Investigation of abiogenic stress-induced alterations in the level of secondary metabolites in poppy plants (Papaver somniferum L.)

We aimed to understand the effects of water stress on the alkaloid production in various developmental stages of poppy plants and the effect of stress on the alkaloids content in the capsules. Three stages of the life cycle of Papaver somniferum L. were selected in our studies: Rosette, Flowering and Lancing developmental stages. Four types of water conditions were examined: Control, Withdrawal of Water, 50% Water Supply and Inundation. The morphological monitoring, results of Relative Water Content and proline content were used as indicators of stress. The result of the measurements in poppy leaves show that the secondary metabolites dramatically respond to these stress conditions. The constant water supply was beneficial for the accumulation of alkaloids in the capsules.

Quantitative 1H nuclear magnetic resonance metabolite profiling as a functional genomics platform to investigate alkaloid biosynthesis in opium poppy

Opium poppy (Papaver somniferum) produces a diverse array of bioactive benzylisoquinoline alkaloids and has emerged as a versatile model system to study plant alkaloid metabolism. The plant is widely cultivated as the only commercial source of the narcotic analgesics morphine and codeine. Variations in plant secondary metabolism as a result of genetic diversity are often associated with perturbations in other metabolic pathways. As part of a functional genomics platform, we used (1)H nuclear magnetic resonance (NMR) metabolite profiling for the analysis of primary and secondary metabolism in opium poppy. Aqueous and chloroform extracts of six different opium poppy cultivars were subjected to chemometric analysis. Principle component analysis of the (1)H NMR spectra for latex extracts clearly distinguished two varieties, including a low-alkaloid variety and a high-thebaine, low-morphine cultivar. Distinction was also made between pharmaceutical-grade opium poppy cultivars and a condiment variety. Such phenotypic differences were not observed in root extracts. Loading plots confirmed that morphinan alkaloids contributed predominantly to the variance in latex extracts. Quantification of 34 root and 21 latex metabolites, performed using Chenomx NMR Suite version 4.6, showed major differences in the accumulation of specific alkaloids in the latex of the low-alkaloid and high-thebaine, low-morphine varieties. Relatively few differences were found in the levels of other metabolites, indicating that the variation was specific for alkaloid metabolism. Exceptions in the low-alkaloid cultivar included an increased accumulation of the alkaloid precursor tyramine and reduced levels of sucrose, some amino acids, and malate. Real-time polymerase chain reaction analysis of 42 genes involved in primary and secondary metabolism showed differential gene expression mainly associated with alkaloid biosynthesis. Reduced alkaloid levels in the condiment variety were associated with the reduced abundance of transcripts encoding several alkaloid biosynthetic enzymes.

Opium poppy and Madagascar periwinkle: model non-model systems to investigate alkaloid biosynthesis in plants

Alkaloids represent a large and diverse group of compounds that are related by the occurrence of a nitrogen atom within a heterocyclic backbone. Unlike other types of secondary metabolites, the various structural categories of alkaloids are unrelated in terms of biosynthesis and evolution. Although the biology of each group is unique, common patterns have become apparent. Opium poppy (Papaver somniferum), which produces several benzylisoquinoline alkaloids, and Madagascar periwinkle (Catharanthus roseus), which accumulates an array of monoterpenoid indole alkaloids, have emerged as the premier organisms used to study plant alkaloid metabolism. The status of these species as model systems results from decades of research on the chemistry, enzymology and molecular biology responsible for the biosynthesis of valuable pharmaceutical alkaloids. Opium poppy remains the only commercial source for morphine, codeine and semi-synthetic analgesics, such as oxycodone, derived from thebaine. Catharanthus roseus is the only source for the anti-cancer drugs vinblastine and vincristine. Impressive collections of cDNAs encoding biosynthetic enzymes and regulatory proteins involved in the formation of benzylisoquinoline and monoterpenoid indole alkaloids are now available, and the rate of gene discovery has accelerated with the application of genomics. Such tools have allowed the establishment of models that describe the complex cell biology of alkaloid metabolism in these important medicinal plants. A suite of biotechnological resources, including genetic transformation protocols, has allowed the application of metabolic engineering to modify the alkaloid content of these and related species. An overview of recent progress on benzylisoquinoline and monoterpenoid indole alkaloid biosynthesis in opium poppy and C. roseus is presented.

