DOMINANT-NEGATIVE MUTANTS OF THE CDC2 KINASE UNCOUPLE CELL-DIVISION FROM ITERATIVE PLANT DEVELOPMENT

Because plant cells do not move and are surrounded by a rigid cell wal l, cell division rates and patterns are believed to be directly respon sible for generating new structures throughout development, To study t he relationship between cell division and morphogenesis, transgenic to bacco and Arabidopsis plants were constructed expressing dominant muta tions in a key regulator of the Arabidopsis cell cycle, the Cdc2a kina se, Plants constitutively overproducing the wild-type Cdc2a or the mut ant form predicted to accelerate the cell cycle did not exhibit a sign ificantly altered development, In contrast, a mutation expected to arr est the cell cycle abolished cell division when expressed in Arabidops is, whereas some tobacco plants constitutively producing this mutant p rotein were recovered. These plants had a reduced histone H1 kinase ac tivity and contained considerably fewer cells, These cells were, howev er, much larger and underwent normal differentiation, Morphogenesis, h istogenesis and developmental timing were unaffected. The results indi cate that, in plants, the developmental controls defining shape can ac t independently from cell division rates.