During the project, we investigated distinct aspects of the molecular mechanisms underlying coral symbiosis. We identifies integrins as key molecules for symbiont uptake by the host cell (Jones et al., in prep). We found that immune suppression in the host cell is key for the symbionts to avoid expulsion by 'vomocytosis', and thus stable symbiont intracellurization (Jacobovitz & Rupp et al., Nature Microbiology 2021). We determined that the highly conserved mTOR signalling pathway is co-opted to integrate symbiont derived nutrients into the host cell (Voss et al., Current Biology, 2023). We also identified sterols as key nutrients transferred from symbionts to host. To allow that, the NPC2 gene family has been expanded in symbiotic cnidarians (Hambleton et al., eLife, 2019). Taken together, using our novel model systems' approach to dissect the cell biology of coral-algal endosymbiosis, we made important contributions to a mechanistic understanding of this important symbiotic interaction which is the foundation to coral reef ecosystems. This provides the basis to understand the ecology and evolution of coral symbiosis, a prerequisite to guide reef conservation. Due to our major contributions to the field, we were invited to write a comprehensive review on this topic entitled "Unlocking the Complex Cell Biology of Coral–Dinoflagellate Symbiosis: A Model Systems Approach" (Jacobovitz, Hambleton and Guse; Annual Review of Genetics, in press).
Along the way we also developed various new techniques, protocol and molecular tools to further establish Aiptasia as a model system for the cell biology, ecology and evolution of coral symbiosis. Specifically, we developed a protocol for microinjection to deliver mRNA, protein and DNA to Aiptasia larvae (Jones et al., Scientific Reports 2018), symbiont transformation (Gornik et al, Frontiers in Marine Science, 2022) and larval settlement to close the Aiptasia life cycle (Maegele et al., PNAS, in press). These methods are key to pave the way for a functional analysis of coral symbiosis looking at both partners, cnidarian host and dinoflagellate symbiont.
Finally, we engaged in some side projects during the course of SYMCELLS that are tangential to our analysis of symbiosis and cover the topic of the mechanisms of light sensing in symbiotic cnidarians and its function for adapting to challenging environments (Gornik et al., Molecular Biology and Evolution, 2020 and Kishimoto et al., Scientific Reports, in revision) and a comparative analysis on nutrient allocation in anemones, Garshall et al., bioRxiv doi: 10.1101/2023.05.15.540851).
