Meeting Abstract

P1.39  Thursday, Jan. 3  Differential Labeling of a Secreted Mucilage Component Among and Within Clades of Zooxanthellae MAZZILLO, M.J.*; KEMPF, S.C.; Auburn University; Auburn University mazzimj@auburn.edu

Zooxanthellae (genus: Symbiodinium) are endosymbionts that reside within the tissues of many cnidarians. In this mutualistic relationship the endosymbiotic algae donate photosynthetic products to their host cnidarians in exchange for shelter and nutrients. Past research has demonstrated that Symbiodinium produce mucilage that surrounds the cells while within the symbiosome and also as free-living, encysted dinoflagellates. Symbiodinium is a diverse genus that is divided into at least 8 clades. While the symbiont-host specificity of these clades is just beginning to be understood, the importance of mucilage production in the symbiosis has not yet been examined. Cultured Symbiodinium from different clades were labeled with a previously developed primary antibody that binds to a mucilage component (PC3) of zooxanthellae associated with Aiptasia pallida. Labeling was visualized using secondary antibody conjugated with a fluorescent dye. Labeled zooxanthellae were examined with a confocal microscope to detect differences in labeling between and within clades. Mucilage was found to contain PC3 antigen in cultured zooxanthellae from clades A and B that were originally isolated from Aiptasia pallida. The algae from clades C, D, and H isolated from a variety of other hosts, did not exhibit labeling of the PC3 antigen. Interestingly, algae from clade A zooxanthellae isolated from Zoanthus sociatus also did not label with the PC3 antibody. Thus, in addition to differences seen among clades, there is also intraclade variation in the secretion of this antigen. This could be related to host-symbiont specificity. Future work will look at the structure of PC3 antigen and its possible involvement in establishing specificity between symbiotic partners.