Division-plane orientation
Plants have a unique form of division: new cell wall construction starts in the middle of the cell and then expands outwards to the cortex. Although this mechanism is unique to plants, there are several important aspects, such as vesicle trafficking and antiparallel microtubule arrays, that are similar between plants and other eukaryotes.
How does the cytokinetic machinery reach the correct location at the cortex to divide the cell properly? Several lines of evidence suggest that the plant cell establishes the division site (the location where the cell will eventually divide) before the onset of mitosis. The location of the division is controlled by genetic factors, cell shape, and cell-cell interactions and mechanical properties, discussed in this review. The first obvious sign of the division site is the formation of a plant-specific microtubule and microfilament array called the preprophase band. During symmetric division, the preprophase band forms before prophase in a location to create two equally-sized daughter cells and then is disassembled when the spindle forms. After the chromosomes are separated, the cytokinetic machinery, composed of an antiparalllel microtubule array and microfilaments, serves as tracks for transport of vesicles containing cell wall building materials to the middle of the cell. This structure is known as the phragmoplast. The phragmoplast returns to the exact division site established by the preprophase band. The mechanisms underlying phragmoplast guidance to the division site are largely unknown, although recent insights into division plane maintenance are discussed here.
How does the cytokinetic machinery reach the correct location at the cortex to divide the cell properly? Several lines of evidence suggest that the plant cell establishes the division site (the location where the cell will eventually divide) before the onset of mitosis. The location of the division is controlled by genetic factors, cell shape, and cell-cell interactions and mechanical properties, discussed in this review. The first obvious sign of the division site is the formation of a plant-specific microtubule and microfilament array called the preprophase band. During symmetric division, the preprophase band forms before prophase in a location to create two equally-sized daughter cells and then is disassembled when the spindle forms. After the chromosomes are separated, the cytokinetic machinery, composed of an antiparalllel microtubule array and microfilaments, serves as tracks for transport of vesicles containing cell wall building materials to the middle of the cell. This structure is known as the phragmoplast. The phragmoplast returns to the exact division site established by the preprophase band. The mechanisms underlying phragmoplast guidance to the division site are largely unknown, although recent insights into division plane maintenance are discussed here.