Objective This study investigated the regulatory mechanism by which methyl jasmonate (MeJA) modulates triterpenoid saponin biosynthesis in Jixuecao (Centella asiatica). Methods Plants were treated with 200 μmol/L MeJA, and temporal changes in leaf asiaticoside and madecassoside contents were quantified by high-performance liquid chromatography (HPLC). Transcriptome data were analyzed using weighted gene co-expression network analysis (WGCNA) to identify modules significantly correlated with asiaticoside accumulation, followed by Mfuzz clustering to refine gene subclusters. Expression patterns of candidate key genes were validated by quantitative real-time PCR (qRT-PCR). Results MeJA treatment markedly promoted asiaticoside and madecassoside accumulation, increasing their contents by 18.28% and 14.58%, respectively. WGCNA revealed 33 co-expression modules, with the darkred module displaying a highly significant positive correlation with asiaticoside content (P < 0.01). Mfuzz clustering subdivided the 286 genes in this module into four subclusters; Notably, 239 genes in Clusters 1-3 were significantly enriched in the terpenoid backbone biosynthesis, sesquiterpenoid biosynthesis, and triterpenoid biosynthesis pathways. Twenty-eight structural genes directly involved in asiaticoside synthesis were identified, exhibiting expression profiles closely aligned with saponin accumulation. qRT-PCR confirmed significant MeJA-induced upregulation of 11 key structural genes associated with triterpenoid backbone synthesis and modification, consistent with the transcriptome findings. Conclusion MeJA enhances triterpenoid saponin biosynthesis in C. asiatica through coordinated upregulation of these 11 key structural genes within the darkred module. By integrating multi-omics profiling with experimental validation, this work systematically elucidates the molecular mechanisms underlying MeJA-induced triterpenoid saponin accumulation, offering valuable candidate genes for future functional characterization and genetic enhancement of C. asiatica.

Centella asiatica (L.) Urban  /  MeJA  /  asiaticoside  /  structural gene  /  WGCNA