Abstract
Arabidopsis mutants in DNA methyltransferase provide suitable systems to examine the transposon control by DNA methylation, since they are viable.
MET1 (METHYLTRANSFERASE 1) is necessary for maintaining methylation at CpG site. Arabidopsis additionally methylates at non-CpG site using CMT3 (CHROMOMETHYLASE 3). The third gene necessary for DNA methylation is DDM1. The mutation in DDM1 (DECREASE IN DNA METHYLATION 1) gene reduced both CpG and non-CpG methylation and induced several developmental abnormalities. Through genetic analysis of one of them, we have identified mobile genetic elements CACTA in Arabidopsis.
CACTA transposon transposed at high frequency specifically in ddm1-induced hypomethylation background. DDM1 gene encodes not DNA methyltransferase but chromatin remodeling factor, suggesting immobilization of these elements through chromatin remodeling.
To directly test if the loss of DNA methylation is sufficient for mobilization of transposons, we examined CACTA behavior in two mutants in DNA methyltransferase gene, MET1 and CMT3.
