Cyclin-dependent kinase-activating kinases CDKD;1 and CDKD;3 are essential for preserving mitotic activity in Arabidopsis thaliana.
For the full activation of cyclin-dependent kinases (CDKs), not only cyclin binding but also CDK phosphorylation is required. This activating phosphorylation is mediated by CDK-activating kinases (CAKs). Arabidopsis has four genes showing similarity to vertebrate-type CAKs, three CDKDs (CDKD;1-CDKD;3) and one CDKF (CDKF;1). We previously found that the cdkf;1 mutant is defective in post-embryonic development, even though the kinase activities of core CDKs remain unchanged relative to the wild type. This raised a question about the involvement of CDKDs in CDK activation in planta. Here we report that the cdkd;1 cdkd;3 double mutant showed gametophytic lethality. Most cdkd;1-1 cdkd;3-1 pollen grains were defective in pollen mitosis I and II, producing one-cell or two-cell pollen grains that lacked fertilization ability. We also found that the double knock-out of CDKD;1 and CDKD;3 caused arrest and/or delay in the progression of female gametogenesis at multiple steps. Our genetic analyses revealed that the functions of CDKF;1 and CDKD;1 or CDKD;3 do not overlap, either during gametophyte and embryo development or in post-embryonic development. Consistent with these analyses, CDKF;1 expression in the cdkd;1-1 cdkd;3-1 mutant could not rescue the gametophytic lethality. These results suggest that, in Arabidopsis, CDKD;1 and CDKD;3 function as CAKs controlling mitosis, whereas CDKF;1 plays a distinct role, mainly in post-embryonic development. We propose that CDKD;1 and CDKD;3 phosphorylate and activate all core CDKs, CDKA, CDKB1 and CDKB2, thereby governing cell cycle progression throughout plant development.
Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara, 630-0192, Japan.
Hirotomo
H
Takatsuka
Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara, 630-0192, Japan.
Chikage
C
Umeda-Hara
Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara, 630-0192, Japan.|JST, CREST, 8916-5 Takayama, Ikoma, Nara, 630-0192, Japan.
Masaaki
M
Umeda
D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D018844:Cyclin-Dependent Kinases / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D008938:Mitosis; D009154:Mutation; D056771:Ovule / Q000235:genetics; D010766:Phosphorylation; D030821:Plants, Genetically Modified; D011058:Pollen / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D012639:Seeds / Q000235:genetics
D029681:Arabidopsis Proteins; C112244:Cak1at protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases; C523216:CDKC;1 protein, Arabidopsis; C000610748:CDKD;3 protein, Arabidopsis; D018844:Cyclin-Dependent Kinases
Arabidopsis thaliana; CDK-activating kinase; cell cycle; cyclin-dependent kinase; gametogenesis