Mechanistic insight into immune control of cnidarian endosymbiosis

Algae live inside corals and transfer valuable nutrients to them. This essential endosymbiotic relationship is the foundation of reef ecosystems.

Elevated temperature, as a consequence of climate change, disrupts this symbiosis, resulting in the expulsion of algae, coral bleaching, and eventual reef destruction. Symbiosis establishment and bleaching significantly alters the expression of numerous host immune genes. This suggests that coral immunity regulates symbiosis, but the mechanisms remain elusive.

I aim to understand the role of host immunity in coral-algal symbiosis using anemones as a model.

In my host laboratory, we were able to generate immune mutants and transgenic lines to monitor distinct stages of symbiosis.

Taking advantage of these lines, and the molecular tools established in the host laboratory such as quantitative phagocytosis assays, fluorescence microscopy, and transcriptomics, I will functionally determine how immunity regulates symbiosis.

I will assay how immune activation and genetic mutation impacts symbiont uptake by anemone larvae, as this is the first step in symbiosis establishment. Subsequently, I will perform RNA sequencing to determine genes downstream of immunity that control symbiont uptake.

Second, I will compare bleaching rates in anemones upon immune activation in both wild-type and immune mutants, perform RNA sequencing and identify genes altered in mutants to elucidate mechanisms of immune control of bleaching.

Third, I will do comparative coral fieldwork to determine whether immune stimulation and mutation alters symbiosis establishment and bleaching in corals from their natural environment.

Using novel functional tools this project will provide new insight into how evolutionarily ancient innate immune pathways have been co-opted to regulate coral symbiosis in health and what goes awry under environmental stress, providing valuable information to guide restoration efforts.