Are NPC2D Protein Levels in Symbiotic Anemones a Function of the Presence of Symbionts or their Photosynthetic Activity?
The sea anemone Aiptasia pallida lives in a mutually beneficial relationship, called symbiosis, with the unicellular algae Symbiodinium. The algae live within the anemones and the photosynthetic products that they produce are a major nutrient source for the host. If stress occurs, however, the algae may begin to leave. Yet, even if the anemone becomes aposymbiotic, that is, without any Symbiodinium, it still can live comparably to a symbiotic anemone if an alternative food source is utilized.
In previous experiments, it has been demonstrated that a gene called NPC2D is expressed 4-600 times more in symbiotic anemones than in aposymbiotic anemones! Furthermore, in our lab, it has been observed that as symbiont number increases, NPC2D protein expression increases. This suggests that the protein may be involved with maintaining symbiosis between the two organisms.
In this set of experiments, we explored whether NPC2D protein expression occurs as a function of the presence of symbionts or as a function of the photosynthetic activity by the symbionts. In order to do this, we inhibited photosynthesis of the symbionts in two different manners: 1) by withholding light exposure or 2) by inhibiting photosynthesis using DCMU, a commercial herbicide. We then isolated total protein from the anemones after 2 hours, 14 hours, 72 hours, and 1 week of exposure and quantified NPC2D protein expression using Western Blotting. Additionally, at each time point, we quantified the symbionts present in the anemones, in order to look at the symbiotic state of each organism.