GSE106971
The Anaphase Promoting Complex/Cyclosome degrades DMS3 to maintain RNA-directed DNA Methylation in Arabidopsis [small RNA-seq]
RNA-directed DNA methylation (RdDM) plays an essential role in transposable element (TE) silencing in plants. In the Arabidopsis RdDM pathway, the DDR complex containing DRD1, DMS3, and RDM1, is necessary for recruiting Pol V to transcribe scaffold RNA. Although the role of DDR is known, the mechanism by which the DDR complex is regulated remains unexplored. Here, we demonstrate that the Anaphase Promoting Complex/Cyclosome (APC/C) monitors the assembly of the DDR complex by targeting DMS3 for degradation. We show that a subset of Pol V-dependent RdDM loci are de-repressed in apc/c mutants, accompanied by defective recruitment and transcription of Pol V. APC/C targets DMS3 for ubiquitination and degradation in a D box-dependent manner, and the D-box-mutated DMS3 fails to complement the dms3 mutant. Competitive binding assays shows that the dosage of DMS3 is critical for the assembly of the DDR complex, and in vivo gel filtration analysis shows that the assembly of both DDR and Pol V is compromised in the apc8 mutant. These findings uncover a safeguard role of APC/C-mediated DMS3 degradation in the assembly of the DDR complex, and provide a direct link between selective protein degradation and RdDM. Overall design: Illumina sequencing of duplicate small RNA libraries from inflorescences