Pj. Facchini et Da. Bird, DEVELOPMENTAL REGULATION OF BENZYLISOQUINOLINE ALKALOID BIOSYNTHESIS IN OPIUM POPPY PLANTS AND TISSUE-CULTURES, In vitro cellular & developmental biology. Plant, 34(1), 1998, pp. 69-79
Opium poppy (Papaver somniferum L.) contains a number of pharmaceutica
lly important alkaloids of the benzylisoquinoline type including morph
ine, codeine, papaverine, and sanguinarine. Although these alkaloids a
ccumulate to high concentrations in various organs of the intact plant
, only the phytoalexin sanguinarine has been found at significant leve
ls in opium poppy cell cultures. Moreover, even sanguinarine biosynthe
sis is not constitutive in poppy cell suspension cultures, but is typi
cally induced only after treatment with a fungal-derived elicitor. The
absence of appreciable quantities of alkaloids in dedifferentiated op
ium poppy cell cultures suggests that benzylisoquinoline alkaloid bios
ynthesis is developmentally regulated and requires the differentiation
of specific tissues. In the 40 yr since opium poppy tissues were firs
t cultured in. vitro, a number of reports on the redifferentiation of
roots and buds from callus have appeared. A requirement for the presen
ce of specialized laticifer cells has been suggested before certain al
kaloids, such as morphine and codeine, can accumulate. Laticifers repr
esent a complex internal secretory system in about 15 plant families a
nd appear to have multiple evolutionary origins. Opium poppy laticifer
s differentiate from procambial cells and undergo articulation and ana
stomosis to form a continuous network of elements associated with the
phloem throughout much of the intact plant. Latex is the combined cyto
plasm of fused laticifer vessels, and contains numerous large alkaloid
vesicles in which latex-associated poppy alkaloids are sequestered. T
he formation of alkaloid vesicles, the subcellular compartmentation of
alkaloid biosynthesis, and the tissue-specific localization and contr
ol of these processes are important unresolved problems in plant cell
biology. Alkaloid biosynthesis in opium poppy is an excellent model sy
stem to investigate the developmental regulation and cell biology of c
omplex metabolic pathways, and the relationship between metabolic regu
lation and cell-type specific differentiation. La this review, we summ
arize the literature on the roles of cellular differentiation and plan
t development in alkaloid biosynthesis in opium poppy plants and tissu
e cultures.