Optimization of particle bombardment conditions by ß- glucuronidase (GUS) reporter system in tomato fruit
Fruits of tomato cultivar R-144 (<i>Lycopersicon esculentum</i> Mill. cv. R-144), a variety from Israel, were bombarded on tungsten particles coated with a plasmid containing GusPlus gene that was coded for ß-
glucuronidase (GUS). Peels of target areas of fruits were removed before bombardment, and as such, after 24 h, the effects of different bombardment parameters were evaluated by comparing the numbers
of blue spots which resulted to histological GUS assays. The effects of bombardment pressure, bombardment distance, content of plasmid and bombardment fruit area and fruit maturity stages on GUS expression were investigated. Optimal transient expression of the GusPlus gene was observed after bombardment at 1100 psi, with 0.83 ìg plasmid per shoot, and 6 cm between stop screen and fruit. GUS expression decreased with the process of fruit ripening and increased from fruit shoulder (close to
the end of the stem) to fruit top (blossom end). The highest number of blue spots was 2456.91/ cm2 and was observed in the area of fruit separation zone. As such, the optimized conditions of particle bombardment in this experiment would have significance for its further application in genetic transformation.
Key words: Particle bombardment, ß-glucuronidase (GUS), tomato, fruit, bombardment parameters.