Cloning, functional identification and structural modelling of Vitis vinifera S-adenosylmethionine decarboxylase

In this paper we report the cloning and full sequencing of S-adenosylmethionine decarboxylase (SAMDC, EC 4.1.1.50) cDNA from Vitis vinifera L. (VV) leaves, an enzyme belonging to the polyamine biosynthetic pathway, which appears to play an important role in the regulation of plant growth and development. The presence of two overlapping ORFs (tiny ORF and small ORF) upstream of the main ORF is reported in the Vitis cDNA. When the Vitis SAMDC cDNA was expressed in yeast without the two upstream ORFs, the resulting activity was about 50 times higher than the activity obtained with the full cDNA. These results demonstrated the strong regulatory activity of the tiny and small ORFs. RT-PCR expression analysis showed evidence of a similar mRNA level in all the tissues tested, with the exception of the petioles. The VV SAMDC was also modelled using its homologues from Solanum tuberosum and Homo sapiens as template. The present work confirmed, for the first time in a woody plant of worldwide economic interest such as grapevine, the presence of a regulatory mechanism of SAMDC, enzyme that has a well-established importance in the modulation of plant growth and development.