Characterization of chilli pepper hairy roots expressing the parsley PAL2 cDNA

Transformed hairy root cultures of chilli pepper (Capsicum frutescens cv. cayenne) containing the CaMV 35S promoter linked to the parsley PAL-2 cDNA were generated. These transformants showed increased PAL activity at early and late stages of culture. The morphology, colour and growth rate of these transformants were quite different from the control hairy roots. Measurements of cell dry weight, content of fibre and lignin-like material, suggested that the altered characteristics of the PAL transformants might be linked to lignification. HPLC analyses of phenolic compounds in transgenic roots revealed the accumulation of several substances that were not found in the controls. In response to the addition of salicylic acid or phenylalanine, lignification of the control hairy roots increased. However, the content of lignin-like substances in the PAL transformants was not increased by these treatments. These results indicate that lignification of the PAL transformants had reached a level that could not be further increased.