We present evidence to show that the KEULE gene of Arabidopsis is invo
lved in cytokinesis. Mutant kettle embryos have large multinucleate ce
lls with gapped or incomplete cross walls, as well as cell wall. stubs
that are very similar to those observed upon caffeine inhibition of c
ytokinesis in plants. These defects are observed in all populations of
dividing cells in the mutant, including calli, but less frequently in
mature cells. Cell division appears to be slowed down, and the planes
of cell division are often misoriented. In late embryos and seedlings
, cross-wall formation usually appears complete, suggesting that the r
equirement for KEULE during cytokinesis is not absolute. Nonetheless,
kettle mutants die as seedlings with large polyploid cells. The bloate
d surface layer of kettle seedlings does not uniformly behave like wil
d-type epidermis, and patches of this layer assume characteristics of
the underlying ground tissue. The cytokinesis defect of kettle mutants
may influence aspects of cellular differentiation.