Optical Trapping

Optical trapping is a technique in which an intensely focused laser beam is used to physically move micron-sized dielectric particles, which might be molecules, organelles or even whole cells. These particles are attracted to the narrowest part of the laser beam which contains a very strong light gradient. Once particles are trapped in this electric gradient, the optical trap (also known as laser tweezers) is controlled via computer software and the particle movement can be observed simultaneously with a confocal laser scanning microscope. In plants optical tweezers have for example been used to micromanipulate the cytoplasm or the nucleus (see Hawes et al. 2010).

We perform our experiments with the commercially available “mmi CellManipulator” in collaboration with Tijs Ketelaar and Norbert de Ruijter at Wageningen University, The Netherlands.

Using this system we have trapped Golgi bodies in arabidopsis and tobacco leaf epidermal cells in wild type and mutant lines. When Golgi bodies are manipulated with the optical trap, the endoplasmic reticulum (ER) remodels quickly and a tubular extension forms, which is following Golgi movement. This shows that in leaves Golgi bodies are firmly tethered to the ER network (Sparkes et al. 2009). On rare occasions we observed Golgi bodies “breaking free”, but they easily reconnected with the ER. We are currently studying the effects of mutations in putative Golgi tethering factors (= golgins) on the connection between Golgi bodies and the ER.

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