Fig. 1

Lignin biosynthesis. The red box shows the pentose phosphate pathway, the orange box shows the shikimate pathway and the synthesis of the aromatic amino acid phenylalanine, the green box shows the general phenylpropanoid pathway and the blue box shows the monolignol specific pathway. Dotted arrows indicate more than one (enzymatic) conversion. In blue are the mutant alleles studied, in green 5-hydroxyconiferyl alcohol, that upon incorporation in lignin, gives rise to 5-hydroxyguaiacyl units. 4CL 4-coumarate:CoA ligase, 6PGD 6-phosphogluconate dehydrogenase, ADT arogenate dehydratase, AT amino transferase, C3H P-coumarate 3-hydroxylase, C4H cinnamate 4-hydroxylase, CAD cinnamyl alcohol dehydrogenase, CCoAOMT caffeoyl-COA O-methyltransferase, CCR cinnamoyl-CoA reductase, CM chorismate mutase, COMT caffeic acid O-methyltransferase, CS chorismate synthase, CSE caffeoyl shikimate esterase, DHQD/SD 3-dehydroquinate dehydratase/shikimate dehydrogenase, DHS 3-deoxy-d-arabino-heptulosonate 7-phosphate synthase, DQS 3-dehydroquinate synthase, EPSPS 5-enolpyruvylshikimate-3-phosphate synthase, F5H ferulate 5-hydroxylase, G6PD glucose-6-phosphate dehydrogenase, HCT hydroxycinnamoyl-COA shikimate/quinate hydroxycinnamoyl transferase, HPI hexose phosphate isomerase, PAL penylalanine ammonia-lysase, PDT prephenate dehydratase, RPE ribose-5-phosphate epimerase, RPI ribose-5-phosphate isomerase, SK shikimate kinase, SOL3 6-gluconolactonase, TKT transketolase, TRA transaldolase