Inhibition of protein synthesis during G2 induces irregular metaphase and anaphase in mitosis of root cells of Allium sativum L.

When partially synchronized root tip cells of Allium sativum L. (Garlic) were treated with cycloheximide during G2, some cells showed condensed chromosomes in arrested prophase nuclei. Other cells that were able to proceed into metaphase exhibited abnormal alignments of chromosomes at the metaphase plate, resulting in irregular anaphase and telophase movements of the chromosomes. Electron microscopy showed that kinetochores were poorly developed with only few kinetochore-to-pole microtubules attached. Other microtubules, probably mostly pole-to-pole microtubules, exhibited irregular pathways making the spindle appear disorganized. These observations seem to suggest that a protein (or proteins) necessary for kinetochore and spindle function are synthesized at a time in G2 similar to the synthesis of the mitotic proteins that are necessary for chromosome condensation and nuclear membrane breakdown. It is suggested that the protein(s) needed for normal spindle function are newly synthesized during each cell cycle and therefore belong functionally to the mitotic proteins.