Corals are fascinating and beautiful creatures. It’s also a fairly safe bet that most everyone would agree with that statement, judging from the millions of tourists and visitors to our world’s most famous coral reefs every year, and the billions in generated revenue those reefs provide to the countries which claim them. Coral reefs teem with abundant life, abundant colors (even ones in ranges which our poor eyes need help seeing), and abundant energy. These tiny Cnidarians, distant cousins of anemones and jelly fish, form the framework for some of the largest ecosystems on our planet with often as much or more diversification as a tropical jungle.

Yet, just as humans are integrally dependent on the bacteria that reside within us to survive, coral are just as dependent on a tiny algea called Symbiodinium. Symbiodinium comprise a large group of dinoflagellates, which is a group of marine, photosynthetic eukaryotes that includes algaes, protists and plankton. They become engulfed by the coral endoderm where they live on in a symbiotic relationship, providing photosynthetic nutrition in exchange for inorganic molecules they could not otherwise get. The system works amazingly well, but though studied extensively, is still quite mysterious. Even more important, our coral reefs are faced with various destructive dilemmas such as polluted or warming oceans, physical damage from the bottom scraping of fishing ships, carelessness of tourists…the list goes on. Warming trends have been known to cause a problem called “coral bleaching”. This bleaching is caused by a disassociation of the corals and Symbiodinium or a loss of chlorophyll within the algae. Bleaching also causes a host of other problems for the coral, increased disease, declined calcification, etc. that spells destruction for the ecosystem. Because of these problems, scientists are keen to better understand the relationship between host and symbiont.

Enter a group from the National Sun Yat-Sen University in Taiwan, under Chii-Shiarng Chen, who are delving into the protein interactions of these two organisms. They are studying the symbiotic gastrodermal cells (SGCs) which play an integral role in the association of the Symbiodinium and the coral endoderm. Using a similar approach to my blog story from last week, they harvested SGCs from amputated coral tentacles and utilized the biotin-streptavidin interaction to label the SGCs with biotin and later label the biotin with a green fluorescent streptavidin for confocal imaging. Further purification of the surface membrane proteins allowed for 2-D electrophoresis and LC-MS analysis which allowed them to distinguish 44 protein spots on the 2-D gel and identify 19 of the proteins through the LC-MS as molecular chaperons, actin filaments, involved in energy production or miscellaneous cellular functions!

While these results don’t explain the process of the symbiotic relationship between coral and Symbiodinium, it does begin to illuminate the players in the protein interactions that make the relationship work. With that background, Chen’s group (or other groups) can continue to blast away at this interaction, and by understanding, perhaps prevent more damage from occurring on one of the most marvelous and dynamic ecosystems our world has to offer.

Li, H. H., Huang, Z. Y., Ye, S. P., Lu, C. Y., Cheng, P. C., Chen, S. H., & Chen, C. S. (2014). Membrane Labeling of Coral Gastrodermal Cells by Biotinylation: The Proteomic Identification of Surface Proteins Involving Cnidaria-Dinoflagellate Endosymbiosis. PloS one, 9(1), e85119.

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