Molecular cloning of sugarcane S-adenosylmethionine decarboxylase gene (Sc-SAMDC) and its expression analysis.

【Objective】 In this study, the obtainment and sequence analysis of the S-adenosylmethionine decarboxylase (SAMDC) gene from sugarcane (Saccharum officinarum) was conducted, and then its expression in prokaryotic system and its expression profiles under different stress treatments were also carried out. 【Method】 Firstly, through extensive sequencing and bioinformatics analysis, the full-length cDNA of sugarcane SAMDC gene, named as Sc-SAMDC, was obtained from sugarcane stem cDNA library, and its sequence characters were also analyzed. Secondly, the fused expression plasmid was constructed by inserting the cDNA fragment encoding the mature peptide of SAMDC into prokaryotic expression vector pET29a(+), and the positive recombinant was transformed into Esherichia coli BL21(DE3). Finally, the expression profiles of Sc-SAMDC in sugarcane seedling under different stresses were analyzed by Real-time qPCR. 【Result】 Sequence analysis showed that the full-length cDNA sequence of Sc-SAMDC (GenBank Accession number: GQ246459) was 1 968 bp, with three open reading frames (ORFs), tiny ORF (tORF), upstream ORF (uORF) and main ORF(mORF). The mORF was 1 200 bp encoding 399 amino acid residues with a molecular mass of 43.6 kD, and the deduced protein had two highly conserved function domains (proenzyme cleavage site and PEST domain). The SDS-PAGE showed that the expression protein is a fusion protein and the molecular weight is about 50 kD. The result of Real time qPCR analysis showed that Sc-SAMDC responded differently to various exogenous treatments, induced by both PEG and NaCl, butinhibited by SA and H2O2. 【Conclusion】 A SAMDC gene from sugarcane was successfully cloned and expressed in E. coli, the sequence characters and the expression profiles of this gene under different stresses were also analyzed.