RODRIGUEZ-LANETTY, Mauricio*; WEIS , Virginia M; PHILLIPS, Wendy S; Oregon State University: Transcriptome analysis of a cnidarian � dinoflagellate mutualism reveals complex modulation of host gene expression

Cnidarian � dinoflagellate endosymbioses are one of the most important mutualisms in the marine environment. They form the trophic and structural foundation of coral reef ecosystems. Despite the prevalence of these symbioses, we still know very little about the cellular and molecular basis of the symbiosis. Through a comparative transcriptome analysis, we detected statistically significant differences in host gene expression profiles between sea anemones in a symbiotic and non-symbiotic state. The group of genes whose expression is altered is diverse, suggesting that the molecular regulation of the symbiosis is governed by changes in multiple cellular processes. Our data do not support the existence of symbiosis-specific genes involved in controlling and regulating the symbiosis. Instead, it appears that the symbiosis is maintained by altering expression of existing genes involved in vital cellular processes. In the context of cnidarian � dinoflagellate symbioses, we discuss pivotal host gene expression changes involved in lipid metabolism, cell adhesion, cell proliferation, apoptosis, and oxidative stress. Specifically, the finding of key genes involved in cell cycle progression and apoptosis have led us to hypothesize that a suppression of apoptosis, together with a deregulation of the host cell cycle, create a platform that might be necessary for symbiont and/or symbiont-containing host cell survival. This first comprehensive molecular examination of the cnidarian � dinoflagellate associations provides critical insight into the maintenance and regulation of the symbiosis.