Activation of an alfalfa cyclin-dependent kinase inhibitor by calmodulin-like domain protein kinase

Aladár Pettkó-Szandtner, Tamás Mészáros, Gábor V. Horváth, László Bakó, Éva Csordás-Tóth, András Blastyák, Miroslava Zhiponova, Pál Miskolczi, Dénes Dudits

Research output: Contribution to journalArticle

43 Citations (Scopus)


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 (Medsaq2;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 G 1/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.

Original languageEnglish
Pages (from-to)111-123
Number of pages13
JournalPlant Journal
Issue number1
Publication statusPublished - Apr 1 2006


  • Abscisic acid
  • Ca signalling
  • Cell cycle
  • Cyclin-dependent kinase
  • Phosphorylation
  • Retinoblastoma-related protein

ASJC Scopus subject areas

  • Genetics
  • Plant Science
  • Cell Biology

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