title: The Polycomb group protein CLF emerges as a specific tri-methylase of H3K27 regulating gene expression and development in Physcomitrella patens.
abstract: Packaging of eukaryotic DNA largely depends on histone modifications that affect the accessibility of DNA to transcriptional regulators, thus controlling gene expression. The Polycomb group (PcG) chromatin remodeling complex deposits a methyl group on lysine 27 of histone 3 leading to repressed gene expression. Plants encode homologs of the Enhancer of zeste (E(z)), a component of the PcG complex from Drosophila, one of which is a SET domain protein designated CURLY LEAF (CLF). Although this SET domain protein exhibits a strong correlation with the presence of the H3K27me3 mark in plants, the methyl-transferase activity and specificity of its SET domain have not been directly tested in-vivo. Using the evolutionary early-diverged land plant model species Physcomitrella patens we show that abolishment of a single copy gene PpCLF, as well as an additional member of the PcG complex, FERTILIZATION-INDEPENDENT ENDOSPERM (PpFIE), results in a specific loss of tri-methylation of H3K27. Using site-directed mutagenesis of key residues, we revealed that H3K27 tri-methylation is mediated by the SET domain of the CLF protein. Moreover, the abolishment of H3K27me3 led to enhanced expression of transcription factor genes. This in turn led to the development of fertilization-independent sporophyte-like structures, as observed in PpCLF and PpFIE null mutants. Overall, our results demonstrate the role of PpCLF as a SET protein in tri-methylation of H3K27 in-vivo and the importance of this modification in regulating the expression of transcription factor genes involved in developmental programs of P. patens.
authors.affiliation: Department of Molecular Biology and Ecology of Plants, Tel-Aviv University, Tel-Aviv 69978, Israel.
authors.forename: Idan
authors.initials: I
authors.lastname: Pereman
authors.affiliation: Department of Molecular Biology and Ecology of Plants, Tel-Aviv University, Tel-Aviv 69978, Israel; Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, Faculty of Agriculture, Hebrew University of Jerusalem, Rehovot 7610001, Israel.
authors.forename: Assaf
authors.initials: A
authors.lastname: Mosquna
authors.affiliation: Department of Molecular Biology and Ecology of Plants, Tel-Aviv University, Tel-Aviv 69978, Israel.
authors.forename: Aviva
authors.initials: A
authors.lastname: Katz
authors.affiliation: Plant Biotechnology, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany.
authors.forename: Gertrud
authors.initials: G
authors.lastname: Wiedemann
authors.affiliation: Plant Biotechnology, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Lang
authors.affiliation: Plant Biotechnology, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany.
authors.forename: Eva L
authors.initials: EL
authors.lastname: Decker
authors.affiliation: National Institute for Basic Biology, Okazaki 444-8585, Japan; Department of Basic Biology, The Graduate University for Advanced Studies, Okazaki 444-8585, Japan.
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Tamada
authors.affiliation: National Institute for Basic Biology, Okazaki 444-8585, Japan.
authors.forename: Takaaki
authors.initials: T
authors.lastname: Ishikawa
authors.affiliation: Advanced Science Research Center, Kanazawa University, Kanazawa 920-0934, Japan; ERATO, Okazaki 444-8585, Japan.
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Nishiyama
authors.affiliation: National Institute for Basic Biology, Okazaki 444-8585, Japan; Department of Basic Biology, The Graduate University for Advanced Studies, Okazaki 444-8585, Japan; ERATO, Okazaki 444-8585, Japan.
authors.forename: Mitsuyasu
authors.initials: M
authors.lastname: Hasebe
authors.affiliation: Plant Biotechnology, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany; FRIAS - Freiburg Institute for Advanced Studies, 79104 Freiburg, Germany; BIOSS - Centre for Biological Signaling Studies, 79104 Freiburg, Germany. Electronic address: ralf.reski@biologie.uni-freiburg.de.
authors.forename: Ralf
authors.initials: R
authors.lastname: Reski
authors.affiliation: Department of Molecular Biology and Ecology of Plants, Tel-Aviv University, Tel-Aviv 69978, Israel; FRIAS - Freiburg Institute for Advanced Studies, 79104 Freiburg, Germany; The Manna Center Program for Food Safety & Security, Tel Aviv University, 69978, Israel. Electronic address: niro@tauex.tau.ac.il.
authors.forename: Nir
authors.initials: N
authors.lastname: Ohad
mesh_terms: D000595:Amino Acid Sequence; D019068:Bryopsida / Q000235:genetics* / Q000254:growth & development*; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D000076983:Histone Methyltransferases; D011495:Histone-Lysine N-Methyltransferase / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D006657:Histones / Q000737:chemistry / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000502:physiology; D008239:Lysine / Q000378:metabolism; D008745:Methylation; D008969:Molecular Sequence Data; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D063146:Polycomb-Group Proteins / Q000502:physiology*; D017386:Sequence Homology, Amino Acid
chemical_list: D006657:Histones; D018398:Homeodomain Proteins; D063146:Polycomb-Group Proteins; D000076983:Histone Methyltransferases; D011495:Histone-Lysine N-Methyltransferase; D008239:Lysine
keywords: Curly leaf; Epigenetic regulation; H3K27 methylation; Histone code; Physcomitrella patens; SET domain