XVI International Botanical Congess

Two-hybrid screens allowed the isolation of novel cell cycle regulators, amongst which CKIs and a novel D-type cyclins. In situ hybridisations showed that the novel D-type cyclin has a central role in allowing cells to re-enter the cell cycle. Plants contain two classes of CDKs. A first class comprises CDKs that contain the PSTAIRE amino-acid motif and are constitutively expressed during the cell cycle. The second class of CDKs contains the PPTALRE or PPTTLRE motif. Transgenic tobacco plants overproducing dominant negative CDKs demonstrate that the PSTAIRE containing CDKs control both the G1/S and G2/M transitions, while the other class of CDKs solely regulate the G2/M transition.