Abstract

Histone phosphorylation is dynamically regulated during cell division, such as H3 -Ser10, H3-Thr11 and H3-Ser28. Here we analyzed maize (Zea mays L) for Thr133-phosphorylated Histone H2A, which is important for spindle checkpoint control and centromere cohesion protector Shugoshin localization in mammals and yeast. Immunostaining results indicate that ph-H2A-Thr133 signals bridged those of CENH3 by using a plant displaying YFP-CENH3 signals. H2A-Thr133 is phosphorylated in different cell types. During mitosis, H2A Thr133 phosphorylation becomes strong in metaphase and is specific to centromere regions but drops during later anaphase and telophase. Immunostaining for several maize dicentric chromosomes revealed that the inactive centromeres have lost the phosphorylation of H2A-Thr133. During meiosis in maize meiocytes, H2A phosphorylation becomes strong in the early pachytene stage and increases to a maximum at metaphase I. In the maize meiotic mutant, afd1 (absence of first division), sister chromatids show equational separation at metaphase I, but there is no H2A-Thr-133 phosphorylation changes during meiosis compared with wild type. In sgo1 mutants, sister chromatid segregate randomly during meiosis II, phosphorylation of H2A-Thr-133 is observed on the centromere regions during meiosis II. The availability of these mutants in maize that lack sister cohesion and Shugoshin indicate that the signals for phosphorylation are not dependent on cohesion but on centromere activity.