Meeting Abstract
Despite its central importance for coral-reef ecosystems, the cnidarian-dinoflagellate symbiosis remains poorly understood at the genetic, molecular, and cellular levels. To explore the mechanisms underlying this symbiosis and their responses to stress, we used RNA-Seq to identify genes that are differentially expressed under thermal stress, using the small sea anemone Aiptasia as a model system. The clonal stock CC7 (containing a Clade A Symbiodinium symbiont), an aposymbiotic stock derived from CC7, and the stock CC7-SSB01 (aposymbiotic CC7 reinfected with a clonal Clade B Symbiodinium strain) were thermally stressed at 34° at 25 µE (12:12 L:D) and sampled at intervals for 10 d. We observed a strong upregulation in the mRNAs for heat-shock and other stress-response proteins at early time points (0-12 h) but distinct expression patterns when the symbiotic stocks began to bleach (≥48 h). The overall expression patterns were similar in all three stocks, indicating that most, at least, are not related specifically to the presence of the endosymbionts. Further analysis of these expression patterns is in progress. We are also examining how prior thermal history influences the tolerance of symbiotic Aiptasia to subsequent thermal stress, finding that acclimation at elevated but sub-bleaching temperatures (30-32°) decreases the rate and severity of bleaching during subsequent thermal stress at 34°. Future studies will vary the acclimation temperatures and durations and analyze gene expression in thermally acclimated animals, in order to detect genes that influence thermal tolerance.
