OBJECTIVETo study the acireductone dioxygenase (designated as SmARD) gene of Salvia miltiorrhiza through bioinformatics and characterization of its tissue expression and response expression on stress in shoot.

METHODSmARD gene was obtained by sequencing cDNA library constructed by us. BLAST was used for alignment, ORF finder software was applied to find open reading frame, prosite was used to analyze the protein characterization. Semi-quantitative RT-PCR was used to detect the gene expression level.

RESULTThe full -length cDNA of SmRAD was 688 bp long with a 591 bp ORF (open reading frame) that putatively encoded a polypeptide of 196 amino acids; with a predicted molecular mass of 23.27 kDa. The deduced amino acid sequence of SmRAD of gene shared high homology with other known RADs. Semi-quantitative RT-PCR analysis indicated that SmRAD was constitutively expressed in roots, stems, flower and leaves of S. miltiorrhiza, with the high expression in roots. In addition, SmRAD expression level under different stress condition was also analyzed in root, including signaling components for plant defence responses, such as methyl jasmonate, salicylic acid and ABA, as well as drought, cold and salt abiotic stress. The expression of SmRAD was suppressed by water deficit treatment for 3 d, 150 mmol x L(-1) NaCl, 4 degrees C cold and 100 mmol x L(-1) ABA treatment for 1 d, but induced by 100 mmol x L(-1) MJ and 10 mmol x L(-1) ETH.

CONCLUSIONA novel SmARD gene was cloned from S. miltiorrhiza. This study will enable us to further understand the role of SmARD in the defense response under different abiotic stress and in synthesis of active cmpounds in S. miltiorrhiza at molecular level.