Activation of an alfalfa cyclin-dependent kinase inhibitor by calmodulin-like domain protein kinase.
Kip-related proteins (KRPs) play a central role in the regulation of the cell cycle and differentiation through modulation of cyclin-dependent kinase (CDK) functions. We have identified a CDK inhibitor gene from Medicago truncatula (Mt) by a yeast two-hybrid screen. The KRPMt gene was expressed in all plant organs and cultured cells, and its transcripts accumulated after abscisic acid and NaCl treatment. The KRPMt protein exhibits seven conserved sequence domains and a PEST motif that is also detected in various Arabidopsis KRPs. In the yeast two-hybrid test, the KRPMt protein interacted with CDK (Medsa;CDKA;1) and D-type cyclins. However, in the pull-down assays, B-type CDK complexes were also detectable. Recombinant KRPMt differentially inhibited various alfalfa CDK complexes in phosphorylation assays. The immunoprecipitated Medsa;CDKA;1/A;2 complex was strongly inhibited, whereas the mitotic Medsa;CDKB2;1 complex was the most sensitive to inhibition. Function of Medsa;CDKB1;1 complex was not inhibited by the KRPMt protein. The mitotic Medsa;CYCB2 and Medsa;CYCA2;1 complexes responded weakly to this inhibitor protein. Kinase complexes from G2/M cells showed increased sensitivity towards the inhibitor compared with those isolated from G1/S-phase cells. In vitro phosphorylation of Medicago retinoblastoma-related protein was also reduced in the presence of KRPMt. Phosphorylation of this inhibitor protein by the recombinant calmodulin-like domain protein kinase (MsCPK3) resulted in enhanced inhibition of CDK function. The data presented emphasize the selective sensitivity of various cyclin-dependent kinase complexes to this inhibitor protein, and suggest a role for CDK inhibitors and CPKs in cross-talk between Ca2+ signalling and regulation of cell-cycle progression in plants.
Institute of Plant Biology, Biological Research Centre, Hungarian Academy of Sciences, Szeged, H-6726, Temesvári krt. 62, Hungary.
Aladár
A
Pettkó-Szandtner
Tamás
T
Mészáros
Gábor V
GV
Horváth
László
L
Bakó
Eva
E
Csordás-Tóth
András
A
Blastyák
Miroslava
M
Zhiponova
Pál
P
Miskolczi
Dénes
D
Dudits
D000040:Abscisic Acid / Q000494:pharmacology; D020816:Amino Acid Motifs; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000737:chemistry; D002453:Cell Cycle / Q000502:physiology; D003001:Cloning, Molecular; D050756:Cyclin-Dependent Kinase Inhibitor Proteins / Q000235:genetics / Q000378:metabolism*; D016213:Cyclins / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D000455:Medicago sativa / Q000201:enzymology* / Q000235:genetics; D046913:Medicago truncatula / Q000201:enzymology* / Q000235:genetics; D008969:Molecular Sequence Data; D010766:Phosphorylation; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction; D012965:Sodium Chloride / Q000494:pharmacology
D002147:Calmodulin; D050756:Cyclin-Dependent Kinase Inhibitor Proteins; D016213:Cyclins; D018076:DNA, Complementary; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D012965:Sodium Chloride; D000040:Abscisic Acid; D011494:Protein Kinases; D002118:Calcium