The molecular basis of metabolic interactions in cnidarian symbioses 
By Dr. Guoxin Cui
Senior Research Scientist 
King Abdullah University of Science and Technology (KAUST) 
Saudi Arabia
 
Date:              24 February 2025 (Monday)
Time:             4 pm – 5 pm 
Venue:          Room 2405 (Lift 17 - 18)
 
Abstract:
Coral reefs represent a paradox of nature—flourishing in nutrient-poor waters while sustaining immense biodiversity. Their success hinges on a delicate symbiosis between reef-building corals and photosynthetic dinoflagellates of the Symbiodiniaceae family. This metabolic partnership fuels coral growth and reef formation, yet it is remarkably sensitive to environmental fluctuations. Climate change, pollution, and ocean acidification increasingly disrupt this balance, leading to widespread bleaching and reef collapse. To understand both the resilience and fragility of these ecosystems, it is essential to unravel the molecular mechanisms that underpin symbiont regulation, nutrient exchange, and evolutionary adaptation.

Our research has uncovered a fundamental carbon-nitrogen negative feedback loop that regulates symbiont proliferation across independently evolved cnidarian hosts. At the heart of this mechanism lies the host’s ability to control nitrogen availability through glutamine synthetase-glutamate synthase mediated nitrogen assimilation, a process that restricts symbiont growth in response to shifting carbon supply. The intricate metabolic crosstalk between partners not only governs symbiont density but also shapes symbiont life history, keeping them in a non-motile, nitrogen-limited state within the host. This dynamic regulation extends beyond corals and is deeply conserved across diverse cnidarians, providing a compelling explanation for the repeated evolution of these symbiotic relationships. Further, by elucidating host-driven nitrogen recycling, we highlight how corals actively manage internal nutrient fluxes, fine-tuning their metabolic interactions to sustain symbiosis under fluctuating environmental conditions.

Together, our work presents a unifying framework for understanding how corals have thrived in oligotrophic seas for millions of years, yet also exposes the metabolic vulnerabilities that make them highly susceptible to environmental stress. By integrating molecular biology, metabolism, and evolutionary ecology, my research offers critical insights into the mechanisms that both sustain and endanger the world’s coral reef ecosystems. 
 
Biography:
Guoxin Cui is a Senior Research Scientist at King Abdullah University of Science and Technology (KAUST) in Saudi Arabia. He earned his Ph.D. in 2018 from KAUST, focusing on the metabolic interactions in the Aiptasia–Symbiodiniaceae symbiosis. Over the years, he has expanded his research to explore the molecular underpinnings of diverse cnidarian symbioses, blending his expertise in molecular biology, genomics, epigenomics, single-cell sequencing, and spatial omics.

He is deeply committed to understanding the intricate dialogue between cnidarian hosts and their dinoflagellate endosymbionts—an association that forms the cornerstone of coral reef ecosystems. Through cutting-edge multi-omics and cell biology approaches, Dr. Cui investigates how these complex interactions are regulated, uncovering the cellular processes and nutrient dynamics that enable these partnerships to thrive in typical nutrient-poor ocean environments.

Dr. Cui’s work is particularly timely, given the escalating threats posed by climate change to marine biodiversity. His research not only advances our fundamental understanding of symbiosis but also provides vital insights for developing strategies aimed at coral reef restoration and the conservation of marine ecosystems. 
 

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