Evidence that glucose is the major transferred metabolite in dinoflagellate–cnidarian symbiosis

Abstract

SUMMARYReef-building corals and many other cnidarians are symbiotic with dinoflagellates of the genus Symbiodinium. It has long been known that the endosymbiotic algae transfer much of their photosynthetically fixed carbon to the host and that this can provide much of the hostʼs total energy. However, it has remained unclear which metabolite(s) are directly translocated from the algae into the host tissue. We reexamined this question in the small sea anemone Aiptasia using labeling of intact animals in the light with 13 C-bicarbonate, rapid homogenization and separation of animal and algal fractions, and analysis of metabolite labeling by gas chromatography-mass spectrometry. We found labeled glucose in the animal fraction within 2min of exposure to 13 C-bicarbonate, whereas no significant labeling of other compounds was observed within the first 10min. Although considerable previous evidence has suggested that glycerol might be a major translocated metabolite, we saw no significant labeling of glycerol within the first hour, and incubation of intact animals with 13 C-labeled glycerol did not result in a rapid production of 13 C-glucose. In contrast, when Symbiodinium cells freshly isolated from host tissue were exposed to light and 13 C-bicarbonate in the presence of host homogenate, labeled glycerol, but not glucose, was detected in the medium. We also observed early production of labeled glucose, but not glycerol, in three coral species. Taken together, the results suggest that glucose is the major translocated metabolite in dinoflagellate-cnidarian symbiosis and that the release of glycerol from isolated algae may be part of a stress response. Supplementary material available online at

The cell specificity of gene expression in the response to heat stress in corals

“…In addition, glucose has been reported as the dominant metabolite transferred between Symbiodinium spp. and the coral host cell (Burriesci et al, 2012). Glucose phosphorylation and the GPCR system are needed for the synthesis of cAMP (Rolland et al, 2001), an important component in cell proliferation of Symbiodinium spp.…”

Marine Invertebrate Larvae Associated with Symbiodinium: A Mutualism from the Start?

“…The host supplies the symbiont with CO 2 and other compounds for cellular synthesis such as nitrogen and phosphorus (Trench, 1979;Allemand et al, 1998;Leggat et al, 2003;Weis et al, 2008). In turn, the symbiont supplies the host with more than 90% of its metabolic requirement, in the form of organic compounds including glucose, glycerol, fatty acids, and amino acids (Muscatine, 1990;Grant et al, 1997;Papina et al, 2003;Burriesci et al, 2012). Still, very little is known about the metabolite exchange between Symbiodinium and metazoan larvae.…”

Symbiont type influences trophic plasticity of a model cnidarian–dinoflagellate symbiosis

“…Anemones consisted of a monoclonal line of aposymbiotic (Burriesci et al, 2012) A. pallida (clone CC7) ( provided by J. Pringle, Stanford University, USA). Aposymbiotic anemones were kept in constant darkness over 2 years in a closed system containing filtered seawater (FSW, 1 µm) and fed brine shrimp weekly.…”