title: Epigenetic regulation of repetitive elements is attenuated by prolonged heat stress in Arabidopsis.
abstract: Epigenetic factors determine responses to internal and external stimuli in eukaryotic organisms. Whether and how environmental conditions feed back to the epigenetic landscape is more a matter of suggestion than of substantiation. Plants are suitable organisms with which to address this question due to their sessile lifestyle and diversification of epigenetic regulators. We show that several repetitive elements of Arabidopsis thaliana that are under epigenetic regulation by transcriptional gene silencing at ambient temperatures and upon short term heat exposure become activated by prolonged heat stress. Activation can occur without loss of DNA methylation and with only minor changes to histone modifications but is accompanied by loss of nucleosomes and by heterochromatin decondensation. Whereas decondensation persists, nucleosome loading and transcriptional silencing are restored upon recovery from heat stress but are delayed in mutants with impaired chromatin assembly functions. The results provide evidence that environmental conditions can override epigenetic regulation, at least transiently, which might open a window for more permanent epigenetic changes.
authors.affiliation: Gregor Mendel Institute of Molecular Plant Biology, Austrian Academy of Sciences, 1030 Viena, Austria.
authors.forename: Ales
authors.initials: A
authors.lastname: Pecinka
authors.forename: Huy Q
authors.initials: HQ
authors.lastname: Dinh
authors.forename: Tuncay
authors.initials: T
authors.lastname: Baubec
authors.forename: Marisa
authors.initials: M
authors.lastname: Rosa
authors.forename: Nicole
authors.initials: N
authors.lastname: Lettner
authors.forename: Ortrun
authors.initials: O
authors.lastname: Mittelsten Scheid
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000502:physiology; D019175:DNA Methylation; D018744:DNA, Plant / Q000378:metabolism; D044127:Epigenesis, Genetic; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D020868:Gene Silencing; D018869:Heat-Shock Response; D006570:Heterochromatin / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D006358:Hot Temperature; D009707:Nucleosomes / Q000378:metabolism; D012091:Repetitive Sequences, Nucleic Acid; D014158:Transcription, Genetic; D015533:Transcriptional Activation
chemical_list: D018744:DNA, Plant; D006570:Heterochromatin; D006657:Histones; D009707:Nucleosomes