The first multi-tissue genome-scale metabolic model of a woody plant highlights suberin biosynthesis pathways in Quercus suber
Fig 4
Biosynthetic pathway of suberin, waxes, and lignin monomers.
Reactions not available at KEGG are highlighted in red. The components of suberin, lignin, and waxes are underlined. The C:16 and C:18 fatty acids produced in the plastid are transported to the endoplasmic reticulum, where they can be elongated and unsaturated, and follow the suberin monomer biosynthesis pathway. Cytochromes P450 (CYPs), peroxygenases, epoxy hydroxylases, ω-oxo-fatty acid dehydrogenases, and ω-hydroxy-fatty acid dehydrogenases catalyse successive reactions to produce the aliphatic monomers. Farnesyl diphosphate, produced from isopentenyl diphosphate provided by the cytosolic mevalonate (MVA) pathway or by the plastidic methylerythritol phosphate (EMP) pathway is used as the initial precursor of steroids in the ER. 2,3-Epoxysqualene is converted into sterols and terpenoids, monomers of the wax component of the phellogen. The phenylpropanoid pathway uses phenylalanine produced in the leaf’s chloroplasts, to produce cinnamate. The pathway follows in the cytosolic surface of the endoplasmic reticulum, and then in the cytosol, producing the lignin monomers. 4CL– 4-Coumarate CoA ligase, AMO: β-amyrin monooxygenase, C3H: p-coumarate 3-hydroxylase, C4H: cinnamate 4-hydroxylase, CAD: cinnamyl alcohol dehydrogenase, CCR: cinnamoyl-CoA reductase, COMT: Caffeoyl-CoA O-methyltransferase, EH: epoxide hydroxylase, FDFT: farnesyl diphosphate farnesyltransferase, FS: friedelin synthase, HFADH: ω-hydroxy-fatty acid dehydrogenase, LS—lupeol synthase, OFADH: ω-oxo-fatty acid dehydrogenase, PAL: phenylalanine ammonia-lyase, PO: peroxygenase, SQE: squalene monooxygenase. A. thaliana identifiers were used for the nomenclature of CYPs for convenience. The IDs of the reactions catalysed by these enzymes can be found in Table L in S2 File.