DEVELOPMENT OF A MICROTARGETING DEVICE FOR PARTICLE BOMBARDMENT OF PLANT MERISTEMS

A gene transfer system for meristem cells was developed on the basis o f a ballistic approach. In order to meet some important prerequisites for an efficient transfer system, such as for example aiming at small tissues and control of penetration of the microprojectiles, we develop ed an acceleration system fundamentally different from the usual macro projectile driven approach. Instead of a macroprojectile, microtargeti ng uses the law of Bernoulli for accleration of highly uniform-sized g old particles. The system is able to deliver 80% of the particles to a n area as small as 150 micron in diameter, which corresponds to the si ze of a meristem. Microtargeting yields gene delivery (measured as num ber of transiently GUS expressing cells to up to 3% of the cells expos ed in the target area or up to 35 x 10(3) cells per cm2. Stable transf ormation of tobacco microcolonies with the microtargeting device was s hown to have an efficiency up to one stable transformant per 1000 cell s exposed to the shot, or up to one transformant per shot. We perform 4 or 5 shots per min. After 30 to 40 shots, reloading can take up to 2 min. Microtargeting is very flexible and allows for the adjustment of the important parameters to fit the requirements of the respective ti ssue.