Imaging the actin cytoskeleton in growing pollen tubes |
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| Authors: | Kathleen L Wilsen Alenka Lovy-Wheeler Boris Voigt Diedrik Menzel Joseph G Kunkel Peter K Hepler |
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| Institution: | (1) Plant Biology Program, University of Massachusetts, 221 Morrill Science Center South, Amherst, MA 01003-9297, USA;(2) Institute of Botany, University of Bonn, Kirschallee 1, Bonn, Germany;(3) Biology Department, University of Massachusetts, 221 Morrill Science Center South, Amherst, MA 01003, USA;(4) Present address: Biological Sciences, University of Northern Colorado, Ross Hall 2480, Greeley, CO 80639, USA |
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| Abstract: | Given the importance of the actin cytoskeleton to pollen tube growth, we have attempted to decipher its structure, organization
and dynamic changes in living, growing pollen tubes of Nicotiana tabacum and Lilium formosanum, using three different GFP-labeled actin-binding domains. Because the intricate structure of the actin cytoskeleton in rapidly
frozen pollen tubes was recently resolved, we now have a clear standard against which to compare the quality of labeling produced
by these GFP-labeled probes. While GFP-talin, GFP-ADF and GFP-fimbrin show various aspects of the actin cytoskeleton structure,
each marker produces a characteristic pattern of labeling, and none reveals the entire spectrum of actin. Whereas GFP-ADF,
and to a lesser extent GFP-talin, label the fringe of actin in the apex, no similar structure is observed with GFP-fimbrin.
Further, GFP-ADF only occasionally labels actin cables in the shank of the pollen tube, whereas GFP-fimbrin labels an abundance
of fine filaments in this region, and GFP-talin bundles actin into a central cable in the core of the pollen tube surrounded
by a few finer elements. High levels of expression of GFP-talin and GFP-fimbrin frequently cause structural rearrangements
of the actin cytoskeleton of pollen tubes, and inhibit tip growth in a dose dependent manner. Most notably, GFP-talin results
in thick cortical hoops of actin, transverse to the axis of growth, and GFP-fimbrin causes actin filaments to aggregate. Aberrations
are seldom seen in pollen tubes expressing GFP-ADF. Although these markers are valuable tools to study the structure of the
actin cytoskeleton of growing pollen tubes, given their ability to cause aberrations and to block pollen tube growth, we urge
caution in their use.
Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.
Financial Source: National Science Foundation grant Nos. MCB-0077599 and MCB-0516852 to PKH EU Research Training Network TIPNET
(project HPRN-CT-2002-00265), Brussels, Belgium, to BV |
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