MICROCYSTIN UPTAKE INHIBITS GROWTH AND PROTEIN PHOSPHATASE-ACTIVITY IN MUSTARD (SINAPIS-ALBA L.) SEEDLINGS

Mustard (Sinapis alba L.) seeds were cultivated for seven days on a so lid nutrient medium supplemented with 0 40 mu g microcystin-RR per ml. Microcystin-RR affected seedling growth (IC50 0.8 mu g/ml) and microc ystin concentrations greater than or equal to 5.0 mu g/ml produced mal formed plants. The inhibition of protein phosphatase 1 and 2A activity correlated with the growth inhibition. The seedlings were also shown to take up H-3-dihydromicrocystin-LR derived radioactivity up to a lev el corresponding to ca. 80 ng toxin per mg plant protein. (C) 1998 Els evier Science Ltd. All rights reserved.