Sodium nitroprusside enhances the elicitation power of methyl jasmonate for ginsenoside production in Panax ginseng roots

The effects of methyl jasmonate (MJ) and sodium nitroprusside (SNP) on ginsenoside production were investigated in ginseng adventitious roots. The role of nitric oxide (NO) production and reactive oxygen species (ROS) was also elucidated. Different concentrations of SNP were applied to ginseng adventitious roots. The highest accumulation of ginsenoside was recorded for 200 mu M of SNP. Ginsenoside biosynthesis-related genes were highly induced by 100 mu M MJ in combination with 200 mu M of SNP compared to MJ alone , which subsequently led to higher ginsenoside accumulation after 72 h. For the first time, a full length NO-associated (NOA) cDNA clone was isolated and characterized from the embryogenic callus of ginseng with predicted localization in the mitochondria. The open reading frame was 1626 bp with a deduced amino acid sequence of 541 residues, which shared a high degree of homology with the NO associated protein from Solanum tuberosum. PgNOA showed higher transcript levels in treated roots with combined MJ and SNP compared to MJ alone. Increased production of NO was observed after addition of SNP to MJ-treated samples. There was no difference in transcript levels for lipoxygenase, a key enzyme in the jasmonic acid pathway in MJ- and SNP-treated roots compared to roots treated with MJ alone. The superoxide dismutase 1 (SOD1) gene was highly responsive to MJ and SNP treatment compared to treatment with MJ alone. SOD1 catalyzes the dismutation of toxic superoxide radicals into either molecular oxygen or hydrogen peroxide (H2O2) resulting in higher production of these products. H2O2 can be subsequently converted to water by the action of ascorbate peroxidase (APX), which was highly expressed in combined treatment with MJ and SNP compared to treatment with MJ alone. The results obtained here suggest that SNP enhanced the elicitation power of MJ for increased ginsenoside accumulation. Moreover, this process was mediated by a complex signal transduction network including NO biosynthesis and ROS generation.