Microtubules are a target for self-incompatibility signaling in Papaver pollen

Perception and integration of signals into responses is of crucial importance to cells. Both the actin and microtubule cytoskeleton are known to play a role in mediating diverse stimulus responses. Self-incompatibility (SI) is an important mechanism to prevent self-fertilization. SI in Papaver rhoeas triggers a Ca(2+)-dependent signaling network to trigger programmed cell death (PCD), providing a neat way to inhibit and destroy incompatible pollen. We previously established that SI stimulates F-actin depolymerization and that altering actin dynamics can push pollen tubes into PCD. Very little is known about the role of microtubules in pollen tubes. Here, we investigated whether the pollen tube microtubule cytoskeleton is a target for the SI signals. We show that SI triggers very rapid apparent depolymerization of cortical microtubules, which, unlike actin, does not reorganize later. Actin depolymerization can trigger microtubule depolymerization but not vice versa. Moreover, although disruption of microtubule dynamics alone does not trigger PCD, alleviation of SI-induced PCD by taxol implicates a role for microtubule depolymerization in mediating PCD. Together, our data provide good evidence that SI signals target the microtubule cytoskeleton and suggest that signal integration between microfilaments and microtubules is required for triggering of PCD.

Enhancement of alkaloid production in opium and California poppy by transactivation using heterologous regulatory factors

Genes encoding regulatory factors isolated from Arabidopsis, soybean and corn have been screened to identify those that modulate the expression of genes encoding for enzymes involved in the biosynthesis of morphinan alkaloids in opium poppy (Papaver somniferum) and benzophenanthridine alkaloids in California poppy (Eschscholzia californica). In opium poppy, the over-expression of selected regulatory factors increased the levels of PsCOR (codeinone reductase), Ps4'OMT (S-adenosyl-l-methionine:3'-hydroxy-N-methylcoclaurine 4'-O-methyltransferase) and Ps6OMT [(R,S)-norcoclaurine 6-O-methyltransferase] transcripts by 10- to more than 100-fold. These transcriptional activations translated into an enhancement of alkaloid production in opium poppy of up to at least 10-fold. In California poppy, the transactivation effect of regulatory factor WRKY1 resulted in an increase of up to 60-fold in the level of EcCYP80B1 [(S)-N-methylcoclaurine 3'-hydroxylase] and EcBBE (berberine bridge enzyme) transcripts. As a result, the accumulations of selected alkaloid intermediates were enhanced up to 30-fold. The transactivation effects of other regulatory factors led to the accumulation of the same intermediates. These regulatory factors also led to the production of new alkaloids in California poppy callus culture.

Quantitative 1H NMR metabolomics reveals extensive metabolic reprogramming of primary and secondary metabolism in elicitor-treated opium poppy cell cultures

BACKGROUND

Opium poppy (Papaver somniferum) produces a diverse array of bioactive benzylisoquinoline alkaloids and has emerged as a model system to study plant alkaloid metabolism. The plant is cultivated as the only commercial source of the narcotic analgesics morphine and codeine, but also produces many other alkaloids including the antimicrobial agent sanguinarine. Modulations in plant secondary metabolism as a result of environmental perturbations are often associated with the altered regulation of other metabolic pathways. As a key component of our functional genomics platform for opium poppy we have used proton nuclear magnetic resonance (1H NMR) metabolomics to investigate the interplay between primary and secondary metabolism in cultured opium poppy cells treated with a fungal elicitor.

RESULTS

Metabolite fingerprinting and compound-specific profiling showed the extensive reprogramming of primary metabolic pathways in association with the induction of alkaloid biosynthesis in response to elicitor treatment. Using Chenomx NMR Suite v. 4.6, a software package capable of identifying and quantifying individual compounds based on their respective signature spectra, the levels of 42 diverse metabolites were monitored over a 100-hour time course in control and elicitor-treated opium poppy cell cultures. Overall, detectable and dynamic changes in the metabolome of elicitor-treated cells, especially in cellular pools of carbohydrates, organic acids and non-protein amino acids were detected within 5 hours after elicitor treatment. The metabolome of control cultures also showed substantial modulations 80 hours after the start of the time course, particularly in the levels of amino acids and phospholipid pathway intermediates. Specific flux modulations were detected throughout primary metabolism, including glycolysis, the tricarboxylic acid cycle, nitrogen assimilation, phospholipid/fatty acid synthesis and the shikimate pathway, all of which generate secondary metabolic precursors.

CONCLUSION

The response of cell cultures to elicitor treatment involves the extensive reprogramming of primary and secondary metabolism, and associated cofactor biosynthetic pathways. A high-resolution map of the extensive reprogramming of primary and secondary metabolism in elicitor-treated opium poppy cell cultures is provided.

