Phosphoregulation of Microtubule Assembly and Disassembly for Phragmoplast Expansion During Plant Cytokinesis

Plant cytokinesis results in the formation of the cell plate by the phragmoplast which contains dynamic microtubules serving as the track for the delivery of cell wall builders included in Golgi vesicles. During the centrifugal process of cell plate assembly, new microtubules are assembled and bundled at the leading edge to prepare for vesicle transport while older microtubules are disassembled at the lagging edge upon the completion of vesicle delivery. The turnover of phragmoplast microtubules in this process is thought to be regulated by phosphorylation of the key microtubule bundling factor MAP65. A recent study revealed a surprising role of the α-Aurora kinase, which is typically known for its role in governing the formation of the bipolar spindle apparatus, in phosphorylating the primary microtubule bundler MAP65-3 in Arabidopsis. This phosphorylation positively contributes to the expansion of the phragmoplast. The phragmoplast midzone is also the hub for other cytokinesis-important kinases. It is intriguing how these kinases are targeted and how they may crosstalk with each other to orchestrate the expansion of the phragmoplast.