The Arabidopsis D-type cyclin CYCD2;1 and the inhibitor ICK2/KRP2 modulate auxin-induced lateral root formation

Luis Sanz, Walter Dewitte, Celine Forzani, Farah Patell, Jeroen Nieuwland, Bo Wen, Pedro Quelhas, Sarah De Jager, Craig Titmus, Aurélio Campilho, Hong Ren, Mark Estelle, Hong Wang, James A H Murray

Research output: Contribution to journalArticlepeer-review


The integration of cell division in root growth and development requires mediation of developmental and physiological signals through regulation of cyclin-dependent kinase activity. Cells within the pericycle form de novo lateral root meristems, and D-type cyclins (CYCD), as regulators of the G₁-to-S phase cell cycle transition, are anticipated to play a role. Here, we show that the D-type cyclin protein CYCD2;1 is nuclear in Arabidopsis thaliana root cells, with the highest concentration in apical and lateral meristems. Loss of CYCD2;1 has a marginal effect on unstimulated lateral root density, but CYCD2;1 is rate-limiting for the response to low levels of exogenous auxin. However, while CYCD2;1 expression requires sucrose, it does not respond to auxin. The protein Inhibitor-Interactor of CDK/Kip Related Protein2 (ICK2/KRP2), which interacts with CYCD2;1, inhibits lateral root formation, and ick2/krp2 mutants show increased lateral root density. ICK2/KRP2 can modulate the nuclear levels of CYCD2;1, and since auxin reduces ICK2/KRP2 protein levels, it affects both activity and cellular distribution of CYCD2;1. Hence, as ICK2/KRP2 levels decrease, the increase in lateral root density depends on CYCD2;1, irrespective of ICK2/CYCD2;1 nuclear localization. We propose that ICK2/KRP2 restrains root ramification by maintaining CYCD2;1 inactive and that this modulates pericycle responses to auxin fluctuations.

Original languageEnglish
Pages (from-to)641-60
Number of pages20
JournalThe Plant cell
Issue number2
Publication statusPublished - Feb 2011


  • Arabidopsis
  • Arabidopsis Proteins
  • Cell Cycle
  • Cell Cycle Proteins
  • Cell Nucleus
  • Cyclins
  • Gene Expression Regulation, Plant
  • Indoleacetic Acids
  • Mutation
  • Plant Roots
  • Proteasome Endopeptidase Complex


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