Detection of DNA methylation pattern in thidiazuron-induced blueberry callus using methylation-sensitive amplification polymorphism

During the normal developmental process, programmed gene expression is an essential phenomenon in all organisms. In eukaryotes, DNA methylation plays an important role in the regulation of gene expression. The extent of cytosine methylation polymorphism was evaluated in leaf tissues collected from the greenhouse grown plants and in in vitro-derived callus of three lowbush and one hybrid blueberry genotypes, using methylation-sensitive amplification polymorphism (MSAP) technique. Callus formation started from the leaf segments after 4 weeks of culture on a thidiazuron (TDZ) containing medium. Maximum callus formation (98 %) was observed in the hybrid blueberry at 1.0 mg dm(-3) TDZ. Although noticeable changes in cytosine methylation pattern were detected within the MSAP profiles of both leaf and callus tissues, methylation events were more polymorphic in calli than in leaf tissues. The number of methylated CCGG sites varied significantly within the genotypes ranging from 75 to 100 in leaf tissues and from 215 to 258 in callus tissues. Differences in the methylation pattern were observed not only in a tissue-specific manner but also within the genotype in a treatment specific manner. These results demonstrated the unique effect of TDZ and the tissue culture process on DNA methylation during callus development.