Differential expression of Exaiptasia pallida GIMAP genes upon induction of apoptosis and autophagy suggests a potential role in cnidarian symbiosis and disease

Abstract

Coral reefs, one of the world's most productive and diverse ecosystems, are currently threatened by a variety of stressors that result in increased prevalence of both bleaching and disease. Therefore, understanding the molecular mechanisms involved in these responses is critical to mitigate future damage to the reefs. One group of genes that is potentially involved in cnidarian immunity and symbiosis is GTPases of Immunity Associated Proteins (GIMAP). In vertebrates, this family of proteins is involved in regulating the fate of developing lymphocytes and interacts with proteins involved in apoptosis and autophagy. Since apoptosis, autophagy, and immunity have previously shown to be involved in cnidarian symbiosis and disease, the goal of this research was to determine the role of cnidarian GIMAPs in these processes using the anemone Exaiptasia pallida. To do so, GIMAP genes were characterized in the E. pallida genome and changes in gene expression were measured using qPCR in response to chemical induction of apoptosis, autophagy, and treatment with the immune stimulant lipopolysaccharide (LPS) in both aposymbiotic and symbiotic anemones. The results revealed four GIMAP-like genes in E. pallida, referred to as Ep_GIMAPs. Induction of apoptosis and autophagy resulted in a general downregulation of Ep_GIMAPs, but no significant changes were observed in response to LPS treatment. This indicates Ep_GIMAPs may be involved in regulation of apoptosis and autophagy, and therefore could play a role in cnidarian-dinoflagellate symbiosis. Overall, these results increase our knowledge on the function of GIMAPs in a basal metazoan.