Effects of methyl jasmonate with indole-3-acetic acid and 6-benzylaminopurine on the secondary metabolism of cultured Onosma paniculatum cells

Methyl jasmonate (MeJA) interacted significantly with both indole-3-acetic acid (IAA) and 6-benzylaminopurine (BA) to influence cell growth of cultured Onosma paniculatum cells. Cell growth decreased with increasing concentrations of MeJA from 0.004-4.45 muM with or without IAA and BA. The same concentrations of MeJA (0-4.45 muM) increased the cell growth with IAA and BA, when administered to the cultured cells in M-9 medium. This was found to enhance the production of shikonin. The optimum time for MeJA addition for enhanced shikonin formation was 4 d after cell inoculation in M-9 medium. Furthermore, shikonin formation was affected significantly by both MeJA/IAA and MeJA/BA combinations. Shikonin content was enhanced by increasing MeJA concentrations with IAA concentrations in the range of 0-28 muM and with BA concentrations in the range of 0-44.38 muM in MeJA/IAA and MeJA/BA experiments, respectively. The optimal combination of MeJA and IAA was 4.45 muM and 0.28 muM, while MeJA and BA concentrations of 4.45 muM and 2.22 muM were optimal for shikonin formation. The result also showed that MeJA increased phenylalanine ammonia-lyase (PAL) and p-hydroxybenzoic acid-geranyltransferase (PHB-geranyltransferase) activities during the course of shikonin formation, but decreased the activity of PHB-O-glucosyltransferase within 9 d after inoculation. These results suggest that enhanced shikonin formation in cultured Onosma paniculatum cells induced by MeJA involves regulation of the key enzyme activities.