Correlation between Phenylalanine Ammonia Lyase Activity and Phenolic Biosynthesis in p-Fluorophenylalanine-sensitive and -resistant Tobacco and Carrot Tissue Cultures

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Abstract
Phenylalanine ammonia lyase (PAL) activity was measured in p-fluorophenylalanine (PFP)-sensitive and -resistant tobacco (Nicotiana tabacum L.) and carrot (Daucus carota L.) cell lines which are known to oversynthesize phenylalanine. A correlation between phenolic levels and PAL activities was detected. The phenylalanine analog-resistant and -sensitive carrot cells showed no differences in the accumulation of phenolic compounds and PAL activities. The PFP-resistant tobacco cells, however, had 10 times higher levels of phenolics and also 10 to 20 times higher PAL activities than the PFP-sensitive line. The PAL activity in the resistant tobacco line increased dramatically after inoculation of the cells into fresh medium. Conditions affecting this increase were characterized.