AsAP2 transcriptionally activates ferulate 5-hydroxylase, diverting ferulic acid metabolism toward lignin biosynthesis in Angelica sinensis.

Premature flowering in Angelica sinensis (Danggui) triggers severe declines in root yield and medicinal quality5 by reducing bioactive ferulic acid and promoting lignification. Ferulate 5-hydroxylase (F5H), a cytochrome P450 enzyme, drives metabolic flux toward lignin biosynthesis, but its regulatory network and functional dynamics during early flowering remain unresolved. Transcriptomic and functional analyses identified AsF5H (As09G05225) as a key gene upregulated in early-flowering plants, correlating with root lignin accumulation and ferulic acid depletion. Phylogenetic studies confirmed F5H functional conservation across Apiaceae species, while heterologous expression in yeast validated its enzymatic activity in converting ferulic acid to 5-hydroxyferulic acid. Structural modeling pinpointed three substrate-binding residues (ARG98, ALA115, PHE116) critical for regiospecific hydroxylation. Through correlation network analysis, we identified the AP2/ERF transcription factor AsAP2 (As08G00463) as a regulator of AsF5H and support this regulation with transient assay in tobacco. Our findings elucidate a molecular trade-off between lignification and medicinal compound accumulation, providing actionable targets for metabolic engineering or breeding programs to suppress premature flowering effects and enhance root quality in commercial Danggui cultivation.