Genetic dissection of cytokinesis

Higher plants have evolved specific mechanisms for partitioning the cytopla sm of dividing cells. In the predominant mode of phragmoplast-assisted cyto kinesis, a cell wall and flanking plasma membranes are made de novo from a transient membrane compartment, the cell plate, which in turn forms by vesi cle fusion from the centre to the periphery of the dividing cell. Other mod es of cytokinesis appear to occur in meiotic cells and developing gametophy tes. Here we review recent progress in the analysis of plant cytokinesis, f ocusing on genetic studies in Arabidopsis which are beginning to identify s tructural and regulatory components of phragmoplast-assisted cytokinesis. T wo classes of mutations have been described. In one class, the defects appe ar to be confined to cell plate formation, suggesting that the execution of cytokinesis is specifically affected. Mutations in the other class display more general defects in cell division. We also discuss possible roles of p roteins that have been localised in cytokinetic cells but not characterised genetically. Finally, mutations affecting meiotic or gametophytic cell div isions suggest that mechanistically different modes of cytokinesis occur in higher plants.