Abstract

BackgroundMembers of the cytochrome P450 (CYP450) and UDP-glycosyltransferase (UGT) gene superfamily have been shown to play essential roles in regulating secondary metabolite biosynthesis. However, the systematic identification of CYP450s and UGTs has not been reported in Aralia elata (Miq.) Seem, a highly valued medicinal plant.ResultsIn the present study, we conducted the RNA-sequencing (RNA-seq) analysis of the leaves, stems, and roots of A. elata, yielding 66,713 total unigenes. Following annotation and KEGG pathway analysis, we were able to identify 64 unigenes related to triterpenoid skeleton biosynthesis, 254 CYP450s and 122 UGTs, respectively. A total of 150 CYP450s and 92 UGTs encoding > 300 amino acid proteins were utilized for phylogenetic and tissue-specific expression analyses. This allowed us to cluster 150 CYP450s into 9 clans and 40 families, and then these CYP450 proteins were further grouped into two primary branches: A-type (53%) and non-A-type (47%). A phylogenetic analysis of 92 UGTs and other plant UGTs led to clustering into 16 groups (A-P). We further assessed the expression patterns of these CYP450 and UGT genes across A. elata tissues, with 23 CYP450 and 16 UGT members being selected for qRT-PCR validation, respectively. From these data, we identified CYP716A295 and CYP716A296 as the candidate genes most likely to be associated with oleanolic acid synthesis, while CYP72A763 and CYP72A776 were identified as being the most likely to play roles in hederagenin biosynthesis. We also selected five unigenes as the best candidates for oleanolic acid 3-O-glucosyltransferase. Finally, we assessed the subcellular localization of three CYP450 proteins within Arabidopsis protoplasts, highlighting the fact that they localize to the endoplasmic reticulum.ConclusionsThis study presents a systematic analysis of the CYP450 and UGT gene family in A. elata and provides a foundation for further functional characterization of these two multigene families.

Highlights

  • Members of the cytochrome P450 (CYP450) and UDP-glycosyltransferase (UGT) gene superfamily have been shown to play essential roles in regulating secondary metabolite biosynthesis

  • A. elata is ideal for the study of the biosynthesis of triterpenoid saponins, and in particular those of hederagenin and oleanane-types

  • The leaves of A. elata have been found to contain the largest quantity of these saponins, with progressively lower levels found in root and stem tissues

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Summary

Introduction

Members of the cytochrome P450 (CYP450) and UDP-glycosyltransferase (UGT) gene superfamily have been shown to play essential roles in regulating secondary metabolite biosynthesis. Aralia elata (Miq.) Seem is a member of the Araliaceae family and grows widely throughout Korea, Japan, Russia, and China, where it is used as both a food and a medicinal plant [1]. Owing to their unique taste, young A. elata shoots are commonly eaten in many regions of Asia [2]. A number of distinct triterpene saponins (chikusetsusaponins Iva and IV and aralosides A, B, V, VII, and X) have been isolated from the leaves [7, 8] and root bark [9, 10]. A. elata is ideal for the study of the biosynthesis of triterpenoid saponins, and in particular those of hederagenin and oleanane-types

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