Do Phytotropins Inhibit Auxin Efflux by Impairing Vesicle Traffic?

Jan Petrášek, Adriana Černá,  Kateřina Schwarzerová,  Miroslav Elčkner,  David A. Morris, and Eva Zažímalová

Institute of Experimental Botany, The Academy of Sciences of the Czech Republic, Rozvojová 135, CZ-16502 Prague 6, Czech Republic (J.P., M.E., D.A.M., E.Z.); and Department of Plant Physiology, Faculty of Science, Charles University, Viničná, CZ-12844 Prague 2, Czech Republic (J.P., A.Č., K.S.)

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The effect of 20 brefeldin A (BFA) and 1-N-naphthylphthalamic acid (NPA) on the arrangement of endoplasmic reticulum (ER) in 2-day old BY-2 cells expressing mGFP5-ER.

1) Control cells incubated 30 min in medium containing appropriate volume of a solvent (ethanol).

In exponentially growing control interphase cells, ER was present in the form of a tubular network penetrating not only the cortical layer of cytoplasm, but also the transvacuolar strands and perinuclear region. Within this network, small motile bodies were observed. The movement of these bodies was observed over the surface of the network of ER tubules that constantly changed its orientation and pattern.

2) The effect of 30-min incubation in 20 μM BFA.

Treatment of cells with 20 μM BFA for 30 min resulted in disintegration of the fine tubular network of ER, the formation of large sheets of ER, and the aggregation of the signal into a large number of bright fluorescence spots (Fig. 5b). However, the first observable effects of BFA were clear after only 5 min (data not shown), when disintegration of the tubular network and formation of fluorescent spots started. On the other hand, even after 30 min of 20 μM BFA treatment there were still cells with no obvious damage of ER. The accumulation of GFP fluorescence was also observed in the perinuclear region.

a) Optical section through a cortical cytoplasm.

b) Optical section through the center of a cell.