Characterizing the NF-κB pathway of the innate immune system in the sea anemone Exaiptasia pallida

Coral reefs are unique and globally important ecosystems that provide vital services to marine life as well as to human health and the economy. The survival of the reef ecosystem is based upon an endosymbiotic relationship between the coral and a photosynthetic microalgae of the family Symbiodiniaceae that inhabit the coral cells. The present study incorporates the use of a model organism for the Symbiodiniaceae-cnidarian symbiosis—Exaiptasia pallida—and cell biology methodology to characterize a specific pathway of the immune system hypothesized to play a key role in symbiosis: the NF-κB pathway. I identify three proteins, Aiptasia IκBcl3-A, IκBcl3-B, and IκBcl3-C, as homologs for either IκB or Bcl3 proteins within the Aiptasia NF-κB pathway. Through sequence and conserved domain analysis as well as characterization of protein-protein interactions, I propose a novel pathway of NF-κB induction in which IκBcl3-A may act as an IκBα homolog in complex with IκBcl3-C, as well as a Bcl3 homolog along with IκBcl3-B. The molecular characterization presented in this study provides targets for genetic manipulations aimed at studying the regulatory roles that particular proteins play in cnidarian symbiosis and immunity