抄録
Phosphinothricin (PPT) is the active ingredient in bialaphos, which specifically inhibits glutamine synthetase in land plants. We isolated a novel PPT-resistant gene from a soil bacterium, Nocardia sp., and characterized it. The encoded protein, consisting of 177 amino acids, showed significant similarity to bacterial N-acetyltransferases, and we originally designated the gene MAT (methionine sulfone N-acetyltransferase). The recombinant MAT protein exhibited functions as a methionine sulfone and PPT N-acetyltransferase in vitro. The PPT N-acetyltransferase activity reached the maximum at pH 8–8.5, indicating that the protein might optimally function in chloroplasts. We therefore constructed a MAT gene, encoding the enzyme with a chloroplast-localizing signal in its amino-terminus. Plant transformation with the construct resulted in the generation of PPT-resistant rice and Arabidopsis. Furthermore, the transformed Arabidopsis was selectable in a synthetic medium containing PPT. The MAT gene thus facilitated establishment of herbicide-resistant plants, and as a new selectable gene marker.
