Meeting Abstract
Lipids play a central in symbiosis, providing both cellular structure and energy storage, but little is known about how signaling lipids participate in onset and breakdown of symbiosis between cnidarians and dinoflagellates of the genus Symbiodinium. Signaling lipids, sphingosine (Sph) and sphingosine-1-phosphate (S1P), play a pivotal role in determining cell fate, where increased Sph drives apoptotic activity within the cell while S1P promotes cell survival. The balance of these lipids creates the ‘sphingosine rheostat’ controlled by enzymatic reactions of sphingosine kinase (SPHK) and sphingosine-1-phosphatase (SPPase). A recent study demonstrated that exogenously applied sphingolipids could alter the cnidarian-dinoflagellate partnership, however endogenous regulation of the rheostat in cnidarians has not been characterized. In this study, we investigated the role of rheostat during symbiont colonization and thermal stress in the sea anemone Aiptasia. During colonization, anemones were inoculated with Symbiodinium and monitored over three days. For thermal stress, anemones were exposed to a range of elevated temperature (27 to 33°C) over one week. Symbiont uptake was quantified with qRT-PCR and symbiont loss measured by fluorescent microscopy. In both treatments, the expression of rheostat enzymes was examined using qRT-PCR. During symbiont colonization, the rheostat shifted toward cell survival with up-regulation of SPHK after 24 hours. Conversely, under hyperthermal stress the rheostat shifted to cell death after 1-2 days of exposure. Finally, to link gene expression to enzymatic activity, we quantified sphingolipid concentrations using mass spectrometry analysis of lipid extracts. Collectively these data suggest that sphingolipid signaling plays a regulatory role in cnidarian-dinoflagellate symbiosis.
