The Role of Endocytosis in the Creation of the Cortical Division Zone in Plants

Control of the pattern of cell division is essential for the proper development of multicellular organisms. In animal cells, cytokinesis is mediated by a contractile ring in which the cleavage force is produced by an acto-myosin system. Furthermore, the future site of cell division in animal cells (the site where contraction starts in the cell cortex) is determined by the position of the aster during the later stages of mitosis. In contrast, plant cytokinesis involves the assembly of a cell plate from Golgi-derived vesicles. The division site in plants (the cell cortex where the cell plate fuses with the parental cell walls) is defined by a band of cortical microtubules (MTs) – the preprophase band (PPB) of MTs – that mark the division site during prophase. The PPB MTs subsequently disassemble when the cells enter prometaphase. However, some positional information, or positional memory, is retained in the cell cortex/plasma membrane where the PPB of MTs was located, and the cell plate edge grows towards and fuses with this predetermined division site. Thus, how MTs demarcate the future division site during PPB development, and how the division site memory is created and maintained in the PPB region until the end of cytokinesis, are important questions related to the regulation of division plane positioning in plants.