Abstract
DDM1 (Decreased in DNA Methylation) encodes a chromatin-remodeling factor is thought to be necessary for maintenance of cytosine methylation in genomic DNA. The ddm1 mutants in Arabidopsis confer hypomethylation in repetitive sequences and induce epi-alleles stochastically. While Arabidopsis bears the single DDM1 gene, two redundant DDM1 genes, OsDDM1a and OsDDM1b, were annotated in rice. We have developed an efficient and generally applicable gene targeting (GT) procedure in rice, which is based on a strong positive-negative selection in a large-scale Agrobacterium-mediated transformation, followed by PCR screening. To elucidate the function of rice DDM1 genes, we are attempting to isolate transgenic rice plants having these OsDDM1 genes modified by GT. We have obtained several independent transgenic lines with either OsDDM1a or OsDDM1b modified in the heterozygous condition and their segregants with one of the mutated alleles in the homozygous condition. We will present our results of these mutants.
