The EcoRII DNA methyltransferase (M.EcoRII; MTase) modifies a cytosine in the DNA sequence CCWGG which contains a CNG methylation motif characteristic of plant DNA. The gene (ecoRIIM) encoding this MTase has been cloned into the T-DNA of the wild-type Agrobacterium Ti-plasmid pTiC58 downstream from the plant expression nopaline synthase-encoding gene promoter. Nicotiana tabacum cells have been transformed with Agrobacterium tumefaciens harbouring this recombinant Ti-plasmid. The primary transformed tabacco tissue line has given rise to novel stable lines which are morphologically distinctive. Southern hybridization analysis 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 nopaline. © 1995.