Integrated transcriptomic and metabolomic analysis identifies key regulatory genes involved in lignin biosynthesis in Heracleum moellendorffii.

Abstract

Lignin is a major component of secondary cell walls and plays essential roles in mechanical support and stress resistance. In Heracleum moellendorffii Hance, a medicinal and aromatic plant resource under artificial cultivation, petioles undergo progressive firming and lignification during development. Here, we combined anatomical observation, cell-wall and biochemical measurements, metabolomics, transcriptomics, and heterologous functional analysis to characterize developmental lignification. Microscopic observations and firmness measurements revealed progressive structural changes accompanied by increased lignin deposition from the early to late developmental stages. Targeted metabolite analysis showed developmental remodeling of the monolignol-related metabolite pool, with the relative proportion of coniferyl alcohol increasing during petiole maturation. Integrated RNA-seq and metabolite analyses prioritized Hm4CL2, HmCCR2, and HmCAD2 as candidate structural genes associated with lignin biosynthesis. Stable heterologous expression of these genes in tobacco was associated with altered vascular anatomy and changes in measured monolignol-related compounds. These findings provide a developmental framework for lignification in H. moellendorffii and identify candidate genes for future manipulation of lignification, pending direct functional validation in this species.

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