Self-incompatibility in Papaver: signalling to trigger PCD in incompatible pollen

Sexual reproduction in higher plants uses pollination, involving interactions between pollen and pistil. Self-incompatibility (SI) prevents self-fertilization, providing an important mechanism to promote outbreeding. SI is controlled by the S-locus; discrimination occurs between incompatible pollen, which is rejected, while compatible pollen can achieve fertilization. In Papaver rhoeas, S proteins encoded by the pistil part of the S-locus interact with incompatible pollen to effect rapid inhibition of tip growth. This self-incompatible interaction triggers a Ca(2+)-dependent signalling cascade. SI-specific events triggered in incompatible pollen include rapid depolymerization of the actin cytoskeleton; phosphorylation of soluble inorganic pyrophosphatases, and activation of a MAPK. It has recently been shown that programmed cell death (PCD) is triggered by SI. This provides a precise mechanism for the specific destruction of 'self' pollen. Recent data providing evidence for SI-induced caspase-3-like protease activity, and the involvement of actin depolymerization and MAPK activation in SI-mediated PCD will be discussed. These studies not only significantly advance our understanding of the mechanisms involved in SI, but also contribute to our understanding of functional links between signalling components and initiation of PCD in a plant cell. Recent data demonstrating SI-mediated modification of soluble inorganic pyrophosphatases are also described.

Metabolic engineering of morphinan alkaloids by over-expression and RNAi suppression of salutaridinol 7-O-acetyltransferase in opium poppy

We demonstrate that both over-expression and suppression of the gene encoding the morphinan pathway enzyme salutaridinol 7-O-acetyltransferase (SalAT) in opium poppy affects the alkaloid products that accumulate. Over-expression of the gene in most of the transgenic events resulted in an increase in capsule morphine, codeine and thebaine on a dry-weight basis. The transgenic line with the highest alkaloid content had 41%, 37% and 42% greater total alkaloids than the control in three independent trials over 3 years. DNA-encoded hairpin RNA-mediated suppression of SalAT resulted in the novel accumulation of the alkaloid salutaridine at up to 23% of total alkaloid; this alkaloid is not detectable in the parental genotype. Salutaridine is not the substrate of SalAT but the substrate of the previous enzyme in the pathway, salutaridine reductase. RNA transcript analysis of 16 primary T0 transformants and their segregating T1 progeny revealed an average reduction in SalAT transcript to about 12% of the control. Reduction in SalAT transcript was evident in both leaves and latex. Reverse transcriptase PCR and high-performance liquid chromatography analyses confirmed cosegregation of the expressed transgene with the salutaridine accumulating phenotype.

Gene transcript and metabolite profiling of elicitor-induced opium poppy cell cultures reveals the coordinate regulation of primary and secondary metabolism

Elicitor-induced sanguinarine accumulation in opium poppy (Papaver somniferum) cell cultures provides a responsive model system to profile modulations in gene transcripts and metabolites related to alkaloid biosynthesis. An annotated expressed sequence tag (EST) database was assembled from 10,224 random clones isolated from an elicitor-treated opium poppy cell culture cDNA library. The most abundant ESTs encoded defense proteins, and enzymes involved in alkaloid metabolism and S-adenosylmethionine-dependent methyl transfer. ESTs corresponding to 40 enzymes involved in the conversion of sucrose to sanguinarine were identified. A corresponding DNA microarray was probed with RNA from cell cultures collected at various time-points after elicitor treatment, and compared with RNA from control cells. Several diverse transcript populations were coordinately induced, with alkaloid biosynthetic enzyme and defense protein transcripts displaying the most rapid and substantial increases. In addition to all known sanguinarine biosynthetic gene transcripts, mRNAs encoding several upstream primary metabolic enzymes were coordinately induced. Fourier transform-ion cyclotron resonance-mass spectrometry was used to characterize the metabolite profiles of control and elicitor-treated cell cultures. Principle component analysis revealed a significant and dynamic separation in the metabolome, represented by 992 independent detected analytes, in response to elicitor treatment. Identified metabolites included sanguinarine, dihydrosanguinarine, and the methoxylated derivatives dihydrochelirubine and chelirubine, and the alkaloid pathway intermediates N-methylcoclaurine, N-methylstylopine, and protopine. Some of the detected analytes showed temporal changes in abundance consistent with modulations in the profiles of alkaloid biosynthetic gene transcripts.

De novo biosynthesis of morphine in animal cells: an evidence-based model

Recent empirical findings have contributed valuable mechanistic information in support of a regulated de novo biosynthetic pathway for chemically authentic morphine in animal cells, with many similarities to the extensively characterized multi-enzyme plant pathway in opium poppy (Papaver somniferum). The present review elaborates an evidence-based model of cellular morphine expression that reflects a coalescence of these recent biochemical data with historical data gleaned from over thirty years of neurochemical/neuropharmacological investigation into the etiology and biological significance of dopamine (DA)-related heterocyclic conjugate molecules, termed tetrahydroisoquinoline (TIQ) or benzylisoquinoline (BIQ) alkaloids, and with outstanding work completed over the last decade that has elucidated biochemical and molecular bases of morphine and related isoquinoline alkaloid expression in plant systems. In essence, we are now afforded a rare window of opportunity to firmly establish essential biochemical linkages between plant and animal biosynthetic pathways that have been conserved throughout evolution.

