Effects of lectin in the scleractinian coral Ctenactis echinata on symbiotic zooxanthellae

Abstract

We report herein the presence of a lectin in the scleractinian coral Ctenactis (Fungia) echinata. The lectin bound preferentially to lactose, melibiose, and D-galactose. The purified lectin CecL was composed of several isolectins, and it was found to have a molecular mass of 67.4 kDa via gel filtration. Glycopeptidase F-treated CecL showed a single band at 32.5 kDa. The mass/charge ratios of the reduced CecL peaks were equivalent to half those of the native peaks. These results suggest that CecL is composed of two glycosylated polypeptides linked by interchain disulfide bonds. In a biological activity test using a zooxanthellal culture (Dinoflagellate Symbiodinium) clonally isolated from Fungia cf. fungites, CecL transformed the flagellated motile form of Symbiodinium into the nonmotile coccoid form, a form equivalent to the symbiotic stage. The activity of CecL on Symbiodinium cells was concentration dependent, and 100 lg/ml CecL arrested Symbiodinium cells in the coccoid form for 5 days. CecL also suppressed the growth of Symbiodinium cells, unlike the octocoral lectin derived from Sinularia lochmodes, which arrests Symbiodinium cells in the coccoid form but does not affect the growth of the coccoid. This result provides further evidence that coral lectins play a role in symbiont engagement and maintenance in zooxanthellaecoral symbiosis.

Biology of Symbiotic Dinoflagellates (Symbiodinium) in Corals

“…These results suggest that glycoconjugates on the Symbiodinium cell surface are the key ligand through which the lectin induces morphological transformation. Similar mechanisms have also been found in scleractinian corals (Wood-Charlson et al 2006 ;Jimbo et al 2010 ). Not only important in the initial infection, lectins might be involved in maintaining the symbionts and so a breakdown of this function leads to coral breaching.…”

Cell Biology of Cnidarian-Dinoflagellate Symbiosis

“…A D-galactose-binding lectin, SLL-2, was purified from the octocoral Sinularia lochomodes, sequenced, and found by immunolocalization to occur surrounding symbiotic dinoflagellates in the gastrodermis (174,175). Another galactose-binding lectin, CecL, from the coral Ctenactis echinata has also recently been described (176). Two lectins with CTLDs specific for mannose have been identified from corals: millectin from Acropora millepora (191,192) and PdC lectin from Pocillopora damicornis (385).…”

Squishy lipids: Temperature effects on the betaine and galactolipid profiles of a C18/C18 peridinin‐containing dinoflagellate, Symbiodinium microadriaticum (Dinophyceae), isolated from the mangrove jellyfish, Cassiopea xamachana

“…; Jimbo et al . ). Hosts can expel these symbionts if there is an excess number found inside the host (Maruyama & Heslinga ; Baghdasarian & Muscatine ; Hirose et al .…”

“…Harii et al 2010). However, Symbiodinium species do not need to initiate an association with a cnidarian to survive (Hirose et al 2008;Littman et al 2008;Jimbo et al 2010). Hosts can expel these symbionts if there is an excess number found inside the host (Maruyama & Heslinga 1997;Baghdasarian & Muscatine 2000;Hirose et al 2008), and/or if predators consuming symbiotic hosts cause an expulsion of Symbiodinium (Bachman & Muller-Parker 2007;Pochon et al 2010).…”