HISTONE H4 UNDERACETYLATION IN PLANT FACULTATIVE HETEROCHROMATIN

It has been recently shown that facultative heterochromatin in some ph yla is H4 and H3 histone underacetylated, Here we present H4 acetylati on analyses in a monocotyledonous plant species, Gagea lutea, whose pe ntaploid endosperm nuclei possess prominent facultative heterochromati n regions, This heterochromatin is attributed to three chromosome sets originated from the chalazal polar nucleus of the embryo sac, We have previously shown that some parts of this heterochromatin contain heav ily methylated DNA, but not all the heterochromatin is hypermethylated , In this report we demonstrate that this facultative heterochromatin is characterised by a conspicuous depletion of histone H4 acetylation at N-terminal lysine residues 5, 8, and 12, but not 16, Endosperm meta phases stained with antiserum against H4Ac5 indicated some heavily lab elled chromosomes, while the others displayed no signal (presumably th ose coming from the three heterochromatinised chromosome sets). Wester n blotting analyses have shown that the antisera used, designed to det ect human H4 histones, are suitable to recognise specific isoforms of acetylated H4 histones in plants and that the most abundant H4 in G. l utea leaves occurs in its diacetylated isoform, We conclude that flowe ring plants, similarly to protozoa, yeasts and animals, evolved core h istone acetylation/deacetylation as a long-term transcriptional contro l mechanism to establish and/or transmit epigenetic information on gen e expression.