The "stop-and-go" movement of Golgi stacks: illuminating the dynamic association between membranes and cytoskeleton

The manuscript by Nebenführ and coworkers showed that the plant Golgi bodies move along actin filaments and that transport occurs in a way called as "stop-and-go". This means that Golgi bodies can move along actin filaments but they can also temporarily stop at precise locations in the plant cell. Constant transport guarantees that Golgi bodies are uniformly distributed in the cell, while the stop phase is required for production of vesicles at specific sites. Using techniques of protein engineering (cloning the GmMan1 gene, which encodes the resident Golgi protein á-1,2 mannosidase I, and fusing it with GFP) the authors labeled specifically the Golgi bodies and were able to visualize the movement of Golgi stacks in living BY-2 cells. The Golgi stacks performed a "stop-and-go" movement, in which directed movement is dependent on cytoplasmic streaming occurring along actin microfilaments. Authors also observed that microtubule-disrupting drugs had a stimulatory effect on organelle streaming. Nebenführ and coworkers suggested a model in which the "stop-and-go" movement of Golgi units along actin filaments is regulated by stop messages produced by the endoplasmic reticulum. The stop signals are used to optimize the interaction between Golgi and ER in order to regulate the trafficking of proteins from membrane compartments to the cell wall. Observation of moving Golgi bodies in the plant cell revealed a phenomenon that was already been predicted previously but never described before. I would like to support this article for the special issue of Plant Physiology dedicated to the celebration of the 25,000th published Article. As I work in related fields, I found the manuscript of Nebenführ and coworkers fascinating and highly motivating. The possibility to observe Golgi bodies while moving along actin filaments in living cells opened enormous prospective of research and provided critical information on the dynamic interactions between plant cell organelles and the cytoskeleton, a process that also controls critical aspects of the plant cell (such as shape and growth direction). Following this manuscript, other papers have shown the movement of different organelle classes (such as endosomes and secretory vesicles) in living plant cells. Transport of proteins from ER to Golgi and then to the cell wall matrix is an important process because it is used by plant cells to regulate the secretion of enzymes that construct the cell wall polysaccharides thus determining the shape and growth direction of the cell. Understanding the molecular mechanism of this process is fundamental for realizing how a plant cell coordinates the cytoskeletal activity with membrane trafficking and cell wall construction.