15th International Conference on Arabidopsis Research - TAIR

T03-063
CDKA;1 is essential for Arabidopsis embryo and
gametophyte development
Moritz Nowack(1), Paul Grini(2), Marcel Lafos(3), Csaba Koncz(3), Arp Schnittger(1)
1-Unigruppe am Max-Planck-Institut für Züchtungsforschung, Lehrstuhl für Botanik III, Universität
zu Köln, Carl-von-Linné-Weg 10, 50829 Köln, Germany
2-Department of Molecular Biosciences, University of Oslo, P.O.Box 1031 Blindern, N-0315 Oslo,
Norway
3-Max-Planck-Institut für Züchtungsforschung, Carl-von-Linné-Weg 10, 50829 Köln, Germany
As in other eukaryotes, in plants progression through the cell cycle is
controlled by cyclin dependent kinases (CDKs). The kinase activity of CDKs
depends on the binding to diverse cyclins and can be further modulated by a
variety of regulator proteins, such as CDK inhibitors ICK/KRPs.
In yeast and in animals, the isolation and analysis of mutants has been
proven to be a powerful tool to understand cell cycle control. In Arabidopsis
however, mutational analyses of core cell cycle genes are largely missing.
From different T-DNA mutant collections we identified two potential CDKA;1
mutant lines. Both T-DNA insertions disrupt the protein structure and should
abolish kinase activity. Whereas the heterozygous cdka;1 mutant plants showed
no morphological deviations from wild type, homozygous mutants could
not be recovered. The latter argues for an essential role of CDKA;1 in early
Arabidopsis development. Consistent with this, arrested embryos were found
in the offspring of heterozygous mutant individuals. In addition, gametophytic
development seems to be affected.
T03 Cell Biology
T03-064
Study of the Arabidopsis ORC subunits during the
cell cycle and plant development
Sara Diaz-Triviño(1), Mar Castellano(1), Mari-Paz Sanchez(1), Crisanto Gutierrez(1)
1-Centro de Biología Molecular “Severo Ochoa”, CSIC-UAM, Universidad Autónoma de Madrid,
Cantoblanco, 28049 Madrid, Spain
Meristem are the main proliferative tissues in plants, being the source of new
cells for differentiation. In plants, almost all the differentiation is post-embrionic,
and all the adult tissues come from the undifferentiated meristematic
cells. Therefore, it is conceivable that alteration in meristematic cell division,
also affects plant development.
Here we study the mechanisms invovled in controlling cell cycle progression,
with a focus on the onset of S-phase. To this end, we are investigating the
regulation of the pre-replicative complexes, wich are formed by a heterohexameric
complex called ORC (origin recognition complex), CDC6, CDT1 and
MCMs. In this work we found that in Arabidopsis cultured cells the expression
of Arabidopsis ORC genes is regulated during the cell cycle. In the plant,
expresion of all ORC genes is more abundant in flowers. Arabidopsis is
unique in having two ORC1 genes (a and b). Interestingly these genes seem
to have a different regulation at the transcriptional level. AtORC1a mRNA is
more abundant in the aerial parts of dark grown seedlings while AtORC1b is
equally expressed in light and dark grown seedlings. We also have obtained
results of the interaction of different ORC subunits.
15 th <strong>International</strong> <strong>Conference</strong> on Arabidopsis Research 2004 · Berlin