Biosynthetic pathways of hydroxylated cinnamic acids and cinnamoyl CoA thioesters for the formation of lignin and other phenylpropanoids. C4H, cinnamate 4-hydroxylase; C3H, 4-coumarate 3-hydroxylase; OMT, O-methyltransferase; F5H, ferulate 5-hydroxylase; Pt4CL1 and 2, P. tremuloides 4CL1 and 2; CCR, cinnamoyl-CoA reductase; CAD, cinnamyl alcohol dehydrogenase.