Meiotically and mitotically stable inheritance of DNA hypomethylation induced by ddm1 mutation of Arabidopsis thaliana

In contrast to mammalian epigenetic phenomena, where resetting of gene expr ession generally occurs in each generation, epigenetic states of plant gene s are often stably transmitted through generations. The Arabidopsis mutatio n ddm1 causes a 70% reduction in genomic 5-methylcytosine level. We have pr eviously shown that the ddm1 mutation results in an accumulation of a varie ty of developmental abnormalities by slowly inducing heritable changes in o ther loci. Each of the examined ddm1-induced developmental abnormalities is stably transmitted even when segregated from the potentiating ddm1 mutatio n. Here, the inheritance of DNA hypomethylation induced by ddm1 was examine d in outcross progeny by HPLC and Southern analyses. The results indicate t hat (i) DDM1 gene function is not necessary during the gametophyte stage, ( ii) ddm1 mutation is completely recessive, and (iii) remethylation of seque nces hypomethylated by the ddm1 mutation is extremely slow or nonexistent e ven in wild-type DDM1 backgrounds. The stable transmission of DNA methylati on status maybe related to the meiotic heritability of the ddm1-induced dev elopmental abnormalities.