title: AGO4 is specifically required for heterochromatic siRNA accumulation at Pol V-dependent loci in Arabidopsis thaliana.
abstract: In plants, 24 nucleotide long heterochromatic siRNAs (het-siRNAs) transcriptionally regulate gene expression by RNA-directed DNA methylation (RdDM). The biogenesis of most het-siRNAs depends on the plant-specific RNA polymerase IV (Pol IV), and ARGONAUTE4 (AGO4) is a major het-siRNA effector protein. Through genome-wide analysis of sRNA-seq data sets, we found that AGO4 is required for the accumulation of a small subset of het-siRNAs. The accumulation of AGO4-dependent het-siRNAs also requires several factors known to participate in the effector portion of the RdDM pathway, including RNA POLYMERASE V (POL V), DOMAINS REARRANGED METHYLTRANSFERASE 2 (DRM2) and SAWADEE HOMEODOMAIN HOMOLOGUE 1 (SHH1). Like many AGO proteins, AGO4 is an endonuclease that can 'slice' RNAs. We found that a slicing-defective AGO4 was unable to fully recover AGO4-dependent het-siRNA accumulation from ago4 mutant plants. Collectively, our data suggest that AGO4-dependent siRNAs are secondary siRNAs dependent on the prior activity of the RdDM pathway at certain loci.
authors.affiliation: Intercollege Plant Biology Ph.D. Program, Huck Institutes of the Life Sciences, Penn State University, University Park, PA, 16802, USA.|Department of Biology, Penn State University, University Park, PA, 16802, USA.
authors.forename: Feng
authors.initials: F
authors.lastname: Wang
authors.affiliation: Intercollege Plant Biology Ph.D. Program, Huck Institutes of the Life Sciences, Penn State University, University Park, PA, 16802, USA.|Department of Biology, Penn State University, University Park, PA, 16802, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Axtell
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000382:microbiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D060565:Argonaute Proteins / Q000235:genetics / Q000378:metabolism*; D012321:DNA-Directed RNA Polymerases / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000502:physiology; D020868:Gene Silencing / Q000502:physiology; D006570:Heterochromatin / Q000235:genetics; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics / Q000502:physiology
chemical_list: C471209:AGO4 protein, Arabidopsis; D029681:Arabidopsis Proteins; D060565:Argonaute Proteins; D006570:Heterochromatin; D018398:Homeodomain Proteins; D018749:RNA, Plant; D034741:RNA, Small Interfering; C568760:SHH1 protein, Arabidopsis; D008780:Methyltransferases; C470732:DRM2 protein, Arabidopsis; C499181:RNA polymerase IV, Arabidopsis; C538841:RNA polymerase V, Arabidopsis; D012321:DNA-Directed RNA Polymerases
keywords: ARGONAUTE4; heterochromatic siRNA accumulation; sRNA-seq; secondary heterochromatic siRNAs; slicing ability