[Analysis of mosaic expression of the nptII gene in transgenic tobacco plant lines contrasting in mosaicism].

Differences in the frequency of occurrence of plants with the mosaic phenotype between the Nu5 and Nu6 lines of transgenic tobacco (Nicotiana tabacum) plants remained irrespective of the allelic state of the nptII marker gene. Transition of the nptII gene from the hemizygous state (T3) to the homozygous state (T4) was accompanied by an increase in the frequency of mosaics in both lines. Transition from the homozygous state (T4) into the hemizygous state (F1) resulted in a further increase in the frequency of mosaic plants in the Nu5 line, whereas in the Nu6 line this parameter remained at a high level. Hypermethylation of the pMAS promoter in plants of both lines, as well as differences in the degree of methylation of cytosines in the 5'-region of the coding part of a truncated nptII gene copy between the Nu5 and Nu6 lines, pointed to epigenetic regulation of the mosaic expression of the nptII gene.