Optimization of physical and biological parameters for transient expression of uidA gene in embryogenic callus of date palm (Phoenix dactylifera L.) via particle bombardment

Abstract

The objective of this study was to establish an efficient genetic transformation system in date palm (

Phoenix dactylifera L.) using particle bombardment. Somatic tissues derived from offshoots' meristem cultures were bombarded with genetic constructs harboring the uidA gene under control of the CaMV 35S or Act1 promoter. The effects of different physical, biological and DNA parameters were evaluated by comparing the number of blue spots obtained from the histochemical GUS assay. Optimal transient expression of the uidA gene in embryogenic calli was observed using the following conditions: bombardment at 1100 psi, 9 cm target distance, a 1.6 μm gold particle size coated with 2.5 μg of DNA, 26 inHg vacuum pressure, 3 mm distance between the rupture disk and macrocarrier and osmotic pretreatment of 0.4 M mannitol followed by 60 min of air desiccation. Significantly, higher expression rates were observed when the construct carrying the Act1 promoter was employed. The highest number of blue spots obtained in this protocol was 1500 blue spots per 1 cm2 of bombarded tissue. Achievement of these optimized conditions considered as the first report of its kind is expected to provide valuable information for the generation of transgenic date palm plants.