Mutants of Arabidopsis gene responsible for DNA methylation show different growth inhibition in the presence of DNA methylation inhibitors. DNA methylation plays an important role in regulating the transposon activation in plants. Therefore, there has been used chemical restriction of DNA methyltransferases as a temporary alternative in order to study the effect of DNA methylation loss in Arabidopsis thaliana. To understand the effect of DNA methylation, mutants of Arabidopsis thaliana seedlings were treated with either 5-aza-2'-deoxycytidine (5-Aza-2') or Zebularine (Zeb), which is known to be an effective chemical demethylation agent.

In this study, we use phenotype results of DNA methylation of the effects of either Zebularine or 5-Aza-2'-deoxycytidine treatment on mutants of Arabidopsis thaliana seedlings. DNA methylation raise was observed in Aza-treated plants than control plants. In this result, there have been revealed that, DNA methylation inhibitors – 5-Aza-2'-deoxycytidine treatment inhibiting DNA methyltransferase activity enhanced on cmt3-Ex, cmt3-Int, cmt3-St, cmt2/3 mutants of Arabidopsis.

Based on the results of the research, it was found that, growth inhibition of mutants of A. thaliana occurs under 5-Aza-2'-deoxycytidine treatment. As a result of the research there have been investigated that, the cmt3 mutants [cmt3-Ex, cmt3-Int, cmt3-St, cmt2/3] showed less growth inhibition than the wild type under 5-Aza-2'-deoxycytidine treatment.

Mutants of Arabidopsis thaliana seedlings which treated with Zebularine, showed a slight general growth inhibition on comparison with the mutants of A. thaliana seedlings on MS. In contrast to the cmt3 mutants on 5-Aza-2' treatment, there have not been observed any DNA methylation on cmt3 mutants treated with Zebularine.

The result showed that, three mutants: cmt3-Ex, cmt3-Int, cmt3-St, cmt2/3 of Arabidopsis gene responsible for DNA methylation have been stronger on the comparison with the Col WT in 5-aza-2'-deoxycytidine (5-Aza-2') treatment. When analyzing phenotype results, it has been cleared that, all the MS plate seedlings have been showed well development than 5-Aza-2' treatment.