Genome-Wide Identification of CYP72A Gene Family and Expression Patterns Related to Jasmonic Acid Treatment and Steroidal Saponin Accumulation in Dioscorea zingiberensis

Abstract

Dioscorea zingiberensis is a medicinal herb containing a large amount of steroidal saponins, which are the major bioactive compounds and the primary storage form of diosgenin. The CYP72A gene family, belonging to cytochromes P450, exerts indispensable effects on the biosynthesis of numerous bioactive compounds. In this work, a total of 25 CYP72A genes were identified in D. zingiberensis and categorized into two groups according to the homology of protein sequences. The characteristics of their phylogenetic relationship, intron–exon organization, conserved motifs and cis-regulatory elements were performed by bioinformatics methods. The transcriptome data demonstrated that expression patterns of DzCYP72As varied by tissues. Moreover, qRT-PCR results displayed diverse expression profiles of DzCYP72As under different concentrations of jasmonic acid (JA). Likewise, eight metabolites in the biosynthesis pathway of steroidal saponins (four phytosterols, diosgenin, parvifloside, protodeltonin and dioscin) exhibited different contents under different concentrations of JA, and the content of total steroidal saponin was largest at the dose of 100 μmol/L of JA. The redundant analysis showed that 12 DzCYP72As had a strong correlation with specialized metabolites. Those genes were negatively correlated with stigmasterol and cholesterol but positively correlated with six other specialized metabolites. Among all DzCYP72As evaluated, DzCYP72A6, DzCYP72A16 and DzCYP72A17 contributed the most to the variation of specialized metabolites in the biosynthesis pathway of steroidal saponins. This study provides valuable information for further research on the biological functions related to steroidal saponin biosynthesis.

The genome of Dioscorea zingiberensis sheds light on the biosynthesis, origin and evolution of the medicinally important diosgenin saponins

“…Gene duplication can help plants acquire more gene copies, which may lead to new gene functions that are more adaptable than those of single-copy or low-copy genes [ 35 ], and this also applies to D. zingiberensis and other Dioscorea plants containing diosgenin saponins. For example, sterol side-chain catalytic genes (such as CYP90B , CYP94 , and CYP72A ) played important roles in the synthesis of diosgenin saponins [ 25 , 46 , 47 ]. We found that the CYP90B genes in plants without diosgenin saponins were involved in catalyzing the conversion of cholesterol to 22S-hydroxycholesterol, en route to brassinosteroid hormones, while in plants with diosgenin saponins, such as Dioscorea and Paris , some CYP90B genes produced by duplication evolved sterol 16,22-polyhydroxylase activity, leading to the biosynthesis of the core structure of diosgenin [ 24 , 25 ].…”

“…We found that the CYP90B genes in plants without diosgenin saponins were involved in catalyzing the conversion of cholesterol to 22S-hydroxycholesterol, en route to brassinosteroid hormones, while in plants with diosgenin saponins, such as Dioscorea and Paris , some CYP90B genes produced by duplication evolved sterol 16,22-polyhydroxylase activity, leading to the biosynthesis of the core structure of diosgenin [ 24 , 25 ]. Although some studies have shown that CYP72A genes in plants are usually involved in plant-specific metabolism and the 13-hydroxylation of gibberellins in plants [ 48 , 49 ], CYP72A genes identified from diosgenin saponin-containing plants have been shown to be involved in the biosynthesis of diosgenin saponins [ 23 , 24 , 47 ].…”

“…To determine diosgenin saponin and diosgenin contents in Dioscorea plants, the metabolites were extracted from the fresh and young leaves from all 13 Dioscorea species with reference to the established protocol [ 18 , 24 , 47 ]. The relative contents of diosgenin and diosgenin saponins in different Dioscorea species were measured by LC–MS as described below.…”

Comparative transcriptome analysis reveals key genes for polyphyllin difference in five Paris species

“…According to previous research, cholesterol and β ‐sitosterol may be the crucial biosynthetic precursor to polyphyllins as they have similar carbon skeletons than steroidal saponin (Hou, Yuan, et al, 2021). The content of polyphyllins in PPY rhizomes was higher than in leaves, which was consistent with previous research (Gao et al, 2020).…”

“…Primers of key genes are listed in Table S1. According to the method of Hou, Yuan, et al (2021), the qRT‐PCR reaction was performed in triplicate on the CFX96 Real‐Time PCR Detection System (Bio‐Rad). ACTIN was used as the reference gene and the relative expression of key genes was calculated by the 2 −ΔΔCt (Schmittgen & Livak, 2008).…”