PgHMGR2-modulated saponin accumulation in P. grandiflorus. (A) Hairy root generation through overexpression of PgHMGR2 in P. grandiflorus. (B) RT-PCR validation of transgenic hairy root. (C) Hairy root generation via RNA interference of PgHMGR2 in P. grandiflorus. (D) Relative expression of genes involved in saponin biosynthesis in PgHMGR2 overexpression lines. PgHMGR2-OE1, PgHMGR2-OE2, and PgHMGR2-OE3 are three independent PgbHLH28 overexpression lines. (E) Relative expression of genes involved in saponin biosynthesis pathway in PgHMGR2 silencing lines. PgHMGR2-RNAi1, PgHMGR2-RNAi2, and PgHMGR2-RNAi3 are three independent PgHMGR2 silencing lines. (F) Total saponin, oleanolic acid, and β-amyrin content in overexpression and RNA silencing lines.