Proposed flavonoid and monolignol biosynthetic pathways in grasses. PTAL, l-phenylalanine/l-tyrosine ammonia-lyase; PAL, l-phenylalanine ammonia-lyase; C4H, cinnamate 4-hydroxylase; 4CL, 4-hydroxycinnamate:CoA ligase; F3ʹH, flavonoid 3ʹ-hydroxylase; FOMT, flavonoid O-methyltransferase; F2H, flavanone 2-hydroxylase; CGT, C-glycosyltransferase; DHT, dehydratase; C3H, p-coumarate 3-hydroxylase; APX, ascorbate peroxidase; HCT, p-hydroxycinnamoyl-CoA:quinate/shikimate hydroxycinnamoyl transferase; C3′H, p-coumaroyl ester 3-hydroxylase; CSE, caffeoyl shikimate esterase; CCoAOMT, caffeoyl-CoA OMT; CAld5H, coniferaldehyde 5-hydroxylase; CCR, cinnamoyl-CoA reductase; CAD, cinnamyl alcohol dehydrogenase; PMT, p-coumaroyl-CoA:monolignol transferase; LAC, laccase; PRX, peroxidase. In purple: flavonoid biosynthetic pathway. In blue: monolignol biosynthetic pathway. Thick arrow: enhancer activity.