Improving diosgenin production and its biosynthesis in Trigonella foenum-graecum L. hairy root cultures

•Different strains of Agrobacterium rhizogenes were used to induction of hairy roots in two low- and high-diosgenin producing fenugreek genotypes.•The expression rate of the biosynthetic genes and diosgenin content were measured.•Induction of hairy roots considerably increased the production of diosgenin as compared with the plant itself.•By converting dioscin to diosgenin, the non-specific beta-glucosidase activity of bacterial genes leads to higher accumulation of diosgenin in hairy roots.•Key genes involved in plastid 2-C-methyl-D-erythritol 4-phosphate pathway are highly expressed in the induced hairy roots. Induction of hairy roots stemmed from Agrobacterium rhizogenes transformation, is a key step to reach mass production of secondary metabolites in medicinal plants. Accordingly, this study is aimed to investigate potential impact of different A. rhizogenes strains, including ATCC15834, R1000, A4 and C58, on diosgenin biosynthesis in high- “Boshruyeh” (23.8 mg/gDW) and low “Hamadan” (6.4 mg/gDW) diosgenin-producing genotypes of fenugreek. Interestingly, comparing the metabolite extracted from both leaves and hairy roots of these genotypes suggested that hairy roots are promising platform to produce scalable amount of diosgenin, producing 143.96 mg/gDW in high diosgenin producing hairy roots (A4-mediated hairy roots induction in “Boshruyeh” (BA4)), while 23.8 mg/gDW in high diosgenin producing genotype. Transcript abundance of 10 genes involved in diosgenin biosynthesis pathway as well as three rate-limiting genes; i.e 1-deoxy-D-xylulose-5-phosphate synthase (DXS), 1-deoxy-D-xylulose 5-phosphate reductoisomerase (DXR) and 4-hydroxy-3-methylbut-2-enyl diphosphate reductase, functioning in plastid 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway were measured. Comparison of the transcription and metabolite analysis revealed that the more expression of Δ24-reductase gene, the higher accumulation of diosgenin in the hairy roots. In high diosge nin producing hairy roots, the expression of Δ24-reductase gene were significantly up-regulated (8-folds). Moreover, integration of metabolite and transcript results revealed that A4 has a strong capacity in boosting diosgenin accumulation in the both genotypes. These results may lead to the next step in production of diosgenin in scalable and commercial levels.