Plant Cell Hybrigenics The Protein Interactions Experts
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

First published online August 25, 2009; 10.1105/tpc.109.210812

The Plant Cell 21:2193

This Article
Right arrow Full Text (PDF)
Right arrow PPT slides of all figures
Right arrow All Versions of this Article:
21/8/2193    most recent
tpc.109.210812v1
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Related articles in Plant Cell
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via CrossRef
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Farquharson, K. L.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Farquharson, K. L.
Agricola
Right arrow Articles by Farquharson, K. L.

IN BRIEF

On the Origin of Cortical Microtubules

Kathleen L. Farquharson

Science Editor

kfarquharson{at}aspb.org

Epidermal hypocotyl cells are characterized by a highly structured cortical microtubule array, consisting of bundles of polarized, parallel microtubules that gradually migrate across the cortex in a rotary fashion (Chan et al., 2007Go). In animal cells, microtubules arise from centrosomes; however, plant cells lack centrosomes, and microtubules are thought to self-organize into structured arrays (reviewed in Dixit and Cyr, 2004Go). In a study using green fluorescent protein (GFP)-tubulin, Murata et al. (2005)Go demonstrated that new microtubules branch off preexisting microtubules in the cortex of plant cells. However, this capacity for branching seems at odds with the tendency of microtubules to form parallel bundles.

Chan et al. (pages 2298–2306) hypothesized that cortical microtubule arrays persist because some of the newly formed microtubules grow along the preexisting microtubules on which they form. To test this hypothesis, they analyzed the origin of microtubules in the cortex of Arabidopsis interphase hypocotyl cells using fluorescently tagged Arabidopsis End binding 1 protein (Pro35S:AtEB1a-GFP). In contrast with GFP-tubulin, which labels entire microtubules and does not readily distinguish between neighboring microtubules, AtEB1a-GFP predominantly labels the fast-growing plus ends of microtubules and thereby allows individual microtubules, of known polarity, to be tracked. Apart from labeling the plus end comets of emerging microtubules, AtEB1a-GFP also labeled the positions on the mother microtubules from which new microtubules arose. To confirm that the EB1a foci on mother microtubules indeed represent microtubule-nucleating sites, the researchers transiently coexpressed in Nicotiana benthamiana Pro35S:AtEB1a-GFP and RFP-NEDD1, which labels the centrosome in animal cells (Fant et al., 2009Go) and the spindle poles in plant mitotic cells (Zeng et al., 2009Go). Since new microtubules were found to emerge from foci labeled with both of these probes, EB1 was considered to be a faithful marker of microtubule nucleation.

The authors generated kymographs, which track the origin and fate of fluorescently labeled microtubules, from sets of time-lapse confocal images. Most new microtubules were found to branch forward, toward the plus end of the mother microtubule, and branching occurred on both sides of the mother microtubule. However, in support of the researchers' hypothesis, 38% (n = 165) of new microtubules grew along the axis of the mother microtubule (see figure ). Few emerging microtubules grew backward, toward the minus end of the mother microtubule. Furthermore, new microtubules frequently arose from points where two microtubules crossed, and most of these microtubules followed the axis of one of the preexisting microtubules. These results were confirmed in seedlings expressing ProAtSPR1:GFP-AtSPR1, another marker of microtubule plus ends in plants.


Figure 1
View larger version (137K):
[in this window]
[in a new window]
[as a PowerPoint slide]
  		Kymograph showing a single microtubule (+1) emerging from a stationary focus on the mother microtubule (F; vertical line) and growing along the mother microtubule (0° axis). Bar = 4 µm in the x axis and 98 s in the y axis.

 
Thus, cortical microtubules were found to persist because a population of new microtubules grows along the tracks of existing microtubules.

Footnotes

www.plantcell.org/cgi/doi/10.1105/tpc.109.210812

REFERENCES

Chan, J., Calder, G.M., Fox, S., and Lloyd, C.W. (2007). The cortical microtubule array undergoes rotary movements in Arabidopsis hypocotyl epidermal cells. Nat. Cell Biol. 9: 171–175.[CrossRef][Web of Science][Medline]

Chan, J., Sambade, A., Calder, G., and Lloyd, C. (2009). Arabidopsis cortical microtubules are initiated along, as well as branching from, existing microtubules. Plant Cell 21: 2298–2306.[Abstract/Free Full Text]

Dixit, R., and Cyr, R. (2004). The cortical microtubule array: from dynamics to organization. Plant Cell 16: 2546–2552.[Free Full Text]

Fant, X., Gnadt, N., Haren, L., and Merdes, A. (2009). Stability of the small gamma-tubulin complex requires HCA66, a protein of the centrosome and the nucleolus. J. Cell Sci. 122: 1134–1144.[Abstract/Free Full Text]

Murata, T., Sonobe, S., Baskin, T.I., Hyodo, S., Hasezawa, S., Nagata, T., Horio, T., and Hasebe, M. (2005). Microtubule-dependent microtubule nucleation based on recruitment of gamma-tubulin in higher plants. Nat. Cell Biol. 7: 961–968.[CrossRef][Web of Science][Medline]

Zeng, C.J., Lee, Y.R., and Liu, B. (2009). The WD40 repeat protein NEDD1 functions in microtubule organization during cell division in Arabidopsis thaliana. Plant Cell 21: 1129–1140.[Abstract/Free Full Text]


Related articles in Plant Cell:

Arabidopsis Cortical Microtubules Are Initiated along, as Well as Branching from, Existing Microtubules
Jordi Chan, Adrian Sambade, Grant Calder, and Clive Lloyd
Plant Cell 2009 21: 2298-2306. [Abstract] [Full Text]  




This Article
Right arrow Full Text (PDF)
Right arrow PPT slides of all figures
Right arrow All Versions of this Article:
21/8/2193    most recent
tpc.109.210812v1
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Related articles in Plant Cell
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via CrossRef
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Farquharson, K. L.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Farquharson, K. L.
Agricola
Right arrow Articles by Farquharson, K. L.

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
ASPB Publications THE PLANT CELL PLANT PHYSIOLOGY
Copyright © 2009 by the American Society of Plant Biologists