GENETIC-ENGINEERING OF PHENOLIC METABOLIS M IN POPLAR IN RELATION WITH RESISTANCE AGAINST PATHOGENS

Flavonoids being involved in various defence mechanisms, attempts to i mprove resistance against pathogens have been developed in poplar (Pop ulus tremula x P. alba) in order to increase flavonoid content through genetic engineering. The Petunia chs A gene driven by the CaMV 35S pr omoter with a double enhancer and the gus and npt II marker genes were constructed and used in cocultivation with excised poplar internodes. Several transgenic lines were created and analysed by northern blotti ng. Their developmental patterns were examined and flavonoids were loc alized in situ using various reagents. Only one transgenic line provid ed with a strong chs overexpression was characterized by flavonoids lo cated in both cortical and peripheral tissues of the stem. Differences between controls and the other transgenic lines were quantitative and flavonoids were mainly found in superficial tissues (epidermis, subep idermis and suber) as if only these tissues were provided with adequat e enzymes or substrates for the full biosynthetic pathway leading to f lavonoids.