FACTORS AFFECTING GREEN FLUORESCENCE PROTEIN (GFP) GENE EXPRESSION IN OIL PALM AFTER MICROPROJECTILE BOMBARDMENT

Expression of green fluorescence protein (GFP) gene can be visualized under ultraviolet or blue light without any substrate or co-factor addition. It has been used to monitor transient and stable transgene expression in many plant varieties. The effectiveness of gfp gene as a selectable marker for oil palm transformation was evaluated through transient expression of gfp genes in bombarded oil palm embryogenic calli and immature embryos. Different types (version) of gfp genes which are driven by different constitutive promoters were used to transform oil palm target tissues. Some of the gfp genes used were targeted to specific organelle: namely plastid, endoplasmic reticulum and mitochondria. Transient expression of the gfp genes could be detected in oil palm tissues as early as 16 hr after bombardment. It was observed that the number of gfp expressing cells and duration of the gfp gene expression differs from one construct to another. The differences in the gfp constructs performance in oil palm tissues were evaluated based on the following factors: version of the gfp genes, promoter used to drive the gfp gene, backbone vector and the size of the whole plasmid. The CaMV35S promoter was found to be the most effective promoter for driving gfp gene in oil palm tissues followed by HBT and maize ubiquitin promoter. The sGFPS65T was the most effective version of gfp gene for oil palm tissues followed by sGFP and mGFP5. It was also demonstrated that the pUC18 backbone vectors was the most effective vector backbone in expressing the gfp gene in oil palm. Finally, it was observed that the smaller the gfp vector, the higher the number of gfp expressing cells obtained. Possible reasons for these observations were elaborated and discussed.