Fig. 1. Monolignol pathway metabolite levels in the C. hassleriana seed coat.

(A) Simplified scheme of pathways to G-, H-, S-, and C-lignins. Lignin synthesis in the Cleome seed coat switches from G-lignin to C-lignin between 12 and 14 DAP. Enzymes are as follows: PAL, l-phenylalanine ammonia-lyase; C4H, cinnamate 4-hydroxylase; C3H, coumarate 3-hydroxylase; 4CL, 4-coumarate: CoA ligase; HCT, hydroxycinnamoyl CoA: shikimate/quinate hydroxycinnamoyl transferase; C3′H, 4-coumaroyl shikimate 3′-hydroxylase; CSE, caffeoyl shikimate esterase; CCoAOMT, caffeoyl CoA 3-O-methyltransferase; COMT, caffeic acid/5-hydroxyconiferaldehyde 3-O-methyltransferase; CCR, cinnamoyl-CoA reductase; CAD, cinnamyl alcohol dehydrogenase; F5H, ferulate/coniferaldehyde 5-hydroxylase. Conversion of phenyalanine to caffeoyl CoA is common to the biosynthesis of both G- and C-lignin. S-lignin is not made as a result of lack of expression of F5H in the seed coat. H-lignin synthesis stops after 12 DAP, resulting in less than 1 μmol/g dry weight (DW) (~0.25% of total lignin). O-methyltransferases that are down-regulated at the onset of C-lignin biosynthesis are shown in red. For a scheme showing all potential routes to G- and C-lignin, see (32). (B) Levels of monolignol pathway intermediates, as determined by targeted LC-MS analysis, at 8 (G-lignin produced) and 16 (C-lignin produced) DAP. Approximately 100 mg of seed coats isolated from seeds harvested from one individual Cleome plant was counted as one biological replicate. Data are means ± SE derived from three biological replicates.