Dominant negative mutants of the Cdc2 kinase uncouple cell division from iterative plant development.

Abstract

Because plant cells do not move and are surrounded by a rigid cell wall, cell division rates and patterns are believed to be directly responsible for generating new structures throughout development. To study the relationship between cell division and morphogenesis, transgenic tobacco and Arabidopsis plants were constructed expressing dominant mutations in a key regulator of the Arabidopsis cell cycle, the Cdc2a kinase. Plants constitutively overproducing the wild‐type Cdc2a or the mutant form predicted to accelerate the cell cycle did not exhibit a significantly altered development. In contrast, a mutation expected to arrest the cell cycle abolished cell division when expressed in Arabidopsis, whereas some tobacco plants constitutively producing this mutant protein were recovered. These plants had a reduced histone H1 kinase activity and contained considerably fewer cells. These cells were, however, much larger and underwent normal differentiation. Morphogenesis, histogenesis and developmental timing were unaffected. The results indicate that, in plants, the developmental controls defining shape can act independently from cell division rates.

The effect of the slow‐to‐green mutation on cell division during leaf initiation and early leaf growth in Lolium temulentum

“…Hence, cell division rate per se for the rapidly proliferating cells had no effect on the subsequent growth and development of the leaf primordium. This was also the case in transgenic tobacco plants expressing a dominant negative mutation of the cell division cycle gene, cdc2; the plants underwent normal development but the frequency of cell division was, apparently, reduced (Hemerly et al, 1995). At first glance, the data support the idea that the cell cycle and subsequent development are independent (Kaplan & Hagemann, 1991) and relate to an earlier finding in maize that eradicating division by gamma irradiation did not prevent embryos from initiating the first leaf (Foard, 1971).…”

Threshold level of protein kinase A activity and polarized growth in Mucor rouxii

“…These results indicate that in M. rouxii, differentiation and growth are two processes that are not linked. Studies from both plant systems and Drosophila indicate that there may be a weak link between cell-cycle progression and morphogenesis (Edgar & O'Farrell, 1989 ;Hemerly et al, 1995 ;Doerner et al, 1996), while recent studies in Aspergillus nidulans indicate an interaction between the two processes (Ye et al, 1999) …”

The Arabidopsis Auxin-Inducible Gene ARGOS Controls Lateral Organ Size

“…However, there are cases in which the alteration of cell proliferation is not correlated with changes in organ size. For example, expression of a dominant-negative Arabidopsis CDKA in transgenic tobacco results in almost normal-sized leaves with fewer but larger cells (Hemerly et al, 1995). In Arabidopsis, overexpression of CycD3;1 , a G1 cyclin gene, does not increase organ size but leads to a disturbed organogenesis, with numerous small, incompletely differentiated cells (Riou-Khamlichi et al, 1999;Dewitte et al, 2003).…”