Study : OsJMJ703, a Histone H3K4 Demethylase, Controls Transposon Activity in Rice
OsJMJ703, a Histone H3K4 Demethylase, Controls Transposon Activity in Rice
Retrotransposons are classified into long terminal repeat (LTR) or non-LTR retrotransoposons, and both types can mobilize in a “copy and paste” manner. Rice genome contains >40% of repetitive sequences or transposable elements (TEs) that scattered throughout the genome. TE activities are tightly regulated by distinct epigenetic mechanisms. Histone lysine methylation is catalyzed by SET domain group (SDG) protein and reversed by a family of Jumonji C (JmjC) domain-containing proteins. In rice, DNA methylation and histone methylation have been implicated in controlling copia-like LTR retrotransposon Tos17 activities. Whether any TEs are controlled by histone demethylase remains to be elusive. Here, we show that JMJ703 is a histone H3K4 specific demethylase in rice. Impaired JMJ703 disrupted genome-wide transcriptome and enhanced H3K4me3 resulting in pleiotropic defects. Two LINE elements, Karma and its N-terminal truncation were identified as direct targets of JMJ703 with increased frequency of transposition in jmj703, while Tos17 is unaffected. Our findings show that plants use H3K4me3 demethylase to constitutively remove active chromatin mark and maintain silencing status at a subset retrotransposons which localize in heterochromatin regions. Therefore, our work uncovers a novel mechanism to control retrotransposon activity by histone demethylation, which further strengthens the link between epigenetic silencing and genome stability. Overall design: Examination of differences in H3K4 between jmj703 and wild type.