Multi‐site genetic modulation of monolignol biosynthesis suggests new routes for formation of syringyl lignin and wall‐bound ferulic acid in alfalfa (Medicago sativa L.)

摘要: †Summary Genes encoding seven enzymes of the monolignol pathway were independently downregulated in alfalfa (Medicago sativa) using antisense and/or RNA interference. In each case, total flux into lignin was reduced, with largest effects arising from downregulation earlier pathway. The L-phenylalanine ammonia-lyase, 4-coumarate 3-hydroxylase, hydroxycinnamoyl CoA quinate/ shikimate transferase, ferulate 5-hydroxylase or caffeic acid 3-O-methyltransferase resulted compositional changes and wall-bound hydroxycinnamic acids consistent current models However, downregulating caffeoyl neither reduced syringyl (S) units nor ferulate, inconsistent a role for this enzyme 3-O-methylation ofS precursors acids. Paradoxically, composition differed plants either cinnamate 4-hydroxylase phenylalanine ammonia-lyase. No levels acylated flavonoids observed various transgenic lines. model biosynthesis appears to be an over-simplification, at least alfalfa, additional may needed reactions S biosynthesis.