Involvement of the mitogen-activated protein kinase SIMK in regulation of root hair tip growth

Jozef Šamaj, Miroslav Ovecka, Andrej Hlavacka, Fatma Lecourieux, Irute Meskiene, Irene Lichtscheidl, Peter Lenart, Ján Salaj, Dieter Volkmann, László Bögre, František Baluška, Heribert Hirt

Research output: Contribution to journalArticlepeer-review

134 Scopus citations


Mitogen-activated protein kinases (MAPKs) are involved in stress signaling to the actin cytoskeleton in yeast and animals. We have analyzed the function of the stress-activated alfalfa MAP kinase SIMK in root hairs. In epidermal cells, SIMK is predominantly nuclear. During root hair formation, SIMK was activated and redistributed from the nucleus into growing tips of root hairs possessing dense F-actin meshworks. Actin depolymerization by latrunculin B resulted in SIMK relocation to the nucleus. Conversely, upon actin stabilization with jasplakinolide, SIMK co-localized with thick actin cables in the cytoplasm. Importantly, latrunculin B and jasplakinolide were both found to activate SIMK in a root-derived cell culture. Loss of tip-focused SIMK and actin was induced by the MAPK kinase inhibitor UO 126 and resulted in aberrant root hairs. UO 126 inhibited targeted vesicle trafficking and polarized growth of root hairs. In contrast, overexpression of gain-of-function SIMK induced rapid tip growth of root hairs and could bypass growth inhibition by UO 126. These data indicate that SIMK plays a crucial role in root hair tip growth.

Original languageEnglish (US)
Pages (from-to)3296-3306
Number of pages11
Issue number13
StatePublished - Jul 1 2002
Externally publishedYes


  • Actin cytoskeleton
  • MAP kinase
  • Root hairs
  • Signaling
  • Tip growth

ASJC Scopus subject areas

  • General Neuroscience
  • Molecular Biology
  • General Biochemistry, Genetics and Molecular Biology
  • General Immunology and Microbiology


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