Division plane orientation in plant cells

Abstract

This review discusses current knowledge on division plane determination in plant cells and how division within this plane is executed during cytokinesis. Plants cells are unusual among eukaryotes in that their planes of division are established prior to the onset of mitosis. Factors that contribute to the initial selection of the division plane include extra-cellular signals, cell geometry and polarity, and nuclear position. During the G2 phase of the cell cycle, the formation of the preprophase band (PPB), a cortical assembly of microtubules and microfilaments, signals the future location of the division plane. Factors important for PPB formation and maturation include the actin cytoskeleton, changes in microtubule dynamics, and protein dephosphorylation. Prior to its disassembly at prometaphase, the PPB functions in more than one way to determine subsequent placement of the new cell wall. First, the PPB influences the initial orientation of the spindle, which facilitates subsequent cell wall formation within the division plane. Second, the PPB is thought to direct the formation of a cortical division site that persists after PPB breakdown and interacts during cytokinesis with the expanding phragmoplast, a cytoskeletal assembly that directs the deposition of the partitioning cell wall. Both negative and positive cortical markers are implicated in maintaining the memory of the former PPB site throughout mitosis and cytokinesis. © 2008 Springer-Verlag Berlin Heidelberg.