Estrogenicity of Compounds Produced by Anemones and their Algal Symbionts

PAC Gym

Many cnidarians form a symbiotic relationship with intracellular, photosynthetic algae, whereby host and symbiont exchange nutrients and other vital compounds. We believe that this relationship extends beyond nutritive benefits and that the algae influence the development of their hosts. For example, we previously demonstrated that symbiotic anemones, which harbor symbionts, develop larger gonads than aposymbiotic anemones, which lack symbionts. The mechanism underlying this pattern is unknown. Free floating photosynthetic algae, like more complex plants, have been shown to produce organic compounds such as sterols, saponins, and alkaloids, and many of these compounds agonize metazoan nuclear receptors (NR). Furthermore, NR agonists are bioactive in cnidarians, as treatment with estrogenic compounds increases the rate of asexual reproduction in both anthozoans and hydrozoans. We propose that symbiotic algae influence the development and reproduction of host cnidarians via such NR-mediated signaling pathways. We tested this hypothesis using Aiptasia pallida anemones. Our goal was to screen anemone tissue, algal tissue, and anemone culture water for estrogenic NR agonists using a competitive estrogen receptor (ER) binding assay. The assay leveraged three isoforms of teleost estrogen receptors (ER?, ER?1, and ER?2). We detected estrogenic compounds in multiple sample types. These results will be discussed in a physiological context.