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

The toxicity of a Prorocentrum lima Ehrenberg strain from the French Mediterranean was compared with that of a Spanish strain of the same species. Although the toxic profiles revealed by high-performance liquid chromatography were similar, showing okadaic acid (OA) and dinophysistoxin (DTX1), the French strain contained markedly less toxin. This difference was verified by immunofluorescence techniques for the intracellular localization of OA, which showed sequestration of OA and its derivatives in vacuolar structures on the periphery of the cytoplasm, and these structures appeared to be less concentrated in the French strain at the same culture age. Okadaic acid and its target, protein-phosphatase PP2A, were detected simultaneously by labeling with specific antibodies. The immunolocalization of the protein in a spherical structure close to the centrosomic region was confirmed for both strains. Observations supported the hypothesis that the insensitivity of P. lima strains to OA is due in part to sequestration of the inhibitory substance at a distance (area close to the nucleus) from the target substance, phosphatase, thus preventing their contact.