Abstract: The SAMDC cDNA sequence from jimsonwead (GenBank Accession No: Y07768) was used as electronic probe to hybridize tomato ESTs in GenBank through blastn search. Based on the contig assembled from homologous ESTs, the full-lenghth cDNA of a new member of SAMDC family in tomato was cloned using RT-PCR and RACE，which is 1 847 bp in length with a 523 bp 5′-UTR and a 241 bp 3′-UTR. Corresponding DNA sequence is 3 648 bp, containing three introns in 5′-UTR, and all the cleave sites obey with the GT-AG rule. The gene was designated as SlSAMDC1 (GenBank Accession No: EF550528). SlSAMDC1 consists of three ORFs (tiny uORF, small uORF and main ORF), and the main ORF encodes 360 amino acids with a calculated molecular weight of 39kD. The comparison of deduced amino acid sequence revealed that SlSAMDC1 is highly homologous to other plant SAMDCs, but less similar to human and yeast′s. RT-PCR analysis showed that expression level of SlSAMDC1 was higher in fruit than in any other organs. The upstream regulatory sequence was cloned by genome walking. Further analysis showed that the upstream regulatory sequence contains several Cis-acting elements (eg. W-box, TATA-box, CAAT-box).

Key words: tomato (Solanum lycopersicum), polyamine, S-Adenosylmethionine decarboxylase, gene cloning