Journal Article

Vesicle trafficking dynamics and visualization of zones of exocytosis and endocytosis in tobacco pollen tubes

Laura Zonia and Teun Munnik

in Journal of Experimental Botany

Published on behalf of Society for Experimental Biology

Volume 59, issue 4, pages 861-873
Published in print March 2008 | ISSN: 0022-0957
Published online February 2008 | e-ISSN: 1460-2431 | DOI: https://dx.doi.org/10.1093/jxb/ern007

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Pollen tubes are one of the fastest growing eukaryotic cells. Rapid anisotropic growth is supported by highly active exocytosis and endocytosis at the plasma membrane, but the subcellular localization of these sites is unknown. To understand molecular processes involved in pollen tube growth, it is crucial to identify the sites of vesicle localization and trafficking. This report presents novel strategies to identify exocytic and endocytic vesicles and to visualize vesicle trafficking dynamics, using pulse-chase labelling with styryl FM dyes and refraction-free high-resolution time-lapse differential interference contrast microscopy. These experiments reveal that the apex is the site of endocytosis and membrane retrieval, while exocytosis occurs in the zone adjacent to the apical dome. Larger vesicles are internalized along the distal pollen tube. Discretely sized vesicles that differentially incorporate FM dyes accumulate in the apical, subapical, and distal regions. Previous work established that pollen tube growth is strongly correlated with hydrodynamic flux and cell volume status. In this report, it is shown that hydrodynamic flux can selectively increase exocytosis or endocytosis. Hypotonic treatment and cell swelling stimulated exocytosis and attenuated endocytosis, while hypertonic treatment and cell shrinking stimulated endocytosis and inhibited exocytosis. Manipulation of pollen tube apical volume and membrane remodelling enabled fine-mapping of plasma membrane dynamics and defined the boundary of the growth zone, which results from the orchestrated action of endocytosis at the apex and along the distal tube and exocytosis in the subapical region. This report provides crucial spatial and temporal details of vesicle trafficking and anisotropic growth.

Keywords: Endocytosis; exocytosis; hydrodynamics; lipophilic FM dyes; pollen tube growth; vesicle trafficking

Journal Article.  8052 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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