Dr. Phillip Cleves, The Carnegie Institution for Science, Washington D.C.
Dr. Phillip Cleves, Principal Investigator in the Department of Embryology at the Carnegie Institution, will present his talk: "Molecular and cellular bases of coral symbiosis and its breakdown".
The symbiosis between corals and dinoflagellate algae is essential to the energetic requirements of coral-reef ecosystems. However, coral reefs are in danger due to elevated ocean temperatures and other stressors that lead to the breakdown of this symbiosis in a process called "coral bleaching." Despite the importance of coral reefs, the molecular and cellular basis of how corals maintain a healthy symbiosis and avoid bleaching is poorly understood, in part because of the lack of tractable genetic model systems. My lab has been focusing on developing genetic tools in several symbiotic cnidarians to allow rigorous functional testing of candidate genes and pathways. One side of my lab uses the small anemone Aiptasia, which is symbiotic with similar algal strains to those found in reef-building corals, as an experimentally tractable model for coral symbiosis and bleaching. To explore the transcriptional basis of heat-induced bleaching, we used RNAseq to identify genes that are differentially expressed during heat stress of symbiotic and aposymbiotic Aiptasia. These experiments have allowed us to identify genes and pathways that we hypothesize underlie the cell biology of the symbiosis and the physiological process of bleaching. Excitingly, we have recently developed methods to overexpress, knockdown, and knockout genes in Aiptasia, allowing us to test these hypotheses for the first time.
While we are progressing in understanding symbiosis and bleaching mechanisms in Aiptasia, we want to compare these mechanisms to ecologically important reef-building corals. To this end, we have successfully used the CRISPR/Cas9 technology to create genetic changes in the coral Acropora millepora. We have used this technique to functionally characterize genes that underlie coral heat tolerance and other ecologically important traits. However, the once-a-year access to embryos dictated by natural spawning events limits our ability to rapidly study gene function in reef-building corals. To solve this issue, we have combined novel methods to spawn corals in the lab with our CRISPR/Cas9 methods to generate a genetically tractable coral model system. Using this approach, we can generate genetically modified coral lines to study mechanisms of symbiosis and bleaching throughout the year. Our long-term goal is to gain critical molecular insights into how corals may adapt to climate change to inform their conservation. Finally, by comparing Aiptasia and corals, we also hope to gain insights into how symbioses and heat tolerance evolve.