Honeybees foraging response in genetically diversified opium poppy

Studies were carried out on honeybees foraging on plant flowers. Results showed significantly higher foraging response of honeybees (Apis mellifera) in genetically divergent narcotic plant opium poppy (Papaver somniferum). Of the 18 mutants and two locally adapted cultivars of diverse genotypes screened, eight revealed significantly greater foraging response manifesting honeybee's preference towards specific plant morphotypes. The number of flower bloom did not correspond to number of foraging bees in both mutant and cultivar plant types of opium poppy. The genotype specific foraging response of honeybees could be attributed to physico-chemical properties of opium poppy flowers. This could have implications for the development of opium alkaloid fortified honeys for novel pharmaceuticals and isolation of natural spray compounds to attract honeybee pollinators for promoting crossing and sustainable hybridity in crops.

The role of phloem sieve elements and laticifers in the biosynthesis and accumulation of alkaloids in opium poppy

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.

Actin depolymerization is sufficient to induce programmed cell death in self-incompatible pollen

Self-incompatibility (SI) prevents inbreeding through specific recognition and rejection of incompatible pollen. In incompatible Papaver rhoeas pollen, SI triggers a Ca²⁺ signaling cascade, resulting in the inhibition of tip growth, actin depolymerization, and programmed cell death (PCD). We investigated whether actin dynamics were implicated in regulating PCD. Using the actin-stabilizing and depolymerizing drugs jasplakinolide (Jasp) and latrunculin B, we demonstrate that changes in actin filament levels or dynamics play a functional role in initiating PCD in P. rhoeas pollen, triggering a caspase-3–like activity. Significantly, SI-induced PCD in incompatible pollen was alleviated by pretreatment with Jasp. This represents the first account of a specific causal link between actin polymerization status and initiation of PCD in a plant cell and significantly advances our understanding of the mechanisms involved in SI.

[Regulatory role of elements in the formation and accumulation of alkaloids in Papaver somniferum L. seedlings]

The effects of 12 elements on the formation and accumulation of isoquinolines were studied in opium poppy seedlings (Papaver somniferum L.). Three types of concentration dependences of the effects of the elements under study were determined. The elements served as activators (Co, Mo, W, Cr, and Cu) or inhibitors of these processes (B, Fe, V, Mn, and Ca). The molecular mechanisms of action of these regulators are discussed. The optimum concentrations of Co and Mo were tested under combined treatment conditions with these elements.

Virus-induced gene silencing is an effective tool for assaying gene function in the basal eudicot species Papaver somniferum (opium poppy)

Virus-induced gene silencing (VIGS) is an attractive method for assaying gene function in species that are resistant to conventional genetic approaches. However, VIGS has been shown to be effective in only a few, closely related plant species. Tobacco rattle virus (TRV), a bipartite RNA virus, has a wide host range and so in principle could serve as an efficient vector for VIGS in a diverse array of plant species. Here we show that a vector based on TRV sequences is effective at silencing the endogenous phytoene desaturase (PapsPDS) gene in Papaver somniferum (opium poppy). We show that this vector does not compromise the growth or reproduction of poppy and the plants did not display viral symptoms. The silencing of PapsPDS resulted in a significant reduction in PapsPDS mRNA and a concomitant photobleached phenotype. The ability to rapidly assay gene function in P. somniferum will be valuable in manipulation of the opiate pathway in this pharmaceutically important species. We suggest that our vacuum infiltration method used to deliver TRV-based vectors into poppy is a promising approach for expanding VIGS to diverse angiosperm species in which traditional delivery methods fail to induce VIGS. Furthermore, these studies demonstrate the utility of TRV-VIGS for probing gene function in a basal eudicot species that is phylogenetically distant from model plant species.

Comparative macroarray analysis of morphine containing Papaver somniferum and eight morphine free Papaver species identifies an O-methyltransferase involved in benzylisoquinoline biosynthesis

Benzylisoquinoline alkaloids constitute a group of about 2,500 structures and are mainly produced by plants of the order Ranunculales. But only the opium poppy, Papaver somniferum, and Papaver setigerum are able to produce morphine. In this study, we started to investigate by gene expression analysis the molecular basis for this exceptional biosynthetic ability. A sequencing project from P. somniferum seedlings was initiated using a method based on the amplified fragment length polymorphism technique that resulted in 849 UniGenes. These cDNAs were analysed on macroarrays for differential expression between morphine-containing P. somniferum plants and eight other Papaver species, which accumulate other benzylisoquinolines instead of morphine. Three cDNAs showing increased expression in P. somniferum compared to all the other Papaver species were identified. Whereas two showed no significant homology to any known protein, one putatively encoded an O-methyltransferase. Analysis of substrate specificity of the heterologously expressed protein and mass spectrometric identification of the enzymatic products identified this protein as S-adenosyl-L-methionine:(R,S)-3'-hydroxy-N-methylcoclaurine 4'-O-methyltransferase (EC 2.1.1.116). Unlike other O-methyltransferases of different positional specificities implicated in benzylisoquinoline metabolism, the enzyme only accepted tetrahydroxylated tetrahydrobenzylisoquinolines as substrates; methylation was tolerated only at the 6-hydroxy position.

