J. Biol. Chem., Vol. 260, Issue 30, 16338-16346, Dec, 1985
Selective overproduction of 5-enol-pyruvylshikimic acid 3-phosphate synthase in a plant cell culture which tolerates high doses of the herbicide glyphosate
CC Smart, D Johanning, G Muller and N Amrhein
Cultured cells of the higher plant Corydalis sempervirens Pers. which had
been adapted to growing in the presence of 5 mM glyphosate (N-
[phosphonomethyl]-glycine), a herbicide and a potent specific inhibitor of
the shikimate pathway enzyme 5-enol-pyruvylshikimate-3-phosphate (EPSP)
synthase, had a nearly 40-fold increased level of the extractable activity
of EPSP synthase. Activities of five other shikimate pathway enzymes were,
however, similar in the adapted and nonadapted cells, and the
concentrations of the free aromatic amino acids in the two cell lines were
also similar. EPSP synthases purified from glyphosate-adapted, as well as
nonadapted cells, had identical physical, kinetic, and immunological
properties, which indicated that the glyphosate-sensitive enzyme was
overproduced in the adapted culture. Overproduction of EPSP synthase in the
adapted culture was unequivocally established by two-dimensional
polyacrylamide gel electrophoresis, as well as by one-dimensional sodium
dodecyl sulfate- gradient gel electrophoresis and quantitation of EPSP
protein by immunoassay after transfer to nitrocellulose membranes. While
about 0.06% of the total soluble protein from nonadapted cells was EPSP
synthase protein, the proportion was 2.6% in the adapted cells. In vivo
pulse-labeling experiments with [35S]methionine established that the
adapted cells have an increased rate of EPSP synthase protein synthesis.