NSF Award
2422307
One of the most dramatic examples of climate change is the bleaching of coral reefs worldwide. Many corals harbor photosynthetic dinoflagellate algae inside their gut cells giving them a brown color. Coral bleaching is caused by the breakdown of this symbiotic relationship and photosynthetic dinoflagellate algae are either expelled or voluntarily leave the safety of coral host cells. Host cells benefit from the symbiont photosynthate (food) but host cells have to make decisions on which symbiont cells can live inside their own cells and which cannot (self-nonself recognition). Corals are endangered and difficult to work on in the lab, so the researchers have developed an experimental model for coral bleaching, the upside-down jellyfish Cassiopea xamachana. Cassiopea is an ideal system to explore the concept and maintenance of self-nonself relationships during the establishment of stable photosymbiosis because their gut cells take up the same algae that corals do, and Cassiopea can be easily raised in the lab throughout their entire life cycle. This project uses optical imaging and single cell sequencing to follow the cellular and molecular responses of both host and symbiont in the establishment of stable symbiosis. Of particular interest is how the symbiont molecularly ‘hijacks’ the host innate immune system to avoid intracellular digestion. Gene regulatory networks for both host and symbiont will be generated at time points spanning the initiation and generation of stable symbiosis in both ‘good’ algae, and nonsymbiotic cells. This work provides molecular and cell biological insight in to how to rebuild healthy coral reefs. The results from this work will be incorporated into the education and outreach program and provide insight into how to rescue coral reefs in the wild.<br/><br/>One fundamental challenge in biology is to understand how novel cell types arise and how the this leads to the evolution of biological complexity. EcoEvoDevo is the field that embraces how environmental influences- including symbiosis- affect developmental processes. This project investigates the environmental induction of a novel cell type, the amoebocyte, by a photosynthetic dinoflagellate algae during the development of the upside-down jellyfish, Cassiopea xamachana. Amoebocytes arise from Cassiopea gut cells that phagocytose an appropriate species of dinoflagellate to set up a stable intracellular photosymbiosis, withdraw from the endodermal gut epithelium and adopt a mesenchymal phenotype in the mesoglea. Amoebocytes form only after stable photosymbiosis have been established, and their presence is required to complete the Cassiopea life cycle. The upside-down jellyfish, Cassiopea xamachana is an ideal system to explore the concept and maintenance of self-nonself relationships during the establishment of stable photosymbiosis and the environmental induction of a novel cell type, the amoebocyte. Cassiopea has several favorable properties over all other cnidarian photosymbiotic models including the ability to complete the life cycle in the lab, procure ample embryological material daily, quantify symbiont growth rates, outstanding genomic resources and favorable optical properties. This work will use FACS sorting, Next Generation sequencing, and lightsheet microscopy approaches with fine time scales to generate gene regulatory networks for both host and symbiont during successful and unsuccessful host-alga interactions.<br/><br/>This award was co-funded by Symbiosis, Infection, and Immunity (SII) and Plant, Fungal, and Microbial Development (PFuMiD) programs in BIO-IOS.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
