Abstract
Cell division in basal land plants reveales a surprising variety of microtubule organizing centers (MTOCs) that is thought to represent milestones in the evolution of the typical diffuse acentrosomal plant MTOCs. In monoplastidic meiosis of the bryophytes, γ-tubulin is known to localize on the plastid surface in prophase and on the nuclear surface in telophase. As the membrane-based MTOC is not common in animal and seed plants, we further characterized these MTOCs in meiotic cells of the liverwort Dumortiera hirsuta using a drug study and in vitro experiments. γ-Tubulin localization patterns on plastid and nuclear surfaces are not affected by destruction of microtubules with oryzalin. γ-Tubulin is still detectable on the surface of isolated plastids and nuclei suggesting the tight association with nuclear and plastid envelope. In isolated platids, we could repolymerize microtubules from the plastids surface showing MTOC activities on the plastid surface.
