Robertson's Mutator transposons in A-thaliana are regulated by the chromatin-remodeling gene Decrease in DNA Methylation (DDM1)

Robertson's Mutator transposable elements in maize undergo cycles of activi ty and then inactivity that correlate with changes in cytosine methylation. Mutator-like elements are present in the Arabidopsis genome but are heavil y methylated and inactive. These elements become demethylated and active in the chromatin-remodeling mutant ddm1 ((D) under bar ecrease in (D) under b ar NA (M) under bar ethylation), which leads to loss of heterochromatic DNA methylation. Thus, DNA transposons in plants appear to be regulated by chr omatin remodeling. In inbred ddm1 strains, transposed elements may account, in part, for mutant phenotypes unlinked to ddm1. Gene silencing and paramu tation are also regulated by DDM1, providing support for the proposition th at epigenetic silencing is related to transposon regulation.