Measurement of plant cyclin-dependent kinase activity using immunoprecipitation-coupled and affinity purification-based kinase assays and the baculovirus expression system.

Orderly progression of the eukaryotic cell cycle is governed by a coordinated response to intrinsic and extracellular cues through activation of cyclin-dependent kinases (CDKs). It is therefore important to verify the kinase activity of distinct types of CDKs during the cell cycle. The immunoprecipitation-coupled kinase assay is a useful procedure to evaluate CDK activity in vivo. Although a specific antibody is usually required for immunoprecipitation, transgenic plant cells expressing tag- or marker protein-fused CDKs are also suitable for this purpose. In addition, the baculovirus expression system is a valuable tool for analyzing CDK activity in vitro, because activation of CDKs is regulated by posttranscriptional modification systems that are active in the insect host cells.