Plant Molecular Biology 45: 567–576, 2001.
© 2001 Kluwer Academic Publishers. Printed in the Netherlands.
Expression and activity of cell-wall-degrading enzymes in the latex of
opium poppy, Papaver somniferum L.
Innes Pilatzke-Wunderlich and Craig L. Nessler
Department of Biology, Texas A&M University, College Station, TX 77843-3258, USA;
Present address: Depart-
ment of Plant Pathology, Physiology, and Weed Science, Virginia Polytechnic Institute and State University, 413
Price Hall, Blacksburg, VA 24061-0331, USA (
author for correspondence; e-mail: firstname.lastname@example.org)
Received 27 April 2000; accepted in revised form 20 October 2000
Key words: cell wall degradation, opium, Papaver somnferum
The alkaloid-rich latex of the opium poppy, Papaver somniferum L., is valued as a source of pharmaceuticals
including thebaine, codeine, and morphine, but is also harvested for heroin production. The poppy laticifer sys-
tem develops through the gradual disappearance of the common walls between differentiating laticifer elements
throughout the plant. Gene homologues for cell-wall-degrading enzymes were found during random sequencing
of an opium poppy latex cDNA library. RNA gel blot analysis of cellulase, polygalacturonase β-subunit, 1,3-β-
glucanase, and xyloglucanendotransglycosylasehomologues showed their expression was not limited to laticifers.
In contrast, poppy gene homologues to pectin methylesterase (PME), pectin acetylesterase (PAE) and pectate lyase
(PL) where all highly expressed and latex-speciﬁc. Enzyme assays conﬁrmed the presence of PME, PAE, and PL
activities in latex serum. The abundance of transcripts encoding pectin-degrading enzymes in latex suggests that
these enzymes may play an important role in laticifer development.
The medicinal value of the opium poppy, Papaver
somniferum L., has been recognized for centuries.
Two methods are currently used to harvest pharma-
ceutically active alkaloids from poppies. The modern,
mechanized process involves solvent extraction of al-
kaloids from ﬁeld-dried plants or poppy straw, while
the traditional method still uses the air-dried latex ex-
uded from manually lanced capsules (Bryant, 1988).
In addition to being labor-intensive, a major disad-
vantage of the traditional harvesting method is that
repeated lancings can be made from a single crop.
These ‘second harvests’ are difﬁcult to track and can
easily be diverted into illegal drug production.
Poppy laticifers are classiﬁed as articulated and
anastomosing because of their compound origin and
the perforations that develop between the lateral walls
of adjacent latex vessels (Esau, 1965). Laticifers ac-
company the phloem throughout the plant, but are
most abundant in the ovary where they produce a pe-
ripheral network running in conjunction with the vas-
cular bundles. Interconnections between the strands,
the anastomoses, aid in making the network denser
as the capsule develops (Fahn, 1990). As a result, the
capsule is the most concentrated source of latex, and
therefore alkaloids, in the poppy plant.
Laticifers release latex when damaged because
their cellular contents are underpositive pressure simi-
lar to phloem cells (Esau, 1965; Fahn, 1990). The long
continuous network of laticifer cells allows volumes
of latex to be released with each lancing, making the
collection of opium possible. By understanding the
development of the articulated laticifer in the opium
poppy, it may be possible to prevent the perforations
between initials. Licit producers of opiates would still
have the option of using poppy straw for extraction
and would be better able to ensure that their poppies
are only used to supply the pharmaceutical market.
The process of cell wall perforation in the articu-
lated laticifers of P. somniferum has been analyzed by
electron microscopy (Thureson-Klein, 1970; Nessler