Ultrastructural localisation by protein A-gold immunocytochemistry of 5-enolpyruvylshikimic acid 3-phosphate synthase in a plant cell culture which overproduces the enzyme.

Recently we have shown that cultured cells of the higher plant Corydalis sempervirens Pers., adapted to growth in the presence of high concentrations of the herbicide glyphosate, a potent specific inhibitor of the shikimate pathway enzyme 5-enolpyruvylshikimic acid 3-phosphate (EPSP) synthase (EC 2.5.1.19, 3-phosphoshikimate 1-carboxyvinyltransferase) oversynthesize the EPSP synthase protein (Smart et al., 1985, J. Biol. Chem. 260, 16338-16346). We now report that the EPSP synthase protein can be detected in cells of the adapted as well as of the non-adapted strain by the use of protein A-colloidal gold immunocytochemistry. The overproduced EPSP synthase in the glyphosate-adapted cells is located exclusively in the plastid and we find no evidence for the existence of extra-plastidic EPSP synthase in either strain.