CHARACTERIZATION OF THE S-ADENOSYLMETHIONINE DECARBOXYLASE (SAMDC) GENE OF POTATO

S-adenosylmethionine decarboxylase (SAMDC) is involved in the biosynth esis of the polyamines, spermidine and spermine. Recently, we reported the isolation of a putative cDNA clone of the SAMDC clone of potato ( Plant Mol Biol 20; 641-651). In order to confirm that the potato genes does encode SAMDC, a complementation experiment with a yeast strain t hat possesses a null mutation in the SAMDC gene was performed. The yea st strain contains a deletion-insertion mutation in the SAMDC gene and has an absolute requirement for the addition of exogenous spermidine for growth. When the full-length potato cDNA was expressed in the muta nt yeast strain there was no longer a requirement for exogenous spermi dine. Immunoblotting experiments suggest that the potato SAMDC gene pr oduct has an apparent molecular mass of 39 kDa. Expression of the SAMD C gene was high in the young and actively dividing tissues and low in the mature and non-dividing tissues of both vegetative and reproductiv e organs. Additionally, isolation and characterisation of the correspo nding genomic clone is reported. The gene has one intron in its 5'-unt ranslated sequence but otherwise the transcribed portion is identical to the cDNA clone.