Silencing nature's narcotics: metabolic engineering of the opium poppy

The opium poppy, Papaver somniferum L., and its narcotic and analgesic alkaloids, have an ancient history of use (and abuse) by humankind. A recent article by Allen and co-workers describes the metabolic engineering of morphine biosynthesis to block morphine formation and accumulate a potentially valuable pathway intermediate, (S)-reticuline. This work highlights the potential for modifying the production of pharmaceuticals in plants, but also raises questions about the complex regulation of biosynthetic pathways.

[Progress in study on signal transduction of gametophytic self-incompatibility]

In nature, most self-incompatible flowering plants (angiosperms) show gametophytic self-incompatibility. Although gametophytic self-incompatibility functions can ultimately prevent self-fertilization, flowering plants have adopted different signal transduction pathways to reject self pollen. At present, there are mainly two pathways of signal transduction on gametophytic self-incompatibility. One is the S-RNase-based signal transduction in Solanaceae, Scrophulariaceae, and Rosaceae. The other is the cytosolic free Ca2+ acting as a second messenger in pollen of Papaveraceae. This review highlights the recent progress made towards understanding the signal transduction on gametophytic self-incompatibility.

Sanguinarine biosynthesis is associated with the endoplasmic reticulum in cultured opium poppy cells after elicitor treatment

Three key benzylisoquinoline alkaloid biosynthetic enzymes, (S)-N-methylcoclaurine-3'-hydroxylase (CYP80B1), berberine bridge enzyme (BBE), and codeinone reductase (COR), were localized in cultured opium poppy (Papaver somniferum) cells by sucrose density gradient fractionation and immunogold labeling. CYP80B1 catalyzes the second to last step in the formation of (S)-reticuline, the last common intermediate in sanguinarine and morphine biosynthesis. BBE converts (S)-reticuline to (S)-scoulerine as the first committed step in sanguinarine biosynthesis, and COR catalyzes the penultimate step in the branch pathway leading to morphine. Sanguinarine is an antimicrobial alkaloid that accumulates in the vacuoles of cultured opium poppy cells in response to elicitor treatment, whereas the narcotic analgesic morphine, which is abundant in opium poppy plants, is not produced in cultured cells. CYP80B1 and BBE were rapidly induced to high levels in response to elicitor treatment. By contrast, COR levels were constitutive in the cell cultures, but remained low and were not induced by addition of the elicitor. Western blots performed on protein homogenates from elicitor-treated cells fractionated on a sucrose density gradient showed the cosedimentation of CYP80B1, BBE, and sanguinarine with calreticulin, and COR with glutathione S-transferase. Calreticulin and glutathione S-transferase are markers for the endoplasmic reticulum (ER) and the cytosol, respectively. In response to elicitor treatment, large dilated vesicles rapidly developed from the lamellar ER of control cells and fused with the central vacuole. Immunogold localization supported the association of CYP80B1 and BBE with ER vesicles, and COR with the cytosol in elicitor-treated cells. Our results show that benzylisoquinoline biosynthesis and transport to the vacuole are associated with the ER, which undergoes major ultrastructural modification in response to the elicitor treatment of cultured opium poppy cells.

RNAi-mediated replacement of morphine with the nonnarcotic alkaloid reticuline in opium poppy

We report on the silencing of codeinone reductase (COR) in the opium poppy, Papaver somniferum, using a chimeric hairpin RNA construct designed to silence all members of the multigene COR family through RNA interference (RNAi). After gene silencing, the precursor alkaloid (S)-reticuline-seven enzymatic steps upstream of codeinone-accumulated in transgenic plants at the expense of morphine, codeine, oripavine and thebaine. Methylated derivatives of reticuline also accumulated. Analysis verified loss of Cor gene transcript, appearance of 22-mer degradation products and reduction of enzyme activity. The surprising accumulation of (S)-reticuline suggests a feedback mechanism preventing intermediates from general benzylisoquinoline synthesis entering the morphine-specific branch. However transcript levels for seven other enzymes in the pathway, both before and after (S)-reticuline, were unaffected. This is the first report of gene silencing in transgenic opium poppy and of metabolic engineering to cause the high-yield accumulation of the nonnarcotic alkaloid reticuline.

