Cytoskeletal Motor Proteins in Plant Cell Division.

Plant cell division involves anastral spindles with incompletely focused poles and the phragmoplast with antiparallel microtubules. The organization of the spindle microtubule array and the phragmoplast array is thought to be dependent on microtubule-based motor kinesins. Among the more than 50 kinesins encoded by a single plant genome, a number of them are either proven or predicted to be essential for cell division. Members of the Kinesin-14 subfamily play a critical role in organizing spindle poles. Some kinesins yet to be identified could be required for facilitating nuclear envelope breakdown at the end of prophase, and others for mediating the interaction between chromosomes and microtubules for spindle assembly. During anaphase, the disassembly of kinetochore fibers and the accompanying sister chromatid movement would definitely be assisted by kinesins. Similarly to fungi and animals, plants likely use Kinesin-5 for microtubule sliding, leading to spindle elongation. During cytokinesis, Kinesin-12 is required for establishing the antiparallel fashion of the phragmoplast microtubule array. Microtubule turnover in this highly dynamic array also depends on plant-specific kinesins acting on an MAP kinase cascade. More than one kinesin is predicted to deliver vesicles for cell plate assembly. Lastly, recent data also suggest that kinesins play a critical role in spatial regulation of cytokinesis. Very little has been learned about the potential roles of myosins in plant cell division. Whether myosins are also involved in vesicle transport in the phragmoplast awaits further examination. We can conclude that splendid cytoskeletal motors play splendid roles in plant cell division. [ABSTRACT FROM AUTHOR]