Distribution of eu- and heterochromatin in Plantago ovata

Plantago ovata (2n = 8) is the only cultivated species in the monotypic genus Plantago. The seed husk of the plant constitutes the psyllium (Isabgol) which has many medicinal properties. The 1C DNA content was determined to be 0.635 pg (621 Mb) with an AT content of 59.7%. Applying Giemsa C-banding and fluorescence in situ hybridization (FISH) using the Cot-1 fraction of DNA on prometaphase and metaphase chromosomes we investigated the chromosomal distribution of eu- and heterochromatin. All applied techniques revealed that the euchromatin is located at the distal ends of all chromosome arms, besides the NOR-bearing ones. Interestingly, in addition one arm of chromosome 1 seems to be entirely euchromatic. Furthermore, we have analysed the correlation between the global distribution of histone H3 mono-, di- or trimethylated at either lysine 4, 9 or 27 and the microscopically detectable eu- and heterochromatin. Methylated H3K4 was found to be enriched exclusively within euchromatin. From the other tested methylation marks only H3K9me1, H3K9me2 and H3K27me1 showed, in addition to a more or less disperse labelling, an enrichment within the heterochromatic chromocentres. The cell cycle dependent phosphorylation of histone H3 at serine 10 and threonine 11 was enriched in all pericentromeric regions.