Abstract
In angiosperms, mitosis and cytokinesis take place in the absence of structurally defined microtubule-organizing centers and the underlying mechanisms are largely unknown. In the spindle and phragmoplast, microtubule reorganization depends on microtubule-interacting factors like the γ-tubulin complex. Because of their critical functions in cell division, loss-of-function mutations in the corresponding genes are often homozygous or sporophytic lethal. However, a number of mutations like gem1, gcp2, and nedd1 can be maintained in heterozygous mutants in Arabidopsis thaliana. When mutant microspores produced by a heterozygous parent undergo pollen mitosis I, they are amenable for phenotypic characterization by fluorescence microscopy. The results would allow us to pinpoint at specific functions of particular proteins in microtubule reorganization that are characteristic to specific stages of mitosis and cytokinesis. Conclusions made in the developing microgametophytes can be extrapolated to somatic cells regarding mechanisms that regulate nuclear migration, spindle pole formation, phragmoplast assembly, and cell division plane determination.
Highlights
In angiosperms, mitosis and cytokinesis take place in the absence of structurally defined microtubule-organizing centers and the underlying mechanisms are largely unknown
Cytokinesis is brought about by the phragmoplast, an evolutionary landmark first appeared in advanced green algae (Pickett-Heaps, 1975; Graham et al, 2000), which gives rise to the cell plate resulted from the fusion of Golgi-derived vesicles
While some aspects of mitosis and cytokinesis are expected to be conserved in plant and animal cells (Lloyd and Chan, 2006), one should not anticipate that results of animal cell-based work would allow us to elucidate all molecular mechanisms that regulate plant cell division
Summary
Mitosis and cytokinesis take place in the absence of structurally defined microtubule-organizing centers and the underlying mechanisms are largely unknown. To date we only know functions of a handful of proteins that regulate MT organization in plant cells partly due to limited availability of homozygous mutants for corresponding genes. In many plants like lily, when the microsporocyte/microspore mother cell undergoes meiosis, successive cytokinesis takes place after each round of nuclear division.
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