title: Rumex acetosa Y chromosomes: constitutive or facultative heterochromatin?
abstract: Condensed Y chromosomes in Rumex acetosa L. root-tip nuclei were studied using 5-azaC treatment and immunohistochemical detection of methylated histones. Although Y chromosomes were decondensed within root meristem in vivo, they became condensed and heteropycnotic in roots cultured in vitro. 5-azacytidine (5-azaC) treatment of cultured roots caused transitional dispersion of their Y chromosome bodies, but 7 days after removal of the drug from the culture medium, Y heterochromatin recondensed and again became visible. The response of Rumex sex chromatin to 5-azaC was compared with that of condensed segments of pericentromeric heterochromatin in Rhoeo spathacea (Sw.) Steam roots. It was shown that Rhoeo chromocentres, composed of AT-rich constitutive heterochromatin, did not undergo decondensation after 5-azaC treatment. The Y-bodies observed within male nuclei of R. acetosa were globally enriched with H3 histone, demethylated at lysine 4 and methylated at lysine 9. This is the first report of histone tail-modification in condensed sex chromatin in plants. Our results suggest that the interphase condensation of Y chromosomes in Rumex is facultative rather than constitutive. Furthermore, the observed response of Y-bodies to 5-azaC may result indirectly from demethylation and the subsequent altered expression of unknown genes controlling tissue-specific Y-inactivation as opposed to the global demethylation of Y-chromosome DNA.
authors.affiliation: Department of Plant Cytology and Embryology, Institute of Botany, Jagiellonian University, Kraków, Poland.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Mosiołek
authors.forename: Paweł
authors.initials: P
authors.lastname: Pasierbek
authors.forename: Janusz
authors.initials: J
authors.lastname: Malarz
authors.forename: Maria
authors.initials: M
authors.lastname: Moś
authors.forename: Andrzej J
authors.initials: AJ
authors.lastname: Joachimiak
mesh_terms: D001374:Azacitidine / Q000494:pharmacology; D018929:Cell Culture Techniques; D002467:Cell Nucleus; D042002:Chromatin Assembly and Disassembly / Q000187:drug effects; D032461:Chromosomes, Plant / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D006570:Heterochromatin / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D006657:Histones / Q000378:metabolism; D018519:Meristem / Q000166:cytology; D008745:Methylation; D018517:Plant Roots / Q000166:cytology / Q000187:drug effects; D031804:Rumex / Q000166:cytology* / Q000235:genetics; D014998:Y Chromosome / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*
chemical_list: D006570:Heterochromatin; D006657:Histones; D001374:Azacitidine