Activation of Cryptic Secondary Metabolite Biosynthesis in Tobacco BY-2 Suspension Cells by Epigenetic Modifiers

Cultured plant cells often biosynthesize secondary metabolites to a lesser extent relative to the mother plants. This phenomenon is associated with epigenetic alterations of the biosynthetic gene(s). Here we investigated the effectiveness of epigenetic modifiers, such as inhibitors of histone deacetylase (HDAC) and DNA methyltransferase (DNMT), to activate cryptic secondary metabolite biosynthesis in tobacco (Nicotiana tabacum) BY-2 cells. The BY-2 suspension cells cultured with an HDAC inhibitor, suberoyl bis-hydroxamic acid, exhibited strong biosynthesis of four compounds that were originally present at trace concentrations. The induced compounds were identified as caffeoylputrescine (1), 4-O-β-d-glucopyranosylferulic acid (2), 5-O-caffeoylquinic acid (3), and feruloylputrescine (4). Biosynthetic activation of compounds 1–4 was reproduced by two other HDAC inhibitors. Treatment of the cells with a DNMT inhibitor (zebularine) also activated the biosynthesis of compounds 1–4, but had a limited effectiveness relative to the HDAC inhibitors, indicating that histone acetylation levels are involved more than DNA methylation levels in the epigenetic regulation of the biosynthesis of compounds 1–4 in the BY-2 cells. Following our previous demonstration using cultured cells of a monocotyledonous plant, this study demonstrates the utility of epigenetic modifiers to activate cryptic secondary metabolite biosynthesis in cultured cells of a dicotyledonous plant.