THE MODE OF ACTION OF GLUFOSINATE IN ALGAE - THE ROLE OF UPTAKE AND NITROGEN ASSIMILATION PATHWAYS

The purpose of this work was to investigate the in-vivo mode of action of glufosinate in comparison with that of the known glutamine synthet ase inhibitor, methionine sulfoximine, in photoautotrophic microorgani sms. Using the eukaryotic green alga Chlorella fusca (Shih. & Krauss) and the cyanobacterium Anacystis nidulans (Kratz & Myers), currently d eveloped [N-15]NMR pulse-labelling techniques have been employed to st udy the inhibition of ammonia assimilation. The results show that, whi le methionine sulfoximine immediately blocks glutamine synthesis, gluf osinate action requires an induction process in both organisms investi gated, possibly indicating the de-novo synthesis of an amino acid memb rane carrier. In addition, the observed ability of C. fusca to incorpo rate nitrogen into glutamate under glutamine synthetase-inhibiting con ditions is explicable by an anabolic function of a glutamate dehydroge nase in this organism. This might explain the large differences in obs erved species sensitivity to glufosinate exposure.