Genetic diversity in French Polynesian strains of the ciguatoxic dinoflagellate Gambierdiscus toxicus : RFLP and sequence analysis on the SSU and LSU rRNA genes.

Publication Type  Book Chapter
Year of Publication  1998
Authors  Chinain, M.; Germain, M.; Sako, Y.; Pauillac, S.; Legrand, A-M.
Book Title  Harmful Algae
City  Xunta de Galicia (Spain)
Publisher  Reguera B, Blanco J, Fernandez ML, Wyatt T (Eds). Intergovernmental Oceanographic Commission of UNESCO
Pages  287-90
Language  eng

The genetic diversity among 19 strains of the ciguatera-causing dinoflagellate Gambierdiscus toxicus Adachi & Fukuyo collected from French Polynesia was investigated by RFLP and sequence analyses of their SSU and LSU rDNA, respectively. Preliminary results indicated that G. toxicus is comprised of numerous genetically distinct strains. Digestion of the SSU rRNA gene with the enzyme RsaI yielded 6 distinct restriction types. In some cases strains isolated concurrently from the same site - e.g. Teahupoo, Tubuai or Mangareva - exhibited distinct restriction profiles, suggesting a multiclonal origin for naturally occuring blooms, which may account in part for differences in severity of ciguatera incidents. Sequence comparison of a fragment of the LSU rDNA for 15 strains also revealed genetic variations in G. toxicus. Strains tended to form 2 different clusters representative of northern and southern localities in French Polynesia. However, grouping of the 15 strains examined did not reflect ciguatoxin production characteristics. The existence of a significant genetic variation within isolates of G. toxicus, yet sharing a common general morphology, stresses the need for the characterization of new molecular markers useful for fine-scale population and (or) taxonomic analyses of the genus Gambierdiscus.

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