Meeting Abstract
Cnidarians are evolutionarily ancient metazoans, many of which form symbioses with intracellular, photosynthetic algae. It is assumed that this symbiosis primarily confers metabolic benefits to the host, with the organic products of algal photosynthesis donated to the anemone in return for inorganic nutrients. However, symbionts likely modulate host performance in other ways. For example, we recently demonstrated that symbiotic anemones (harboring symbionts) developed larger gonads than aposymbiotic anemones (lacking symbionts). We propose that symbiotic algae produce compounds that modulate the development and reproduction of their cnidarian hosts by acting on nuclear receptors. Like higher plants, free-living algae and cyanobacteria produce compounds including alkaloids, saponins, and flavonoids, many of which bind to nuclear receptors (NRs). Thus, it is likely that compounds from symbiotic algae affect host development and reproduction via such NR-mediated signaling pathways. These pathways presumably evolved early among metazoans. For example, steroids, which bind to NRs in more advanced metazoans, are found in, metabolized by, secreted from, and bioactive in cnidarians. The goal of this particular project was to screen compounds produced by algal symbionts (Symbiodinium spp.) for nuclear receptor (NR) agonism and/or antagonism using a competitive estrogen receptor (ER) binding assay. We also began to explore the mechanisms by which estrogenic compounds may function in cnidarians (specifically Exaiptasia pallida). Our results will be discussed in the context of interspecific cell signaling pathways.
