Model system for plant cell biology: GFP imaging in living onion epidermalcells

The ability to visualize organelle localization and dynamics is very useful in studying cellular physiological events. Until recently, this has been a ccomplished using a variety of staining methods, However, staining can give inaccurate information due to nonspecific staining, diffusion of the stain or through toxic effects. The ability to target green fluorescent protein (GFP) to various organelles allows for specific labeling of organelles in v ivo. The disadvantages of GFP thus far have been the time and money involve d in developing stable transformants or maintaining cell cultures for trans ient expression. In this paper; we present a rapid transient expression sys tem using onion epidermal peels. We have localized GFP to various cellular compartments (including the cell wall) to illustrate the utility of this me thod and to visualize dynamics of these compartments. The onion epidermis h as large, living, transparent cells in a monolayer making them ideal for vi sualizing GFP. This method is easy and inexpensive, and it allows for testi ng of new GFP fusion proteins in a living tissue to determine deleterious e ffects and the ability to express before stable transformants are attempted .