| Just before mitosis, a band of microtubules and actin, called the preprophase band, forms around the cell at its midline. The preprophase band disappears as the cell reaches metaphase, but its position at the cortex remains marked and will determine the future site of division. After anaphase, the microtubules of the spindle form the phragmoplast. These microtubules serve as tracks on which membrane vesicles are carried to the middle of the cell from the Golgi apparatus. These vesicles contain the various glycoproteins and other components that will form the new cell wall. Vesicle fusion results in the formation of a disc-shaped membrane compartment called the cell plate, which expands outward until it eventually contacts and fuses with the cell membrane, thereby separating the daughter cells. A new cell wall is then completed between the daughter cell membranes. |