Analgesia: morphine-pathway block in top1 poppies

The opium poppy is a source of the pharmaceuticals codeine, morphine and their derived analgesics. Here we describe the initial characterization of the poppy mutant known as top1 (for 'thebaine oripavine poppy 1'), which accumulates the morphine and codeine precursors thebaine and oripavine and does not complete their biosynthesis into morphine and codeine. The original discovery of top1 stimulated a re-engineering of the opioid industry in the island state of Tasmania, which grows over 40% of the world's licit opiates, in order to produce thebaine and oripavine efficiently from morphine-free poppy crops to provide precursors for highly effective analgesics and for treatment of opioid addiction.

The roles of latex and the vascular bundle in morphine biosynthesis in the opium poppy, Papaver somniferum

The opium poppy, Papaver somniferum, is one of mankind's oldest medicinal plants. Opium poppy today is the commercial source of the narcotic analgesics morphine and codeine. Along with these two morphinans, opium poppy produces approximately eighty alkaloids belonging to various tetrahydrobenzylisoquinoline-derived classes. It has been known for over a century that morphinan alkaloids accumulate in the latex of opium poppy. With identification of many of the enzymes of alkaloid biosynthesis in this plant, biochemical data suggested involvement of multiple cell types in alkaloid biosynthesis in poppy. Herein the immunolocalization of five enzymes of alkaloid formation in opium poppy is reported: (R,S)-3'-hydroxy-N-methylcoclaurine 4'-O-methyltransferase central to the biosynthesis of tetrahydroisoquinoline-derived alkaloids, the berberine bridge enzyme of the sanguinarine pathway, (R,S)-reticuline 7-O-methyltransferase specific to laudanosine formation, and salutaridinol 7-O-acetyltransferase and codeinone reductase, which lead to morphine. In capsule and stem, both O-methyltransferases and the O-acetyltransferase are found predominantly in parenchyma cells within the vascular bundle, and codeinone reductase is localized to laticifers, the site of morphinan alkaloid accumulation. In developing root tip, both O-methyltransferases and the O-acetyltransferase are found in the pericycle of the stele, and the berberine bridge enzyme is localized to parenchyma cells of the root cortex. Laticifers are not found in developing root tip, and, likewise, codeinone reductase was not detected. These results provide cell-specific localization that gives a coherent picture of the spatial distribution of alkaloid biosynthesis in opium poppy.

[Biosynthesis of poppy isoquinoline alkaloids in nature and in vitro culture. 2. Bracteum poppy (Papaver bracteatum Lindl.)]

Literature data and the data of the author's investigations on production of isoquinoline alkaloids by Papaver bracteatum Lindl. have been analyzed. Information on the methods of regulation and cell localization of morphine and sanguinarine biosynthesis is presented. The works studying differentiation processes in tissue cultures of bracteum poppy and relationship thereof with thebaine biosynthesis have been analyzed. Possible mechanism determining the induction of somatic embryos development and thebaine biosynthesis in the culture in vitro are proposed.

Cytomechanical properties of papaver pollen tubes are altered after self-incompatibility challenge

Self-incompatibility (SI) in Papaver rhoeas triggers a ligand-mediated signal transduction cascade, resulting in the inhibition of incompatible pollen tube growth. Using a cytomechanical approach we have demonstrated that dramatic changes to the mechanical properties of incompatible pollen tubes are stimulated by SI induction. Microindentation revealed that SI resulted in a reduction of cellular stiffness and an increase in cytoplasmic viscosity. Whereas the former cellular response is likely to be the result of a drop in cellular turgor, we hypothesize that the latter is caused by as yet unidentified cross-linking events. F-actin rearrangements, a characteristic phenomenon for SI challenge in Papaver, displayed a spatiotemporal gradient along the pollen tube; this suggests that signal propagation occurs in a basipetal direction. However, unexpectedly, local application of SI inducing S-protein did not reveal any evidence for localized signal perception in the apical or subapical regions of the pollen tube. To our knowledge this represents the first mechanospatial approach to study signal propagation and cellular responses in a well-characterized plant cell system. Our data provide the first evidence for mechanical changes induced in the cytoplasm of a plant cell stimulated by a defined ligand.

Hairy root induction of Papaver somniferum var. album, a difficult-to-transform plant, by A rhizogenes LBA 9402

Two strains of Agrobacterium rhizogenes (15834, LBA 9402) and one Agrobacterium tumefaciens strain [GV 3101 (PMP90RK, p35SGUS-2)] and four culture media were tested and compared for their ability to induce hairy root formation on wounded Papaver somniferum L. hypocotyls. Five weeks after the infection with A. rhizogenes LBA 9402, hairy roots appeared on 80% of the hypocotyls maintained in the hormone-free liquid medium. Six hairy-root cultures were established. Transformation was confirmed by polymerase chain reaction analysis. One clone was analysed for its alkaloid production. The total alkaloid content was higher in the transformed roots (0.46+/-0.06% DW) than in the untransformed roots (0.32+/-0.05% DW). The transformed roots accumulated three times more codeine (0.18+/-0.02% DW) than intact roots (0.05+/-0% DW). Moreover, morphine (0.255+/-0.03% DW) and sanguinarine (0.014+/-0% DW) were found in the liquid culture medium.

