Rewiring Steroidal Metabolic Pathways for Diosgenin Production in Solanum nigrum

Area of Science:

• Plant Biochemistry
• Metabolic Engineering
• Natural Product Synthesis

Background:

• Diosgenin is a vital precursor for synthesizing steroidal drugs like corticosteroids and sex hormones.
• Current commercial production relies on Dioscorea spp. tubers, necessitating alternative sources for enhanced production.
• Solanum nigrum accumulates steroidal compounds, suggesting its potential as a diosgenin production platform.

Purpose of the Study:

• To investigate Solanum nigrum as a novel host for diosgenin production.
• To elucidate the metabolic pathways involved in steroidal glycoalkaloid (SGA) and steroidal saponin (STS) biosynthesis in S. nigrum.
• To engineer S. nigrum for increased diosgenin yield.

Main Methods:

• Characterization of SGA and STS biosynthesis pathways in S. nigrum, focusing on CYP450 (SnGAME4) and 3β-hydroxysteroid dehydrogenase/isomerase (SnGAME25) enzymes.
• Genetic disruption of SnGAME4 and SnGAME25 to alter metabolic flux.
• Identification of endogenous glucosidases and application of spontaneous fermentation to convert furostanol to spirostanol structures.
• Engineering S. nigrum for increased fruit number and combining with SnGAME4 mutation.

Main Results:

• Solanum nigrum naturally accumulates SGAs (spirostanol type) in green fruits and STSs (furostanol type) in leaves.
• Disruption of SnGAME4 and SnGAME25 shifted metabolism towards furostanol-type glycosides, yielding low diosgenin upon hydrolysis.
• Conversion of furostanol to spirostanol structures via fermentation and enzymatic activity increased diosgenin yield.
• Solanum nigrum green fruits achieved up to 1% diosgenin of dry weight.
• Engineered S. nigrum with increased fruit number and SnGAME4 mutation showed enhanced diosgenin production potential.

Conclusions:

• Solanum nigrum is a promising and scalable alternative host for diosgenin production.
• Metabolic engineering and fermentation strategies can optimize diosgenin yield from S. nigrum.
• This study establishes a foundation for utilizing S. nigrum in the industrial synthesis of steroid precursors.