Isolation of a sulfoquinovosyl monoacylglycerol from Bryopsis sp (chlorophyta): Identification of a factor causing a possible species-specific ecdysis response in Gambierdiscus toxicus (dinophyceae)

A bioactive compound that induced ecdysis (thecal loss) in Gambierdiscus to xicus Adachi et Fukuyo (Dinophyceae) cultures was isolated from a host macr oalga, Bryopsis sp, (Chlorophyta), The ecdysis factor was identified by spe ctroscopic methods as 1-O-palmitoyl-3-O(6'-sulfo-alpha -D-quinovopyranosyl) (PSQG). From our results, PSQG induced ecdysis at a high frequency and app eared not to inhibit the growth of G. toxicus cultures, The induction of ec dysis followed a dose-dependent saturation curve from 4 to 8 muM PSQG. To d etermine specificity of PSQG, the effects of palmitoyl-L-alpha -lysophospha tidylcholine (PLPC) were observed. Because PLPC contains a lipophilic palmi toyl. moiety and hydrophilic phosphatidyl choline group, the compound posse sses a detergent-like amphiphathic property similar to PSQG. Oar results de monstrate that PLPC induced ecdysis at a high frequency in G. toxicus cultu res and generated a similar dose-response curve as PSQG. The ecdysis activi ty observed in PSQG and PLPC may correlate with the detergent-like amphipha thic property of both compounds.,Although PLPC induced a similar ecdysis re sponse as PSQG, PLPC appeared to inhibit the growth of G. toxicus cultures, Preliminary results on the effects of PSQG on the dinoflagellates A Proroc entrum lima (Ehrenberg) Dodge and Coolia monotis Meunier did not parallel t he results observed in G. toxicus. This study demonstrated the existence of a factor from Bryopsis sp. that elicited a possible species-specific ecdys is response in G. toxicus cultures. This is the first report of a compound that induced ecdysis in G. toxicus or in any dinoflagellate.