EFFECT OF THE M-CENTER-DOT-ECORII METHYLTRANSFERASE-ENCODING GENE ON THE PHENOTYPE OF NICOTIANA-TABACUM TRANSGENIC CELLS

The EcoRII DNA methyltransferase (M . EcoRII; MTase) modifies a cytosi ne in the DNA sequence CCWGG which contains a CNG methylation motif ch aracteristic of plant DNA. The gene (ecoRllM) encoding this MTase has been cloned into the T-DNA of the wild-type Agrobacterium Ti-plasmid p TiC58 downstream from the plant expression nopaline synthase-encoding gene promoter. Nicotiana tabacum cells have been transformed with Agro bacterium tumefaciens harbouring this recombinant Ti-plasmid. The prim ary transformed tabacco tissue line has given rise to novel stable lin es which are morphologically distinctive. Southern hybridization analy sis of all transformed tissue lines has shown the presence, in each of them, of ecoRIIM. The tissue studied differed in morphology in callus culture, dependence on phytohormones and the ability to synthesize no paline.