both ecologically and economically. They are home to a vast variety of marine creatures, but they also have immense value in protecting coastlines from erosion and damage. To survive in nutrient-poor habitats, coral reefs depend on intracellular symbiosis with photosynthetic dinoflagellate algae that are acquired via phagocytosis. Interestingly, and unlike the evolutionary related purpose of phagocytosis for pathogen clearance, these symbionts provide nutrients to their hosts – a reason why they might persist intracellularly rather than being destroyed by the host.
“About 75 percent of corals produce non-symbiotic offspring,” explains Dr. Annika Guse, group leader at the Center for Organismal Studies (COS) at Heidelberg University. She and her team want to understand the underlying molecular mechanisms of symbiosis establishment. But “studying corals in a lab is immensely difficult”, she says. “They grow very slowly and sexual reproduction only occurs once a year, which gives us hardly any material to work with under controlled laboratory conditions and on a quantitative basis.” To overcome these limitations, Annika Guse and her team adopted the marine sea anemone Aiptasia as a primary lab model. Like corals, Aiptasia produces larvae without symbionts and lives in a stable, mutualistic symbiosis with the same types of dinoflagellates as corals; however, the organism can be easily kept and sexual reproduction can be induced under laboratory conditions, which allows the team unlimited access to new larvae for experimentation.
Dr. Annika Guse (top left) is one of five Heidelberg scientists to receive an ERC Consolidator Grant this year. (top right: symbiotic larva, bottom left: intracellular symbionts). Fotos: Guselab
In her ERC-granted research, Annika Guse will focus on two fundamental aspects of coral-algae symbiosis: she will investigate the cellular mechanisms of symbiotic acquisition and integration as well as uncover major aspects of metabolic dependence, i.e. the transfer of cholesterol and sterols from the symbiont to the host. “Corals are unable to synthesize cholesterol, and previous research suggests that corals may depend on symbiont-derived sterols as key nutrients for cellular function” Guse adds. “My background in molecular cell biology, biochemistry, and microscopy allows us to provide a completely new approach to understand coral-algal symbiosis, building a bridge between modern cell biology and ecology.”
Annika Guse’s unique expertise, together with the imminent environmental dangers coral reefs face due to elevated sea temperatures and pollution have contributed to her securing the ERC Consolidator Grant – congratulations! Her results will hopefully shed more light on the mechanisms underlying this extremely sensitive and endangered ecosystem.
Dr. Annika Guse
Centre for Organismal Studies
Im Neuenheimer Feld 230
Tel. + 49 6221-54 6264