A SINGLE TREATMENT OF RICE SEEDLINGS WITH 5-AZACYTIDINE INDUCES HERITABLE DWARFISM AND UNDERMETHYLATION OF GENOMIC DNA

A single exposure of germinated rice seeds (Oryza sativa) to either of the DNA demethylating agents 5-azacytidine (azaC) or 5-azadeoxycytidine (azadC) induced dwarf plants. At maturity, seeds treated with azaC exhibited normal morphological characteristics in comparison with untreated controls except that their height (total stem length) was reduced by about 15%. The M1 progeny, obtained by self-fertilization of an azaC-induced dwarf plant, segregated into dwarf (35%) and apparently tall types (65%). The M2 progenies, obtained by self-fertilization of dwarf M1 plants, were also dwarf, while those from tall M1 plants were only tall. Genomic DNA isolated from mature leaves of azaC-treated seeds showed about a 16% reduction in the 5-methylcytosine (m5C) content in comparison with DNA from untreated samples. A similar reduction in the m5C content was also observed in the M1 and M2 progenies. Thus, both undermethylation and dwarfism induced by azaC treatment were heritable. The results suggest that azaC induced demethylation of genomic DNA, which caused an altered pattern of gene expression and consequently a reduction in plant stem length. © 1990 Springer-Verlag.