title: required to maintain repression2 is a novel protein that facilitates locus-specific paramutation in maize.
abstract: Meiotically heritable epigenetic changes in gene regulation known as paramutations are facilitated by poorly understood trans-homolog interactions. Mutations affecting paramutations in maize (Zea mays) identify components required for the accumulation of 24-nucleotide RNAs. Some of these components have Arabidopsis thaliana orthologs that are part of an RNA-directed DNA methylation (RdDM) pathway. It remains unclear if small RNAs actually mediate paramutations and whether the maize-specific molecules identified to date define a mechanism distinct from RdDM. Here, we identify a novel protein required for paramutation at the maize purple plant1 locus. This required to maintain repression2 (RMR2) protein represents the founding member of a plant-specific clade of predicted proteins. We show that RMR2 is required for transcriptional repression at the Pl1-Rhoades haplotype, for accumulation of 24-nucleotide RNA species, and for maintenance of a 5-methylcytosine pattern distinct from that maintained by RNA polymerase IV. Genetic tests indicate that RMR2 is not required for paramutation occurring at the red1 locus. These results distinguish the paramutation-type mechanisms operating at specific haplotypes. The RMR2 clade of proteins provides a new entry point for understanding the diversity of epigenomic control operating in higher plants.
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3200, USA.
authors.forename: Joy-El R
authors.initials: JE
authors.lastname: Barbour
authors.forename: Irene T
authors.initials: IT
authors.lastname: Liao
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Stonaker
authors.forename: Jana P
authors.initials: JP
authors.lastname: Lim
authors.forename: Clarissa C
authors.initials: CC
authors.lastname: Lee
authors.forename: Susan E
authors.initials: SE
authors.lastname: Parkinson
authors.forename: Jerry
authors.initials: J
authors.lastname: Kermicle
authors.forename: Stacey A
authors.initials: SA
authors.lastname: Simon
authors.forename: Blake C
authors.initials: BC
authors.lastname: Meyers
authors.forename: Rosalind
authors.initials: R
authors.lastname: Williams-Carrier
authors.forename: Alice
authors.initials: A
authors.lastname: Barkan
authors.forename: Jay B
authors.initials: JB
authors.lastname: Hollick
mesh_terms: D044503:5-Methylcytosine / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D019175:DNA Methylation / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D006239:Haplotypes; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics*; D003313:Zea mays / Q000235:genetics* / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D044503:5-Methylcytosine