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Abstract In mammals and plants, cytosine DNA methylation is essential for the epigenetic repression of transposable elements and foreign DNA. In plants, DNA methylation is guided by small interfering RNAs (siRNAs) in a self-reinforcing cycle termed RNA-directed DNA methylation (RdDM). RdDM requires the specialized RNA polymerase V (Pol V), and the key unanswered question is how Pol V is first recruited to new target sites without pre-existing DNA methylation. We find that Pol V follows and is dependent on the recruitment of an AGO4-clade ARGONAUTE protein, and any siRNA can guide the ARGONAUTE protein to the new target locus independent of pre-existing DNA methylation. These findings reject long-standing models of RdDM initiation and instead demonstrate that siRNA-guided ARGONAUTE targeting is necessary, sufficient and first to target Pol V recruitment and trigger the cycle of RdDM at a transcribed target locus, thereby establishing epigenetic silencing.
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A null allele of the pol IV second subunit impacts stature and reproductive development in Oryza sativa
SUMMARY All eukaryotes possess three DNA‐dependent RNA polymerases, Pols I–III, while land plants possess two additional polymerases, Pol IV and Pol V. Derived through duplication of Pol II subunits, Pol IV produces 24‐nt short interfering RNAs that interact with Pol V transcripts to targetde novoDNA methylation and silence transcription of transposons. Members of the grass family encode additional duplicated subunits of Pol IV and V, raising questions regarding the function of each paralog. In this study, we identify a null allele of the putative Pol IV second subunit,NRPD2, and demonstrate that NRPD2 is the sole subunit functioning with NRPD1 in small RNA production and CHH methylation in leaves. Homozygousnrpd2mutants have neither gametophytic defects nor embryo lethality, although adult plants are dwarf and sterile.
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- Award ID(s):
- 1929678
- PAR ID:
- 10374785
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- The Plant Journal
- Volume:
- 111
- Issue:
- 3
- ISSN:
- 0960-7412
- Page Range / eLocation ID:
- p. 748-755
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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