Okadaic acid and PP2A cellular immunolocalization in Prorocentrum lima (Dinophyceae)

The toxicity of a Prorocentrum lima Ehrenberg strain from the French Medite rranean was compared with that of a Spanish strain of the same species. Alt hough the toxic profiles revealed by high-performance liquid chromatography were similar, showing okadaic acid (OA) and dinophysistoxin (DTX1), the Fr ench strain contained markedly less toxin. This difference was verified by immunofluorescence techniques for the intracellular localization of OA, whi ch showed sequestration of OA and its derivatives in vacuolar structures on the periphery of the cytoplasm, and these structures appeared to be less c oncentrated in the French strain at the same culture age. Okadaic acid and its target, protein-phosphatase PP2A, were detected simultaneously by label ing with specific antibodies. The immunolocalization of the protein in a sp herical structure close to the centrosomic region was confirmed for both st rains. Observations supported the hypothesis that the insensitivity of P. l ima strains to OA is due in part to sequestration of the inhibitory substan ce at a distance (area close to the nucleus) from the target substance, pho sphatase, thus preventing their contact.