Antibiotic-induced DNA methylation changes in calluses of Arabidopsis thaliana

This study was carried out to determine the involvement of the antibiotic kanamycin, commonly used as a selective agent in transformation protocols, in the phenomenon of somaclonal variation. Both genetic and epigenetic events were looked for. Two complementary approaches were used to evaluate global methylation changes in the genome of callus derived from the leaves of Arabidopsis thaliana L.; immunolabelling using monoclonal-antibodies raised against 5-methylcytosine in order to define the relative abundance of methylated cytosine; the analysis of methylation-sensitive polymorphism technique (MSAP) to assess methylation changes at CCGG sequences. In addition, the same samples were analysed using AFLPs in order to determine the extent of genomic change with respect to callus grown in the absence of kanamycin and plants grown from seed. The use of kanamycin as a selective agent caused extensive methylation changes in the genome with both hyper- and hypomethylation events seen. However, the net result was genome-wide hypomethylation: this effect was dosage dependent; the higher the dose, the greater the effect. At the same time, sequence mutation was detected.