Generation of clade- and symbiont-specific antibodies to characterize marker molecules during Cnidaria-Symbiodinium endosymbiosis

Abstract

The endosymbiosis between cnidarians and dinoflagellates is responsible for the formation of coral reefs. Changes in molecules have been identified during the process of cnidaria-Symbiodinium endosymbiosis. However, the complexity of the molecular interaction has prevented the establishment of a mechanistic explanation of cellular regulation in this mutualistic symbiosis. To date, no marker molecules have been identified to specifically represent the symbiotic status. Because the endosymbiotic association occurs in the symbiotic gastrodermal cells (SGCs), whole cells of isolated SGCs were used as an antigen to generate monoclonal antibodies (mAb) to screen possible molecular candidates of symbiotic markers. The results showed that one of the generated monoclonal antibodies, 2–6F, specifically recognized clade C symbiotic Symbiodinium but not its free-living counterpart or other Symbiodinium clades. The expression levels of 2–6F mAb-recognized proteins are highly correlated with the symbiotic status, and these proteins were characterized as N-linked glycoproteins via treatment with peptide N-glycosidase F. Furthermore, their glycan moieties were markedly different from those of free-living Symbiodinium, potentially suggesting host regulation of post-translational modification. Consequently, the 2–6F mAb can be used to detect the symbiotic state of corals and investigate the complex molecular interactions in cnidaria-Symbiodinium endosymbiosis.

Global Shifts in Gene Expression Profiles Accompanied with Environmental Changes in Cnidarian-Dinoflagellate Endosymbiosis

“…The other encodes a sucrose-phosphate synthase family protein SPS4 , which might be related to photosynthetic sucrose synthesis. In the cnidarian-algal symbiosis, it is suggested that sugar, more specifically glucose, is an important component for not only the supply of photosynthesized carbohydrates from symbiont to host (Burriesci et al 2012) but also for the recognition of symbionts by the host (Takeuchi et al 2017; Huang et al 2017). Our results raise a possibility that cytosolic sugar metabolism and Golgi apparatus-mediated glycosylation of proteins and/or cell wall components may be susceptible to stress and damage when symbionts are exposed to heat in hospite (Figure 5).…”

“…Previous studies suggested that lectin proteins capable of binding the glucose moiety might be involved in the recognition of Symbiodiniaceae symbionts by the host coral Acropora tenuis (Takeuchi et al 2017). Furthermore, a glycoprotein was characterized as the first Symbiodiniaceae protein and was localized at the cell surface, expressed exclusively when the symbiont was colonized within the host (Huang et al 2017). In the HIB process, the altered transport rate of degraded metabolites to the host cytosol may work as a negative feedback signal for the subsequent decrease of metabolite flow (Davy et al 2012).…”

A New Method for Collecting Large Amounts of Symbiotic Gastrodermal Cells from Octocorals

“…In our previous works, we successfully isolated SGCs from E. glabrescens and studied the endosymbiosis relationship between stony corals and dinoflagellates [6,12,14]. We now wanted to establish a new model system using octocorals as an animal model to study the endosymbiotic relationship between octocorals and dinoflagellates.…”

“…Furthermore, we used SGCs as an antigen to generate antibodies and produced a new monoclonal antibody that specifically recognizes clade C (now renamed Cladocopium) [13] symbionts, but not their free-living counterparts or other Symbiodiniacea. The monoclonal proteins recognizable by the antibody are symbiotic markers for Cladocopium symbionts, whose expression levels vary depending on the health status of corals [14]. Accordingly, SGC membranes may regulate the stability of the host coral and dinoflagellates.…”