METABOLISM OF POLYAMINES IN TRANSGENIC CELLS OF CARROT EXPRESSING A MOUSE ORNITHINE DECARBOXYLASE CDNA

The metabolisms of arginine (Arg), ornithine (Orn), and putrescine wer e compared in a nontransgenic and a transgenic cell line of carrot (Da ucus carota L.) expressing a mouse Orn decarboxylase cDNA. [C-14]Arg, [C-14]Orn, and [C-14]putrescine were fed to cells and their rates of d ecarboxylation, uptake, metabolism into polyamines, and incorporation into acid-insoluble material were determined. Transgenic cells showed higher decarboxylation rates for labeled Orn than the nontransgenic ce lls. This was correlated positively with higher amounts of labeled put rescine production from labeled Orn. With labeled Arg, both the transg enic and the nontransgenic cells exhibited similar rates of decarboxyl ation and conversion into labeled putrescine. When [C-14]putrescine wa s fed, higher rates of degradation were observed in transgenic cells a s compared with the nontransgenic cells. It is concluded that (a) incr eased production of putrescine via the Orn decarboxylase pathway has n o compensatory effects on the Arg decarboxylase pathway, and (b) highe r rates of putrescine production in the transgenic cells are accompani ed by higher rates of putrescine conversion into spermidine and spermi ne as well as the catabolism of putrescine.