Comparative Transcriptome Analysis Identifies Putative Genes Involved in Dioscin Biosynthesis in Dioscorea...

Area of Science:

• Plant biochemistry
• Metabolic engineering
• Pharmacology

Background:

• Dioscorea zingiberensis rhizome is a traditional Chinese medicine for rheumatic arthritis.
• Dioscin is the primary bioactive compound responsible for its medicinal properties.
• The biosynthetic pathway of dioscin, particularly steps after cholesterol, is largely unknown.

Purpose of the Study:

• To elucidate the biosynthetic pathway of dioscin in Dioscorea zingiberensis.
• To identify key enzymes, including cytochrome P450s (CYPs) and UDP-glycosyltransferases (UGTs), involved in dioscin production.
• To functionally characterize candidate UGT enzymes involved in dioscin biosynthesis.

Main Methods:

• Construction and analysis of a comprehensive D. zingiberensis leaf and rhizome transcriptome.
• Bioinformatic annotation of unigenes against public databases to identify potential biosynthetic enzymes.
• Phylogenetic analysis of candidate CYP and UGT enzymes.
• Cloning and functional characterization of two 3-O-UGT candidates (Dz3GT1 and Dz3GT2).

Main Results:

• A comprehensive transcriptome provided a basis for identifying enzymes in the dioscin pathway.
• 485 unigenes were annotated as CYPs and 195 as UGTs; 165 CYP unigenes correlated with dioscin biosynthesis.
• Four CYP candidates and specific UGTs (3-O-UGTs and rhamnosyltransferases) were identified as potential key players.
• Dz3GT1 and Dz3GT2 demonstrated C3-glucosylation activity on diosgenin, confirming their role in the pathway.

Conclusions:

• This study significantly advances the understanding of the dioscin biosynthesis pathway.
• Identified candidate genes provide a foundation for future research and metabolic engineering efforts.
• The findings facilitate the exploration of genes involved in dioscin biosynthesis for potential applications.