Transcriptomic and Metabolomic Insights into Benzylisoquinoline Alkaloid Biosynthesis in Goldthread (Coptis trifolia)

TL;DR

This study explores how goldthread plants make certain chemicals called benzylisoquinoline alkaloids by analyzing their genes and metabolites in leaves and roots.

Contribution

The study identifies 37 BIA-related genes and provides comparative genomic resources for Coptis trifolia and related species.

Findings

Most BIA-related genes are more active in roots than leaves.

Roots accumulate higher levels of BIA compounds like epiberberine.

A single SPS gene in C. trifolia may perform multiple enzymatic functions.

Abstract

Coptis trifolia (threeleaf goldthread) offers a valuable comparative system for investigating the evolution and regulation of benzylisoquinoline alkaloid (BIA) synthesis. In this study, we analyzed the leaf and root transcriptomes of C. trifolia using both long-read and short-read RNA-Sequencing. We assembled 41,926 unigenes (≥500 bp) and identified 37 genes related to BIA biosynthesis, including two transcription factors, bHLH1 and WRKY1. The number of BIA genes identified in C. trifolia was comparable to that in other Coptis species. Transcriptome analysis revealed that most of these genes were more highly expressed in roots than leaves. Consistent with previous studies, C. trifolia contained a single (S)-stylopine synthase (SPS) gene homolog, potentially multifunctional for (S)-canadine synthase (CAS), (S)-cheilanthifoline synthase (CFS), and SPS. Transcriptome and untargeted metabolomic data indicated greater variation in root samples than leaf samples, although slightly more differentially expressed transcripts and metabolites were observed in leaves. Targeted metabolite profiling showed higher BIA accumulation in roots, with epiberberine being the most abundant, followed by coptisine, berberine, and columbamine. These results provide essential genomic resources for comparative analysis of the BIA pathway across Ranunculaceae, targeted gene function studies for metabolic bioengineering, and conservation strategies for C. trifolia, a member of an early-diverging clade within the genus with limited genetic resources.

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