These authors contributed equally to this work.
The role of phloem sieve elements and laticifers in the biosynthesis and accumulation of alkaloids in opium poppy†
Article first published online: 30 JUN 2006
The Plant Journal
Volume 47, Issue 4, pages 547–563, August 2006
How to Cite
Samanani, N., Alcantara, J., Bourgault, R., Zulak, K. G. and Facchini, P. J. (2006), The role of phloem sieve elements and laticifers in the biosynthesis and accumulation of alkaloids in opium poppy. The Plant Journal, 47: 547–563. doi: 10.1111/j.1365-313X.2006.02801.x
Dedicated to the memory of Vincent R. Franceschi.
- Issue published online: 10 JUL 2006
- Article first published online: 30 JUN 2006
- Received 12 March 2006; revised 17 April 2006; accepted 19 April 2006.
- benzylisoquinoline alkaloids;
- immunofluorescence labeling;
- immunogold labeling;
- in situ hybridization;
- Papaver somniferum;
- secondary metabolism
The benzylisoquinoline alkaloids of opium poppy, including the narcotic analgesics morphine and codeine, accumulate in the multinucleate cytoplasm of specialized laticifers that accompany vascular tissues throughout the plant. In mature opium poppy plants, immunofluorescence labeling using specific antibodies showed that four alkaloid biosynthetic enzymes, (S)-norcoclaurine 6-O-methyltransferase (6OMT), (S)-coclaurine N-methyltransferase (CNMT), (S)-3′-hydroxy-N-methylcoclaurine-4′-O-methyltransferase (4′OMT) and salutaridinol-7-O-acetyltransferase (SAT) were restricted to sieve elements of the phloem adjacent or proximal to laticifers. The identity of sieve elements was confirmed by (i) the specific immunogold labeling of the characteristic cytoplasm of this cell type, (ii) the co-localization of a sieve element-specific H+-ATPase with all biosynthetic enzymes and (iii) the strict association of sieve plates with immunofluorescent cells. The localization of laticifers was demonstrated antibodies specific to major latex protein (MLP), which is characteristic of this cell type. In situ hybridization using antisense RNA probes for 6OMT, CNMT, 4′OMT and SAT showed that the corresponding gene transcripts were found in the companion cell paired with each sieve element. Seven benzylisoquinoline alkaloid biosynthetic enzymes, (S)-N-methylcoclaurine 3′-hydroxylase (CYP80B1), berberine bridge enzyme, codeinone reductase, 6OMT, CNMT, 4′OMT and SAT were localized by immunofluorescence labeling to the sieve elements in the root and hypocotyl of opium poppy seedlings. The abundance of these enzymes increased rapidly between 1 and 3 days after seed germination. The localization of seven biosynthetic enzymes to the sieve elements provides strong support for the unique, cell type-specific biosynthesis of benzylisoquinoline alkaloids in the opium poppy.