Metabolome and Transcriptome Analysis Reveals the Transcriptional Regulatory Mechanism of Triterpenoid Saponin Biosynthesis in Soapberry (Sapindus mukorossi Gaertn.)

Abstract

Soapberry (Sapindus mukorossi Gaertn.) pericarps are rich in valuable bioactive triterpenoid saponins. However, the saponin content dynamics and the molecular regulatory network of saponin biosynthesis in soapberry pericarps remain largely unclear. Here, we performed combined metabolite profiling and transcriptome analysis to identify saponin accumulation kinetic patterns, investigate gene networks, and characterize key candidate genes and transcription factors (TFs) involved in saponin biosynthesis in soapberry pericarps. A total of 54 saponins were tentatively identified, including 25 that were differentially accumulated. Furthermore, 49 genes putatively involved in sapogenin backbone biosynthesis and some candidate genes assumed to be responsible for the backbone modification, including 41 cytochrome P450s and 45 glycosyltransferases, were identified. Saponinspecific clusters/modules were identified by Mfuzz clustering and weighted gene coexpression network analysis, and one TF−gene regulatory network underlying saponin biosynthesis was proposed. The results of yeast one-hybrid assay and electrophoretic mobility shift assay suggested that SmbHLH2, SmTCP4, and SmWRKY27 may play important roles in the triterpenoid saponin biosynthesis by directly regulating the transcription of SmCYP71D-3 in the soapberry pericarp. Overall, these findings provide valuable information for understanding the molecular regulatory mechanism of saponin biosynthesis, enriching the gene resources, and guiding further research on triterpenoid saponin accumulation in soapberry pericarps.

Integrative analysis of microRNAs and mRNAs reveals the regulatory networks of triterpenoid saponin metabolism in Soapberry (Sapindus mukorossi Gaertn.)

“…For sRNA sequencing, pericarp samples were collected from three trees. The details of these materials were described in our previous report ( Zhao et al., 2019 ; Xu et al., 2021b ; Xu et al., 2022 ).…”

“…Then, module–trait associations were estimated by calculating the Pearson’s correlations between the MEs and the differentially accumulated saponin (DAS) content obtained from the pericarp materials from the same eight developmental stages determined previously by our group previously ( Table S1 ). Integrative analysis was also performed to determine correlations between miRNA MEs and mRNA MEs from the same samples ( Xu et al., 2022 ). Subsequently, we also performed Pearson’s correlation analysis to detect negatively associated miRNA–mRNA pairs.…”

“…Target gene prediction was performed using the default parameters. In addition, annotation information for these target genes was extracted from the Soapberry Transcriptome Annotation Project (Xu et al, 2022). The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases were used for gene annotation using emapper.py (EggNOG v5.0: http://eggnog5.embl.de/#/app/home) (Hernańdez-Plaza et al, 2022).…”

Physiological and Transcriptional Analysis Provides Insights into Tea Saponin Biosynthesis and Regulation in Response to SA in Camellia vietnamensis Huang

“…In this study, the biosynthesis mechanism of tea saponin in C. vietnamensis was analyzed, and the terpenoids synthesis pathway was studied (Figure S1). There were 49 genes putatively involved in sapogenin biosynthesis, and 54 saponins were identified by transcriptome and metabolome analysis [40]. In the previous study, we also identified some genes (such as SQS) related to the biosynthesis of tea saponins in C. vietnamensis [1].…”

Transcription Factors ZjMYB39 and ZjMYB4 Regulate Farnesyl Diphosphate Synthase- and Squalene Synthase-Mediated Triterpenoid Biosynthesis in Jujube

“…Triterpenoids accumulation is controlled by multiple regulatory mechanisms, including transcriptional regulation and plant phytohormine signaling . The transcriptional level regulation has been considered a major aspect, and transcription factors (TFs) play vital roles in binding to promoters of triterpenoid-related genes to promote their transcription, which affects triterpenoid accumulation. , Although no studies have examined the regulation of triterpenoid biosynthesis by TFs in jujube, studies of the regulatory mechanisms in other species potentially provide some relevant insights. For example, GubHLH3 can positively regulate the key genes of triterpenoid biosynthesis in Glycyrrhiza uralensis …”