Heritable alteration in DNA methylation pattern occurred specifically at mobile elements in rice plants following hydrostatic pressurization

Intrinsic DNA methylation pattern is an integral component of the epigenetic network in many eukaryotes. Exploring the extent to which DNA methylation patterns can be altered under a specific condition is important for elucidating the biological functions of this epigenetic modification. This is of added significance in plants wherein the newly acquired methylation patterns can be inherited through organismal generations. We report here that DNA methylation patterns of mobile elements but not of cellular genes were specifically altered in rice plants following hydrostatic pressurization. This was evidenced by methylation-sensitive gel-blot analysis, which showed that 10 out of 10 studied low-copy transposons and retrotransposons manifested methylation alteration in at least one of the 8 randomly chosen pressure-treated plants, whereas none of the 16 studied low-copy cellular genes showed any change. Both gel-blotting and genome-wide fingerprinting indicated that the methylation alteration in mobile elements was not accompanied by a general genetic instability. Progeny analysis indicated retention of the altered methylation patterns in most progeny plants, underscoring early occurrence of the alterations, and their faithful epigenetic inheritance.