title: Chromatin assembly factor CAF-1 represses priming of plant defence response genes.
abstract: Plants have evolved efficient defence systems against pathogens that often rely on specific transcriptional responses. Priming is part of the defence syndrome, by establishing a hypersensitive state of defence genes such as after a first encounter with a pathogen. Because activation of defence responses has a fitness cost, priming must be tightly controlled to prevent spurious activation of defence. However, mechanisms that repress defence gene priming are poorly understood. Here, we show that the histone chaperone CAF-1 is required to establish a repressed chromatin state at defence genes. Absence of CAF-1 results in spurious activation of a salicylic acid-dependent pathogen defence response in plants grown under non-sterile conditions. Chromatin at defence response genes in CAF-1 mutants under non-inductive (sterile) conditions is marked by low nucleosome occupancy and high H3K4me3 at transcription start sites, resembling chromatin in primed wild-type plants. We conclude that CAF-1-mediated chromatin assembly prevents the establishment of a primed state that may under standard non-sterile growth conditions result in spurious activation of SA-dependent defence responses and consequential reduction of plant vigour.
authors.affiliation: Department of Plant Biology, Uppsala BioCenter, Swedish University of Agricultural Sciences and Linnean Center for Plant Biology, Uppsala SE-75007, Sweden.
authors.forename: Iva
authors.initials: I
authors.lastname: Mozgová
authors.affiliation: Department of Biology and Zurich-Basel Plant Science Center, ETH Zurich, Zurich CH-8092, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Wildhaber
authors.affiliation: Department of Plant Biology, Uppsala BioCenter, Swedish University of Agricultural Sciences and Linnean Center for Plant Biology, Uppsala SE-75007, Sweden.
authors.forename: Qinsong
authors.initials: Q
authors.lastname: Liu
authors.affiliation: Department of Biology, University of Fribourg, Ch. du Musée 10, Fribourg 1700, Switzerland.
authors.forename: Eliane
authors.initials: E
authors.lastname: Abou-Mansour
authors.affiliation: Department of Biology, University of Fribourg, Ch. du Musée 10, Fribourg 1700, Switzerland.
authors.forename: Floriane
authors.initials: F
authors.lastname: L'Haridon
authors.affiliation: Department of Biology, University of Fribourg, Ch. du Musée 10, Fribourg 1700, Switzerland.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Métraux
authors.affiliation: Department of Biology and Zurich-Basel Plant Science Center, ETH Zurich, Zurich CH-8092, Switzerland.
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Gruissem
authors.affiliation: Department of Plant Biology, Uppsala BioCenter, Swedish University of Agricultural Sciences and Linnean Center for Plant Biology, Uppsala SE-75007, Sweden.
authors.forename: Daniel
authors.initials: D
authors.lastname: Hofius
authors.affiliation: Department of Plant Biology, Uppsala BioCenter, Swedish University of Agricultural Sciences and Linnean Center for Plant Biology, Uppsala SE-75007, Sweden.
authors.forename: Lars
authors.identifier: http://orcid.org/0000-0002-6645-1862
authors.initials: L
authors.lastname: Hennig