Protein kinase activity in CDKA– or CDKB1;1–D-type cyclin complexes during maize germination. Activity was measured in CDKA–D-type cyclins or CDKB1;1–D-type cyclins complexes at 0, 6, 12, 18, and 24h of germination. (A, B) Kinase activity corresponding to CycD2;2 associated with CDKA or CDKB1,1 respectively. (C, D) Kinase activity corresponding to CycD4;2 associated with CDKA or CDKB1,1 respectively. (E, F) Kinase activity corresponding to CycD5;3 associated with CDKA or CDKB1,1 respectively. Again, in (F), the intensity of the band at 24h was taken as 1 as it could not be referred to the null value at time 0. The amount of GST–RBR protein (37kDa) added as a substrate for kinase activity was used as the loading control. Densitometry analysis was performed relating band intensity of all samples to intensity of the loading control and then to the dry seed band. C(+), Kinase activity in cyclin–CDK complexes pulled-down by rice CKS protein; C(−), D-type cyclin–CDK complexes without RBR added. Each bar represents the mean±SE from three independent experiments. *Statistically significant value (P<0.001) compared to control.