Abstract: S-adenosyl-L-methionine decarboxylase (SAMDC) plays an important role in plant abiotic stress resistance. In this study, a 1559 bp full-length SAMDC gene of white clover (Trifolium repens) were cloned by molecular biology technology and named TrSAMDC1. Bioinformatics analysis indicated that TrSAMDC1 has an open reading frame of 1077 bp. The TrSAMDC1 gene encodes an unstable hydrophilic protein of 358 amino acids without transmembrane structure and acting as a signal peptide, which might be located in the cytoplasm. The main components of the secondary structure were a random coil, and the tertiary structure was a homologous dimer. The phylogenetic tree indicates that TrSAMDC1 was closely related to SAMDC of other Leguminosae and highly conserved in evolution. The expression patterns of TrSAMDC1 demonstrates tissue, organ and spatio-temporal specificity under abiotic stress including heavy metal cadmium (CdSO₄), low temperature (4 ℃), high temperature (35 ℃), drought (PEG-6000) and salt (NaCl) and hormone treatments [such as 100 μmol·L^-1 abscisic acid (ABA) and 1 mmol·L^-1 auxin (IAA)]. All treatments could significantly up-regulate the relative expression of leaves TrSAMDC1, and reached the peak after 12 h in most treatments. Although the roots expression of TrSAMDC1 was different from that of control, the sensitivity of roots was significantly lower than that of leaves. The results showed that the TrSAMDC1 could regulated growth and development and responses abiotic stress, especially to high temperature and heavy metal cadmium stress.

Key words: Trifolium repens, gene cloning, SAMDC, abiotic stress, hormone treatment