Abstract
Cyclin-dependent protein kinases (CDKs) are main regulators during cell cycle. Here we show that CDKs might regulate the activation of NACK-PQR MAPK pathway that is known as a key-regulator of plant cytokinesis. The NACK-PQR pathway is activated by the direct interaction between NACK1 kinesin-like protein and NPK1 MAPKKK at anaphase. Previously we showed that both NACK1 and NPK1 are highly phosphorylated before the activation in vivo, and that they are phosphorylated by CDKs in vitvo. In this study, we show that NACK1 and NPK1 are phosphorylated at CDK-phosphorylation sites during early M phase when NPK1 are inactive. The levels of phosphorylation of NACK1 and NPK1 depended on the levels of CDK activities. In addition, the phosphorylation in vitro of NACK1 and NPK1 by CDKs inhibited the interaction between NACK1 and NPK1. These results suggest that CDKs function in suppression of the activation of NACK-PQR pathway, namely the entry of cytokinesis.
