Comparative Transcriptomic Analysis of Pyrethrin and EβF Biosynthesis in Tanacetum cinerariifolium Stems and Flowers

Tanacetum cinerariifolium, a perennial Asteraceae plant, is renowned for its ornamental value and natural insecticidal compounds, especially pyrethrins. These compounds, primarily stored in flower heads, are highly effective as insecticides with low toxicity to mammals, making them crucial for organic agriculture, along with the sesquiterpene (E)-β-farnesene (EβF), play critical roles in T. cinerariifolium defense mechanisms. However, the spatiotemporal patterns of these secondary metabolites in stems and flower heads, as well as their regulatory mechanisms, remain unclear. This study investigated the biosynthesis and regulation of pyrethrins and EβF across developmental stages (S1–S4) in flowers and stems using GC-MS and transcriptomics. Transcriptome analysis revealed that the expression of pyrethrin biosynthetic genes was not synchronized with pyrethrin accumulation. The main pyrethrin biosynthetic genes exhibited coordinated expression patterns, peaking during early flowering stages (S1–S2), while pyrethrin accumulation was primarily observed during mid-flower development. In contrast, the biosynthetic genes of EβF showed synchronized expression with EβF accumulation, with the highest activity observed in stems and early flowers. WGCNA identified jasmonic acid signaling, trichome differentiation, and terpene transport pathways as potentially associated with pyrethrin biosynthesis. Hub genes including MYC2 were identified as playing pivotal roles in regulating secondary metabolite biosynthesis. These findings provide new insights into the regulation and biosynthesis of pyrethrins and EβF, offering a foundation for optimizing bioactive compound production and advancing sustainable pest management strategies.