Changes in Amines and Biosynthetic Enzyme Activities in p-Fluorophenylalanine Resistant and Wild Type Tobacco Cell...

The levels of free amines and the activities of their biosynthetic enzymes were measured in a p-fluorophenylalanine resistant Nicotiana tabacum L. cv Xanthi cell line (TX4) which accumulates high levels of cinnamoylamides, and a wild type cell line (TX1). Putrescine in TX1 and spermidine in TX1 and TX4 increased 4-fold by day 4 but declined by day 8 of the culture period. Spermine levels were consistently low, while tyramine was not found in TX1 until day 9 when a gradual rise was noted. Ornithine decarboxylase activity in TX1 and TX4 increased slightly through day 2 but declined gradually thereafter. S-Adenosylmethionine decarboxylase activity remained low throughout the culture period, and tyrosine and arginine decarboxylases in TX1 were very low in activity. In contrast, the activities of tyrosine and arginine decarboxylases were elevated in TX4, but a 3-fold increase in tyramine after a subculture was not accompanied by a rise in tyrosine decarboxylase. However, tyrosine decarboxylase activity did increase during a second rise in tyramine levels in aging cells, late in the culture period. Although significant differences exist in amine levels, between TX4 and TX1, it is unclear how altered amine metabolism relates to p-fluorophenylalanine resistance.