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. 2022 Mar 1;13:844622. doi: 10.3389/fgene.2022.844622

FIGURE 8.

FIGURE 8

Genes upstream of the alkaloid biosynthesis pathway in Dendrobium nobile, adapted from Pu (Pu et al., 2021) and Wang (Wang et al., 2020). In the methylerythritol phosphate (MEP) pathway, there are seven consecutive steps catalyzed by the following enzymes: DXS, 1-deoxy-D-xylulose 5-phosphate (DXP) synthase; DXR, DXP-reductoisomerase; MCT, 2-C-methyl-D-erythritol 4-phosphate cytidylyltransferase; CMK, 4-(cytidine 5′-diphospho)-2-C-methyl-D-erythritol kinase; MDS, 2-C-methyl-D-erythritol 2,4-cyclodiphosphate synthase; HDS, 4-hydroxy-3-methylbut-2-enyldiphosphate (HMBPP) synthase; and HDR, HMBPP reductase. The mevolonate (MVA) pathway contains ACCT, acetyl-coenzyme A (CoA) C-acetyltransferase; HMGS, HMG-CoA synthase; HMGR, HMG-CoA reductase; MVK, mevalonic acid kinase; PMK, phosphomevalonate kinase; and MVD, mevalonate-5-diphosphate decarboxylase. The shikimate pathway contains DHS, 3-dexoy-7-phosphoheptulonate synthase; DHQS, 3-dehydroquinate synthase; DHD, 3-dehydroquinate dehydratase; SKDH, shikimate dehydrogenase; SK, shikimate kinase; SHKG, 3-phosphoshikimate 1-carboxyvinyltransferase; and CS, chorismate synthase. The red five-pointed stars show higher gene expression in stems than in leaves. The dashed lines indicate multiple steps.