OPTIMISING TRANSIENT ASSAYS FOR STUDYING THE REGULATION OF PPO GENE EXPRESSION IN PINEAPPLE BLACKHEART

To study factors influencing the development of pineapple blackheart we are undertaking functional analyses of a polyphenol oxidase promoter whose expression is induced in blackheart affected tissues. Since transgenic pineapple fruit take three years to develop, such an analysis must be undertaken using transient assays. In this report we describe experiments aimed at optimising a transient assay system using biolistic DNA delivery in pineapple fruit. Two factors are shown to be critical, namely the use of unmethylated plasmid DNAs prepared using dam- E. coli host strains, and the use of an internal standard to control for the inherent variability of transient expression assays.