Promotion of gentiopicroside production and transcriptional responses of biosynthetic genes in adventitious root cultures of Gentiana scabra Bunge by elicitation with methyl jasmonate

Abstract

Abiotic elicitors play a crucial role in regulating various aspects of plant growth, development, and specialized metabolism. This study aimed to further increase the gentiopicroside content by screening elicitor types, optimizing elicitation conditions, and estimating transcriptional responses of biosynthetic genes in the adventitious roots of Gentiana scabra. The results showed that methyl jasmonate (MeJA) was the most effective inducer for biomass accumulation in the adventitious roots of G. scabra among tested elicitors, with fresh weight (FW) and dry weight (DW) of 13.26 ± 0.57 g flask⁻¹ and 1.31 ± 0.25 g flask⁻¹, respectively. The effects of the induction time and concentration of MeJA on the biomass and gentiopicroside content in the adventitious roots of G. scabra were investigated. The maximum FW (15.73 ± 0.41 g flask⁻¹) and DW (1.51 ± 0.19 g flask⁻¹) were obtained when the roots were cultured for 6 days in MS liquid medium containing 3.0 mg L⁻¹ 1-naphthlcetic acid (NAA) and 1.0 mg L⁻¹ kinetin (KT) at MeJA concentration of 100 μM L⁻¹. Also, the gentiopicroside content significantly increased to 62.62 ± 0.27 mg g⁻¹ DW, and was 2.49 times higher than that for the nontreated control. The expression levels of 12 candidate gentiopicroside biosynthesis–related genes involved in the mevalonic acid (MVA), methyl erythritol phosphate (MEP), and secoiridoid pathways were estimated in the adventitious roots of G. scabra to further understand the transcriptional response to MeJA elicitation. Among these, 10 genes (ACCT1, HMGR1, MCK1, MVD1, GPPS4, G10H, IS3, DL7H1, DXS5, and ISPH5) were upregulated whereas DXR1 and IDI1 genes were downregulated in the adventitious roots of G. scabra compared with nontreated control, with significant differences having threshold P value ≤0.05. The transcriptional analyses revealed that 12 candidate genes were the key regulated genes in the gentiopicroside biosynthetic pathway. Overall, the findings provided a promising, feasible, and stable approach to utilizing MeJA elicitation to increase the production of valuable gentiopicroside. Additionally, they provided a foundation for future gentiopicroside biosynthesis through metabolic engineering strategies in the adventitious roots of G. scabra.