Planta

, Volume 218, Issue 2, pp 276–287

The distributional changes and role of microtubules in Nod factor-challenged Medicago sativa root hairs

  • Ravisha R. Weerasinghe
  • David A. Collings
  • Eva Johannes
  • Nina Strömgren Allen
Original Article

DOI: 10.1007/s00425-003-1097-1

Cite this article as:
Weerasinghe, R.R., Collings, D.A., Johannes, E. et al. Planta (2003) 218: 276. doi:10.1007/s00425-003-1097-1

Abstract

The normal tip-growing pattern exhibited by root hairs of legumes is disrupted when the hair is exposed to Nod factors generated by compatible bacteria capable of inducing nodule formation. Since microtubules (MTs) play an important role in regulating directionality and stability of apical growth in root hairs [T.N. Bibikova et al. (1999) Plant J 17:657–665], we examined the possibility that Nod factors might affect the MT distribution patterns in root hairs of Medicago sativa L. We observed that Nod factor application caused rapid changes in the pattern of MTs starting as early as 3 min after perfusion. Within 3 to 10 min after Nod factor application, first endoplasmic and then cortical MTs depolymerised, initially at the proximal ends of cells. Twenty minutes after exposure to Nod factors, a transverse band of microtubules was seen behind the tip, while almost all other MTs had depolymerised. By 30 min, very few MTs remained in the root hair and yet by 1 h the MT cytoskeleton re-formed. When Nod factors were applied in the presence of 10 μM oryzalin or 5 μM taxol, the MTs appeared disintegrated while the morphological effects, such as bulging and branching, became enhanced. Compared to the treatments with oryzalin or taxol alone, the combinatory treatments exhibited higher growth rates. Since microtubule reorganization is one of the earliest measurable events following Nod factor application we conclude that microtubules have an important role in the early phases of the signalling cascade. Microtubule involvement could be direct or a consequence of Nod factor-induced changes in ion levels.

Keywords

NodulationNod factorMicrotubuleMedicagoRhizobium

Abbreviations

BNM

buffered nodulation medium

CLSM

confocal laser scanning microscopy

MT

microtubule

Supplementary material

Video S1 Depolymerization of cortical MTs in root hairs initiates in the locality of the nucleus 5 minutes after Nod factor treatment. A full stack extended focus projection was rotated and recorded as a movie using Leica TCS NT software

video1.mov (2 mb)
video1.mov (2.0 MB)

Video S2 An exceedingly concentrated band of MTs is seen behind the tip of the root hairs stimulated with Nod factors for 20 minutes. In the rotation, it is evident that some MTs are at the tip while none are present elsewhere in the cell. A full stack extended focus projection was rotated and recorded as a movie using Leica TCS NT software

video2.mov (2 mb)
video2.mov (2.0 MB)

Copyright information

© Springer-Verlag 2003

Authors and Affiliations

  • Ravisha R. Weerasinghe
    • 1
  • David A. Collings
    • 2
  • Eva Johannes
    • 1
  • Nina Strömgren Allen
    • 1
  1. 1.Department of BotanyNorth Carolina State UniversityRaleighUSA
  2. 2.Plant Cell Biology Group, Research School of Biological SciencesAustralian National UniversityCanberra ACT 2601Australia