Coral reefs are profoundly important ecosystems that are threatened worldwide. Corals are animals that form the structural basis of these reefs, and contain microscopic algae inside their cells. This mutualistic partnership or symbiosis provides the foundation of the entire diverse coral reef ecosystem. While a great deal of attention has been focused on the environmental threats to corals and how and if corals will survive climate change, there remains only a partial understanding of the microscale cellular and molecular mechanisms that underpin the coral-algal symbiosis. Insight into regulation of this symbiosis will provide a stronger foundation for studies of the impact of ocean warming, acidification and other anthropogenic stressors on coral health. This project will bring together a coral biologist , a chemist, and a cancer cell biologist, to examine the intricate molecular and cellular conversations that the partners of the symbiosis engage in to initiate and maintain the symbiosis. The project will also examine how these conversations go awry and lead to symbiosis dysfunction and breakdown during the phenomenon of coral bleaching, a stress response to elevated temperature that results in coral death and reef degradation. In addition to studying corals in the field, this project will also study sea anemones which are an excellent proxy for corals, many of which are endangered and are difficult to culture in a laboratory setting. This project will contribute to the training of scientists and expose school-aged children to coral reef and symbiosis science.
Many cnidarians, including corals and anemones, engage in symbioses with photosynthetic dinoflagellates (Symbiodinium spp.), and together they form the trophic and structural foundation of the coral reef ecosystem. Despite the importance of corals to coral reefs and the threatened state of coral reef health in an era of dramatic climate change, the basic cellular and molecular mechanisms underlying the initiation, establishment and breakdown of the partnership are only partially understood. This project will examine inter-partner signaling and host cell immune response during onset and breakdown of cnidarian-dinoflagellate symbioses. Experiments will be conducted in two model systems, the anemone Aiptasia sp.-Symbiodinium B1 and larvae of the coral Fungia scutaria-Symbiodinium C1f. The team proposes the following Specific Aims: Aim 1: Characterize glycan recognition between host and invading Symbiodinium by glycan profiling and glycome manipulation of the algae, and host receptor pull-down approaches. Aim 2: Compare structural dynamics of phagocytosis and intracellular signaling when hosts are challenged with Symbiodinium by analyzing phagocytic profiles, phagosomal markers, NF-kB activation and the signaling sphingosine rheostat in hosts challenged with different symbiont types and other particles. Aim 3: Examine disruptions and changes in phagosomal dynamics and cell signaling in partnerships subjected to elevated temperature that leads to bleaching by measuring changes in phagosomal maturation, activation of NF-kB and sphingolipid signaling in host tissues after an elevated temperature stress.
