Methyl Jasmonate Activates the 2C Methyl-D-erithrytol 2,4-cyclodiphosphate Synthase Gene and Stimulates Tanshinone Accumulation in Salvia miltiorrhiza Solid Callus Cultures

The present study characterizes the 5′ regulatory region of the SmMEC gene. The isolated fragment is 1559 bp long and consists of a promoter, 5′UTR and 31 nucleotide 5′ fragments of the CDS region. In silico bioinformatic analysis found that the promoter region contains repetitions of many potential cis-active elements. Cis-active elements associated with the response to methyl jasmonate (MeJa) were identified in the SmMEC gene promoter. Co-expression studies combined with earlier transcriptomic research suggest the significant role of MeJa in SmMEC gene regulation. These findings were in line with the results of the RT-PCR test showing SmMEC gene expression induction after 72 h of MeJa treatment. Biphasic total tanshinone accumulation was observed following treatment of S. miltiorrhiza solid callus cultures with 50–500 μM methyl jasmonate, with peaks observed after 10–20 and 50–60 days. An early peak of total tanshinone concentration (0.08%) occurred after 20 days of 100 μM MeJa induction, and a second, much lower one, was observed after 50 days of 50 μM MeJa stimulation (0.04%). The dominant tanshinones were cryptotanshinone (CT) and dihydrotanshinone (DHT). To better understand the inducing effect of MeJa treatment on tanshinone biosynthesis, a search was performed for methyl jasmonate-responsive cis-active motifs in the available sequences of gene proximal promoters associated with terpenoid precursor biosynthesis. The results indicate that MeJa has the potential to induce a significant proportion of the presented genes, which is in line with available transcriptomic and RT-PCR data.