Methyl jasmonate influences secondary metabolism and protein expression in Scoparia dulcis

Scoparia dulcis L. (Scrophulariaceae) is a perennial herb distributed in tropical and subtropical regions, and has been used as a folk medicine. This plant was found to produce bicyclic and tetracyclic diterpenes such as scoparic acid A (SA) and scopadulcic acid B (SDB). Our previous studies indicated that SDB production was enhanced by administration of 10µM of methyl jasmonate (MeJA) in leaf organ culture system [1]. Furthermore, calcium signalling was suggested to be involved in the stimulation by MeJA [2].

In order to understand the effect of MeJA on secondary metabolism in S. dulcis, we attempted to analyze proteomes and metabolites in the absence or presence of MeJA. The cultured tissues of S. dulcis were treated with or without 10µM of MeJA and collected after 2 or 4 days of treatment. The extracted proteins were separated by 2D electrophoresis and protein spots were excised from gels. After tryptic digestion, peptides were applied to peptide mass fingerprinting (PMF) analysis. As a result, 21 and 44 spots significantly increased and decreased, respectively, by MeJA treatment. By PMF analyses, it was observed that representative up-regulated spots were identified to be ATPases, whereas down-regulated spots were RuBisCOs. When the tissues were extracted with MeOH, and the extract was analyzed by HPLC and GC-MS after trimethylsilylation, the content of SDB was increased by MeJA treatment, with sterols being decreased. Furthermore, it was observed that production of 6-methoxy-benzoxazolinone (6-MBOA) and its precursor, 4-methoxy-phenylisocyanate, was increased by MeJA.

References: 1. Nkembo, K.M. et al. (2005) Chem. Pharm. Bull. 54: 758–760.

2. Nkembo, K.M. et al. (2005) Plant Biotechnol. 22: 333–337.