A. Nebenführ, L. Gallagher, T.G. Dunahay, J.A. Frohlick, A.M. Mazurkiewicz, J.B. Meehl, L.A. Staehelin (1999)
Stop-and-go movements of plant Golgi stacks are mediated by the acto-myosin system
Plant Physiology 121, 1127-1141.
The Golgi apparatus in plant cells consists of a large number of independent Golgi stackTGNGolgi matrix units that appear to be randomly distributed throughout the cytoplasm. To study the dynamic behavior of these Golgi units in living plant cells we have cloned a complementary DNA from soybean, GmMan1, encoding a resident Golgi protein, a-1,2 mannosidase I. The predicted protein of approximately 65 kD shows similarity of general structure and sequence (45 % identity) to animal and fungal Golgi mannosidases. Expression of a GmMan1::GFP fusion construct in tobacco BY-2 suspension culture cells revealed the presence of several hundred to thousands of fluorescent spots. Immuno-electron microscopy demonstrates that these spots correspond to individual Golgi stacks and that the fusion protein is largely confined to the cis-side of the stacks. In living cells, the stacks carry out stop-and-go movements, oscillating rapidly between directed movement and random "wiggling". At any moment about 80 % of the stacks are in a "wiggling" motion while the rest participates to varying degrees in translational movements (maximal velocity 4.2 µm/s). Directed movement is related to cytoplasmic streaming, occurs along straight trajectories, and is dependent upon intact actin microfilaments and myosin motors since treatment with cytochalasin D or butanedione monoxime blocks streaming motion. In contrast, microtubule disrupting drugs appear to have a small but reproducible stimulatory effect on streaming behavior. We present a model which postulates that the stop-and-go motion of Golgi-TGN-units is regulated by "stop signals" produced by ER export sites and locally expanding cell wall domains to optimize ER-to Golgi and Golgi-to cell wall trafficking.
Gene Sequence
The gene sequence of soybean mannosidase can be downloaded from Genbank
under accession number AF126550.
Video Sequences
Since nothing is more convincing than a series of moving pictures I have
posted several short video sequences that illustrate the movement of Golgi
stacks in living BY-2 cells.
Reprint Version
You can download a PDF version of the manuscript from here.