[Variability of flavonol contents during floral morphogenesis in Papaver somniferum L]

We studied the contents of flavonols (kaempferol and quercetin) in the meristem of vegetative and generative apices of the main plant shoot in floral Papaver somniferum mutants, as well as in the normal plants at successive stages of flower development. Five stages of flower development were distinguished. Flavonols (kaempferol and quercetin) were present in all flower organs at all stages of floral morphogenesis we studied. However, their contents and distribution in different organs and at different stages of flower development markedly varied. No significant differences were found in the contents of flavonols in the meristems of vegetative and generative apices of the main shoot in the lines of floral mutants, as well as between the lines with different amounts of vegetative phytomeres. In the plants with normal flower structure, the contents of flavonols (kaempferol + quercetin) sharply increased with the beginning of differentiation of flower organs, i.e. from stage 3, to reach a maximum in the open flower, when gametogenesis is terminated and fertilization takes place. The level of flavonol contents in the petals (upper part) and stamen was at a maximum at all stages of flower development, while that in the gynaecium was at a minimum. The kaempferol: quercetin ratio shifted towards quercetin at successive stages of flower development, most significantly in the stamens. The involvement of flavonols in the regulation of floral morphogenesis at stages of flower organs differentiation and functioning is discussed.

A tale of three cell types: alkaloid biosynthesis is localized to sieve elements in opium poppy

Opium poppy produces a diverse array of pharmaceutical alkaloids, including the narcotic analgesics morphine and codeine. The benzylisoquinoline alkaloids of opium poppy accumulate in the cytoplasm, or latex, of specialized laticifers that accompany vascular tissues throughout the plant. However, immunofluorescence labeling using affinity-purified antibodies showed that three key enzymes, (S)-N-methylcoclaurine 3'-hydroxylase (CYP80B1), berberine bridge enzyme (BBE), and codeinone reductase (COR), involved in the biosynthesis of morphine and the related antimicrobial alkaloid sanguinarine, are restricted to the parietal region of sieve elements adjacent or proximal to laticifers. The localization of laticifers was demonstrated using antibodies specific to the major latex protein (MLP), which is characteristic of the cell type. In situ hybridization showed that CYP80B1, BBE, and COR gene transcripts were found in the companion cell paired with each sieve element, whereas MLP transcripts were restricted to laticifers. The biosynthesis and accumulation of alkaloids in opium poppy involves cell types not implicated previously in plant secondary metabolism and dramatically extends the function of sieve elements beyond the transport of solutes and information macromolecules in plants.

Developmental and inducible accumulation of gene transcripts involved in alkaloid biosynthesis in opium poppy

Opium poppy (Papaver somniferum) produces a large number of benzylisoquinoline alkaloids, including morphine and sanguinarine, derived from tyrosine via the branch-point intermediate (S)-reticuline. Molecular clones for the three methlytransferases involved in (S)-reticuline biosynthesis, (S)-norcoclaurine-6-O-methyltransferase (6OMT), (S)-3'-hydroxy-N-methylcoclaurine-4'-O-methyltransferase (4'OMT), and (S)-coclaurine N-methyltransferase (CNMT), were isolated from opium poppy and shown to share extensive homology with the corresponding cDNAs from Japanese goldthread (Coptis japonica). These cDNAs were used together with previously isolated clones for tyrosine/dopa decarboxylase (TYDC), (S)-N-methylcoclaurine-3'-hydroxylase (CYP80B1), berberine bridge enzyme, (BBE), (7S)-salutaridinol 7-O-acetyltransferase (SAT), and codeinone reductase (COR), to compare the accumulation of gene transcripts encoding eight alkaloid biosynthetic enzymes in opium poppy. Transcript levels generally increased in developing seedlings and were consistently high in stems and flower buds, but were more variable in roots and leaves of mature plants. The accumulation of each transcript, with the exception of COR, showed a marked induction in response to elicitor treatment or wounding of cultured cells. Specific gene transcript levels often correlated with the accumulation of morphine or sanguinarine, with notable exceptions. Our data suggest some degree of coordination in the developmental and inducible regulation of alkaloid biosynthetic genes in opium poppy.

[Biosynthesis of poppy isoquinoline alkaloids in nature and in vitro culture. 1. Opium poppy (Papaver somniferum L.)]

The analysis of literature data on production of isoquinoline alkaloids by Papaver somniferum L. plants and cell cultures has been made. The relationship of morphinane alkaloids biosynthesis with the processes of tissue and cell differentiation are discussed. The information on enzymes and pathways of regulation of morphine and sanguinarine biosynthesis are presented. The data on sanguinarine and morphine physiological role are analyzed.

