CDKd3

CDKd3, also written as CDKD3 (cyclin-dependent kinase D3), is a serine/threonine protein kinase in plants and a member of the CDKD family that includes CDKD1 and CDKD2. CDKD proteins are homologous to CDK-activating kinases (CAKs) in other eukaryotes and are proposed to function as CAKs that activate other CDKs by phosphorylating their activation loop (the T-loop). In plants, CDKD kinases are also associated with the TFIIH transcription factor complex, contributing to transcription initiation and RNA polymerase II promoter clearance by phosphorylating components of the transcription machinery, including RNA Pol II CTD.

CDKd3 has been studied primarily in Arabidopsis thaliana, where it is expressed in developing tissues and overlaps with the other CDKDs. Functional analyses indicate that CDKD genes have partially redundant roles, with single mutants often showing mild phenotypes but compounded defects in combinations. Thus, CDKd3 participates in coordinating cell cycle progression with transcriptional regulation during plant development and in response to environmental cues. Orthologs of CDKd3 are present across plant species, reflecting the conserved nature of the CDKD/CAK module in plants.