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. 2024 Jul 24;76(1):35–51. doi: 10.1093/jxb/erae317

Fig. 3.

Fig. 3.

Schematic illustration of the cellular localization of morphine biosynthesis in opium poppy. (A) Morphine biosynthesis involves three cell types: companion cells (cc), sieve elements (se), and laticifers (la) of the phloem system. (B) The enzymes synthesized in companion cells are transported to sieve elements (black horizontal arrows) through plasmodesmata. The intermediate compounds of salutaridine and thebaine are transferred from sieve elements to latifer cells (red horizontal arrows) through apoplast by a family of benzylisoquinoline uptake permeases (BUPs). The enzymes required for the final stages of alkaloid biosynthesis are mainly localized in laticifers. Transcripts and proteins primarily detected in each cell type are shown in black italic and in blue, respectively. vc, vascular cambium; pp, phloem parenchyma; xy, xylem vessels. 4ʹOMT, 3ʹ-hydroxyl-N-methylcoclaurine 4ʹ-O-methyltransferase; 6OMT, norcoclaurine 6-O-methyltransferase; CNMT, coclaurine N-methyltransferase; CODM, codeine O-demethylase; COR, codeinone reductase; NCS, norcoclaurine synthase; NISO, neopinone isomerase; NMCH, N-methylcoclaurine 3ʹ-hydroxylase; REPI, reticuline epimerase; SalAT, salutaridinol 7-O-acetyltransferase; SalR, salutaridine reductase; SalSyn, salutaridine synthase; T6ODM, thebaine 6-O-demethylase; THS, thebaine synthase (Liscombe and Facchini, 2008; Lee et al., 2013; Beaudoin and Facchini, 2014; Ozber and Facchini, 2022).