LAUSR

The special and temporal distribution of several posttranslational histone modifications (H3K4me2, H3K4me3, H3K9me2, H3K27me2, H3K9ac, H3K14ac, H3K18ac, H3K27ac, H3S10ph, H3S28ph, H3T3ph, H3K4me1-H3T3ph, H3K4me3/H3T3ph H3T11ph, H2AT121ph, and H2A.XS139ph) has been analysed during microsporogenesis of tobacco. Homogeneous distribution of the euchromatin marks H3K4me2 and H3K4me3 throughout the entire chromatin of amphidiploid Nicotiana tabacum suggests that both subgenomes were transcriptionally active. Localization of hyperacetylated clusters of H3K18 and H3K27 close to nucleoli suggests that both modifications were possibly involved in transcription of the 45S rDNA. A subset of chromosomes showed clusters of hypermethylated H3K9me2 and H3K27me2 regions. The cell-cycle dependent phosphorylation of histone H3 during meiosis revealed a high conservation compared to other plant species. In addition to meiotic prophase I, we observed phospho-H2A.X signals during the second stage of meiosis in N. tabacum.