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

Jozef Samaj1, Miroslav Ovecka, Andrej Hlavacka

  • 1Institute of Microbiology and Genetics, Vienna Biocenter, University of Vienna, Dr Bohrgasse 9, A-1030 Vienna, Austria.

The EMBO Journal
|July 3, 2002
PubMed

Insights

The stress-activated alfalfa MAP kinase SIMK is crucial for root hair growth. It relocates to growing tips and regulates actin cytoskeleton dynamics, essential for polarized growth.

Area of Science:

  • Plant Biology
  • Cell Signaling
  • Cytoskeleton Dynamics

Background:

  • Mitogen-activated protein kinases (MAPKs) mediate stress responses and actin cytoskeleton signaling in various organisms.
  • The specific role of stress-activated MAPKs in plant root hair tip growth remains largely unexplored.

Purpose of the Study:

  • To investigate the function of the stress-activated alfalfa MAP kinase SIMK in root hair tip growth.
  • To elucidate the relationship between SIMK, the actin cytoskeleton, and polarized growth in plant root hairs.

Main Methods:

  • Analysis of SIMK localization and activation in alfalfa root hairs under various conditions.
  • Treatment with actin depolymerizing (latrunculin B) and stabilizing (jasplakinolide) agents.
  • Inhibition of MAPK kinase using UO 126 and overexpression of a gain-of-function SIMK mutant.

Main Results:

  • SIMK is activated and relocates from the nucleus to the growing tips of root hairs, co-localizing with F-actin.
  • Actin depolymerization causes SIMK nuclear relocalization, while stabilization leads to cytoplasmic co-localization with actin cables.
  • SIMK activation is induced by latrunculin B and jasplakinolide.
  • Inhibition of SIMK signaling by UO 126 disrupts vesicle trafficking, polarized growth, and results in aberrant root hairs.
  • Overexpression of a gain-of-function SIMK mutant promotes rapid root hair tip growth and bypasses UO 126-induced inhibition.

Conclusions:

  • SIMK plays a critical role in regulating root hair tip growth by influencing actin cytoskeleton organization and polarized growth.
  • SIMK acts as a key signaling component linking external stimuli to the actin cytoskeleton, thereby controlling root hair morphogenesis.

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