ARGONAUTE1-binding Tudor domain proteins function in small interfering RNA production for RNA-directed DNA methylation

Takahito Takei, Michio Tsukada, Kentaro Tamura, Ikuko Hara-Nishimura, Yoichiro Fukao, Yukio Kurihara, Minami Matsui, Hidetoshi Saze, Masayuki Tsuzuki, Yuichiro Watanabe, Takahiro Hamada

Transposable elements (TEs) contribute to plant evolution, development, and adaptation to environmental changes, but the regulatory mechanisms are largely unknown. RNA-directed DNA methylation (RdDM) is one TE regulatory mechanism in plants. Here, we identified that novel ARGONAUTE 1 (AGO1)-binding Tudor domain proteins Precocious dissociation of sisters C/E (PDS5C/E) are involved in 24-nt siRNA production to establish RdDM on TEs in Arabidopsis thaliana PDS5 family proteins are subunits of the eukaryote-conserved cohesin complex. However, the double mutant lacking angiosperm-specific subfamily PDS5C and PDS5E (pds5c/e) exhibited different developmental phenotypes and transcriptome compared with those of the double mutant lacking eukaryote-conserved subfamily PDS5A and PDS5B (pds5a/b), suggesting that the angiosperm-specific PDS5C/E subfamily has a unique function in angiosperm plants. Proteome and imaging analyses revealed that PDS5C/E interact with AGO1. The pds5c/e double mutant had defects in 24-nt siRNA accumulation and CHH DNA methylation on TEs. In addition, some lncRNAs that accumulated in the pds5c/e mutant were targeted by AGO1-loading 21-nt miRNAs and 21-nt siRNAs. These results indicate that PDS5C/E and AGO1 participate in 24-nt siRNA production for RdDM in the cytoplasm. These findings indicate that angiosperm plants evolved a new regulator, the PDS5C/E subfamily, to control the increase in TEs during angiosperm evolution.