The cell cycle dependent phosphorylation of histone H3 is correlated with the condensation of plant mitotic chromosomes

Mitotically dividing cells of Secale cereale, Hordeum vulgare and Vicia fab a were studied ny indirect immunofluorescence using an antibody recognizing phosphorylated histone H3. The study revealed the following features: (i) the H3 phosphorylation starts at prophase and ends at telophase in the peri centromeric chromatin, is associated with the condensation of mitotic chrom osomes and is independent of the distribution Of late replicating heterochr omatin. (ii) Compared with other chromosome regions, the pericentromeric ch romatin is histone H3 hyperphosphorylated. (iii) The study of a semi-dicent ric chromosome revealed that only at intact centromeres is the chromatin hy perphosphorylated at H3.