title: Cold stress selectively unsilences tandem repeats in heterochromatin associated with accumulation of H3K9ac.
abstract: Knobs are cytologically observable major interstitial heterochromatin present on maize nuclei, which consist of highly tandem-repetitive elements that are always silenced. Here we investigated the genome-wide change of H3K9ac, an active chromatin mark, during cold stress using chromatin immunoprecipitation sequencing (ChIP-Seq) and identified differential cold-induced H3K9ac enrichment at repetitive sequences in maize. More detailed analysis of two knob-associated tandem-repetitive sequences, 180-bp and TR-1, demonstrated that cold activated their transcription and this cold-induced transcriptional activation of repetitive sequences is selective, transient, and associated with an increase in H3K9ac and a reduction in DNA methylation and H3K9me2. Furthermore, knob sequence expression is accompanied by localized chromatin remodelling and silencing is recovered upon prolonged treatment. In addition, no evidence of copy number change and rearrangement of these repetitive elements are found in plants subjected to cold stress. These results suggest that cold-mediated unsilencing of heterochromatic tandem-repeated sequences, accompanied with epigenetic regulation, might play an important role in the adaptation of plants to cold stimuli.
authors.affiliation: State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan 430072, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Hu
authors.forename: Lu
authors.initials: L
authors.lastname: Zhang
authors.forename: Shibin
authors.initials: S
authors.lastname: He
authors.forename: Min
authors.initials: M
authors.lastname: Huang
authors.forename: Junjun
authors.initials: J
authors.lastname: Tan
authors.forename: Lin
authors.initials: L
authors.lastname: Zhao
authors.forename: Shihan
authors.initials: S
authors.lastname: Yan
authors.forename: Hui
authors.initials: H
authors.lastname: Li
authors.forename: Kun
authors.initials: K
authors.lastname: Zhou
authors.forename: Yanan
authors.initials: Y
authors.lastname: Liang
authors.forename: Lijia
authors.initials: L
authors.lastname: Li
mesh_terms: D042002:Chromatin Assembly and Disassembly; D047369:Chromatin Immunoprecipitation; D003080:Cold Temperature; D019175:DNA Methylation; D018744:DNA, Plant / Q000378:metabolism; D020868:Gene Silencing; D017343:Genes, Plant; D006570:Heterochromatin / Q000737:chemistry / Q000378:metabolism*; D006657:Histones / Q000235:genetics / Q000378:metabolism*; D013312:Stress, Physiological; D020080:Tandem Repeat Sequences; D015533:Transcriptional Activation; D003313:Zea mays / Q000235:genetics / Q000378:metabolism / Q000502:physiology
chemical_list: D018744:DNA, Plant; D006570:Heterochromatin; D006657:Histones