Abstract：S-adenosylmethionine synthetase gene (SAMS) cDNA from a iron-deficiency subtracted library of Malus xiaojinensis was isolated ,which showed 90% identity to the other homolog gene of S-adenolyl-L-methionine synthetase enzyme in GenBank. The full length cDNA of SAMS gene from M. xiaojinensis was obtained using RACE and named as MxSAMS (GenBank accession No.EU639408). The full cDNA of MxSAMS was 1 479 bp with an open reading frame of including a complete ORF of 1 176 bp that encoded a predicted polypeptide of 392 amino acids with the predicted MW of 42.99 kD. MxSAMS showed 88.1%～92.6% amino acids sequence similarity with the other SAMS in plant. The deduced product of MxSAMS had the conserved domain among all the known SAMS, including a ATP binding domain. Southern blot showed that there was only one single copy of MxSAMS gene in the genome. The result of semiquantitative RT-PCR indicated that the MxSAMS in root and leaves of M. xiaojinensis was induced by iron-deficiency stress.
