Cloning and expression of an arginine decarboxylase cDNA from Vitis vinifera L. cell-suspension cultures.

Arginine decarboxylase (ADC; EC 4.1.1.19) is a key enzyme in one of the two pathways to putrescine. We present the first ADC cDNA from a woody perennial plant species, the grapevine (Vitis vinifera L.), which exhibits 70-80% homology with other dicot ADCs. The effects of ammonium, nitrate, and putrescine on ADC specific activity, soluble polyamine levels, ADC-mRNA, endogeneous arginine and ornithine, and arginase specific activity were investigated in suspension cultures of grapevine cells. The addition of NH4+ to cells cultured in NH4(+)-free medium, resulted in a 4-fold increase in ADC activity and concomitantly in a 4-fold increase in putrescine and a 3-fold decrease in arginine. During this period ornithine increased and arginase activity followed a reverse pattern of changes compared with ADC. In contrast, the addition of NO3- did not markedly affect ADC activity, putrescine, arginine and ornithine, but transiently increased arginase activity. The addition of putrescine caused a 4-fold decrease in ADC activity and increased arginine, ornithine and arginase activity. The changes in ADC specific activity were not accompanied by analogous changes in the ADC transcript levels. These results further support the view that ADC regulation is not exhibited, at least for the factors considered in this work, at the transcriptional level.