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Title: Interdependence of endomembrane trafficking and actin dynamics during polarized growth of Arabidopsis pollen tubes

item Zhang, Yan
item He, Jummin
item Lee, David
item Mccormick, Sheila

Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/19/2010
Publication Date: 2/24/2010
Publication URL:
Citation: Zhang, Y., He, J., Lee, D., Mccormick, S.M. 2010. Interdependence of endomembrane trafficking and actin dynamics during polarized growth of Arabidopsis pollen tubes. Plant Physiology. 152(4):2200.

Interpretive Summary: Pollen tubes grow from the tip and this growth requires processes called exocytosis and endocytosis, which respectively deliver materials to the growing cell tip and recycle signaling proteins into the cytoplasm. We used various drugs to determine the importance of endocytosis and exocytosis for normal pollen tube growth.

Technical Abstract: During polarized growth of pollen tubes, endomembrane trafficking and actin polymerization are two critical processes that establish membrane/wall homeostasis and maintain growth polarity. Fine-tuned interactions between these two processes are therefore necessary but poorly understood. To better understand such cross talk in the model plant Arabidopsis (Arabidopsis thaliana), we first established optimized concentrations of drugs that interfere with either endomembrane trafficking or the actin cytoskeleton, then examined pollen tube growth using fluorescent protein markers that label transport vesicles, endosomes, or the actin cytoskeleton. Both brefeldin A (BFA) and wortmannin disturbed the motility and structural integrity of ARA7- but not ARA6-labeled endosomes, suggesting heterogeneity of the endosomal populations. Disrupting endomembrane trafficking by BFA or wortmannin perturbed actin polymerization at the apical region but not in the longitudinal actin cables in the shank. The interference of BFA/wortmannin with actin polymerization was progressive rather than rapid, suggesting an indirect effect, possibly due to perturbed endomembrane trafficking of certain membrane-localized signaling proteins. Both the actin depolymerization drug latrunculin B and the actin stabilization drug jasplakinolide rapidly disrupted transport of secretory vesicles, but each drug caused distinct responses on different endosomal populations labeled by ARA6 or ARA7, indicating that a dynamic actin cytoskeleton was critical for some steps in endomembrane trafficking. Our results provide evidence of cross talk between endomembrane trafficking and the actin cytoskeleton in pollen tubes.