Expression of a nondegradable cyclin B1 affects plant development and leads to endomitosis by inhibiting the formation of a phragmoplast.
In plants after the disassembly of mitotic spindle, a specific cytokinetic structure called the phragmoplast is built, and after cytokinesis, microtubules populate the cell cortex in an organized orientation that determines cell elongation and shape. Here, we show that impaired cyclin B1 degradation, resulting from a mutation within its destruction box, leads to an isodiametric shape of epidermal cells in leaves, stems, and roots and retarded growth of seedlings. Microtubules in these misshaped cells are grossly disorganized, focused around the nucleus, whereas they were entirely missing or abnormally organized along the cell cortex. A high percentage of cells expressing nondestructible cyclin B1 had doubled DNA content as a result of undergoing endomitosis. During anaphase the cytokinesis-specific syntaxin KNOLLE could still localize to the midplane of cell division, whereas NPK1-activating kinesin-like protein 1, a cytokinetic kinesin-related protein, was unable to do so, and instead of the formation of a phragmoplast, the midzone microtubules persisted between the separated nuclei, which eventually fused. In summary, our results show that the timely degradation of mitotic cyclins in plants is required for the reorganization of mitotic microtubules to the phragmoplast and for proper cytokinesis. Subsequently, the presence of nondegradable cyclin B1 leads to a failure in organizing properly the cortical microtubules that determine cell elongation and shape.
Max Planck Institute of Molecular Plant Physiology, 14476 Golm, Germany.
Magdalena
M
Weingartner
Marie-Claire
MC
Criqui
Tamás
T
Mészáros
Pavla
P
Binarova
Anne-Catherine
AC
Schmit
Anne
A
Helfer
Aude
A
Derevier
Mathieu
M
Erhardt
László
L
Bögre
Pascal
P
Genschik
D001483:Base Sequence; D002455:Cell Division; D019926:Cyclin B / Q000235:genetics / Q000378:metabolism*; D056744:Cyclin B1; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D018744:DNA, Plant / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D017343:Genes, Plant; D008870:Microtubules / Q000378:metabolism; D008938:Mitosis; D009154:Mutation; D010641:Phenotype; D010940:Plant Proteins / Q000378:metabolism; D030821:Plants, Genetically Modified; D011123:Polyploidy; D036226:Seedlings / Q000378:metabolism; D008941:Spindle Apparatus / Q000378:metabolism; D014026:Nicotiana / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*
D019926:Cyclin B; D056744:Cyclin B1; D018744:DNA, Plant; D010940:Plant Proteins; D018844:Cyclin-Dependent Kinases