Identification of DMN in the BBL-suppressed tobacco roots. A, Gas-liquid chromatograms of alkaloid fractions from the cell extracts of the wild type (WT) and the KR2 line, along with the DMN standard. DMN (retention time, 19.7 min) accumulated in the KR2 roots but not in wild-type roots. B, Mass fragment patterns of the DMN peak in the KR2 roots and of the authentic DMN. C, Chemical structures of DMN and nicotine.