Cloning and expression analysis of S-adenosylmethionine synthetase gene from Aquilaria sinensis / 药学学报

ABSTRACT

S-adenosylmethionine synthetase, a key enzyme in plant metabolism, plays an essential role in the plant defence system. In present study, a full length cDNA sequence of AsSAMS1 gene was cloned by RACE and reverse transcription PCR from Aquilaria sinensis calli. Meanwhile, the bioinformatics, prokaryotic expression, tissue-specific expression analysis, and expression analysis under different abiotic stresses and hormone treatments were performed. The open reading frame (ORF) of AsSAMS1 gene was 1 183 bp, encoding a protein of 393 amino acids with a calculated molecular mass (MW) of 43.13 kDa. Bioinformatic analysis indicated that AsSAMS1 contained 3 SAMS characteristic sequences. The phylogenetic analysis indicated that AsSAMS1 protein had the highest level of homology with SAMS protein from Glycine soja. The recombinant AsSAMS1 protein was successfully expressed in Escherichia coli BL21 (DE3) cells using the prokaryotic expression vector pET28a-AsSAMS1 and the recombinant AsSAMS1 was purified by Ni2+ affinity chromatography. Expression analysis results in different tissues indicated that AsSAMS1 was primarily observed in stems, and then stem tips and leaves, following by roots. The transcript level of AsSAMS1 and the content of S-adenosylmethionine (SAM) were induced by various abiotic stresses including salt, drought, cold, and heavy metal stress. Furthermore, AsSAMS1 expression level was enhanced upon methyl jasmonate (MeJA), salicylic acid (SA), gibberellin (GA3), and abscisic acid (ABA) treatment. These results provided valuable insights for further study on the role of SAMS in the mechanism of agarwood formation and plant resistance.