Journal Article

Microtubule- and Actin Filament-Dependent Motors are Distributed on Pollen Tube Mitochondria and Contribute Differently to Their Movement

Silvia Romagnoli, Giampiero Cai, Claudia Faleri, Etsuo Yokota, Teruo Shimmen and Mauro Cresti

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 48, issue 2, pages 345-361
Published in print February 2007 | ISSN: 0032-0781
Published online February 2007 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcm001
Microtubule- and Actin Filament-Dependent Motors are Distributed on Pollen Tube Mitochondria and Contribute Differently to Their Movement

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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The pollen tube exhibits cytoplasmic streaming of organelles, which is dependent on the actin–myosin system. Although microtubule-based motors have also been identified in the pollen tube, many uncertainties exist regarding their role in organelle transport. As part of our attempt to understand the role of microtubule-based movement in the pollen tube of tobacco, we investigated the cooperation between microtubules and actin filaments in the transport of mitochondria and Golgi vesicles, which are distributed differently in the growing pollen tube. The analysis was performed using in vitro motility assays in which organelles move along both microtubules and actin filaments. The results indicated that the movement of mitochondria and Golgi vesicles is slow and continuous along microtubules but fast and irregular along actin filaments. In addition, the presence of microtubules in the motility assays forces organelles to use lower velocities. Actin- and tubulin-binding tests, immunoblotting and immunogold labeling indicated that different organelles bind to identical myosins but associate with specific kinesins. We found that a 90 kDa kinesin (previously known as 90 kDa ATP-MAP) is associated with mitochondria but not with Golgi vesicles, whereas a 170 kDa myosin is distributed on mitochondria and other organelle classes. In vitro and in vivo motility assays indicate that microtubules and kinesins decrease the speed of mitochondria, thus contributing to their positioning in the pollen tube.

Keywords: Kinesin; Microtubule; Mitochondria; Myosin; Organelle movement; Pollen tube

Journal Article.  9799 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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