[Study of degradation of flavonols in the mutants of poppy (Papaver somniferum L.)]

We studied flavonol-degrading activity of cell-free extracts from petals of the flower color and structure mutants. The relationship between degradation of flavonols (kaempferol, quercetin, and myricetin) and biosynthesis of anthocyanins has been revealed. The highest flavonol-degrading activity has been revealed in white flower mutants towards all substrates, particularly, quercetin. The mutations inhibiting synthesis of an anthocyanin pelargonidin provide for synthesis of various quantities of cyanidin in the petals. The flavonol-degrading activity considerably increases with the content of cyanidin. A similar relationship has been revealed in the mutants synthesizing both cyanidin and pelargonidin. The plants accumulating considerable quantities of pelargonidin in their petals have accordingly higher flavonol-degrading activity and predominantly hydrolyze kaempferol. The plants forming additional pods in their flower (pistillody) have higher flavonol-degrading activity as compared to the anther-in-petal and doubleness mutants.

Modulation of berberine bridge enzyme levels in transgenic root cultures of California poppy alters the accumulation of benzophenanthridine alkaloids

California poppy (Eschscholzia californica Cham.) root cultures produce a variety of benzophenanthridine alkaloids, such as sanguinarine, chelirubine and macarpine, with potent biological activity. Sense and antisense constructs of genes encoding the berberine bridge enzyme (BBE) were introduced into California poppy root cultures. Transgenic roots expressing BBE from opium poppy (Papaver somniferum L.) displayed higher levels of BBE mRNA, protein and enzyme activity, and increased accumulation of benzophenanthridine alkaloids compared to control roots transformed with a beta-glucuronidase gene. In contrast, roots transformed with an antisense-BBE construct from California poppy had lower levels of BBE mRNA and enzyme activity, and reduced benzophenanthridine alkaloid accumulation, relative to controls. Pathway intermediates were not detected in any transgenic root lines. Suppression of benzophenanthridine alkaloid biosynthesis using antisense-BBE also reduced the growth rate of the root cultures. Two-dimensional 1H-NMR spectroscopy showed no difference in the abundance of carbohydrate metabolites in the various transgenic roots lines. However, transformed roots with low levels of benzophenanthridine alkaloids contained larger cellular pools of certain amino acids compared to controls. In contrast, cellular pools of several amino acids were reduced in transgenic roots with elevated benzophenanthridine alkaloid levels relative to controls. The relative abundance of tyrosine, from which benzophenanthridine alkaloids are derived, was only marginally altered in all transgenic root lines; thus, altering metabolic flux through benzophenanthridine alkaloid pathways can affect cellular pools of specific amino acids. Consideration of such interactions is important for the design of metabolic engineering strategies that target benzophenanthridine alkaloid biosynthesis.

The actin cytoskeleton is a target of the self-incompatibility response in Papaver rhoeas

The integration of signals received by a cell, and their transduction to targets, is essential for all cellular responses. The cytoskeleton has been identified as a major target of signalling cascades in both animal and plant cells. Self-incompatibility (SI) in Papaver rhoeas involves an allele-specific recognition between stigmatic S-proteins and pollen, resulting in the inhibition of incompatible pollen. This highly specific response triggers a Ca(2+)-dependent signalling cascade in incompatible pollen when a stigmatic S-protein interacts with it. It has been demonstrated recently that SI induces dramatic alterations in the organization of the pollen actin cytoskeleton. This implicates the actin cytoskeleton as a key target for the SI-stimulated signals. The cytological alterations to the actin cytoskeleton that are triggered in response to SI are described here and there seem to be several stages that are distinguishable temporally. Evidence was obtained that F-actin depolymerization is also stimulated. The current understanding that the actin cytoskeleton is a target for the signals triggered by the SI response is discussed. It is suggested that these F-actin alterations may be Ca(2+)-mediated and that this could be a mechanism whereby SI-induced tip growth inhibition is achieved. The potential for actin-binding proteins to act as key mediators of this response is discussed and the mechanisms that may be responsible for effecting these changes are described. In particular, the parallels between sustained actin rearrangements during SI and in apoptosis of animal cells are considered.

Immunocytological localization of two enzymes involved in berberine biosynthesis

Using post-embedding immunogold techniques the cytological localization of the two branchpoint enzymes of isoquinoline biosynthesis, berberine bridge enzyme (BBE) and (S)-tetrahydroprotoberberine oxidase (STOX), was demonstrated. Electron-microscopic examination revealed their exclusive compartmentation within vesicles. After these vesicles have fused with the central vacuole, they release their contents, resulting in a characteristic electron-dense precipitate at the tonoplast. Vesicles of similar structure could be identified in young meristematic tissues of roots or shoots from different Berberis species and Papaver somniferum L. The appearance of electron-dense osmiophilic material is strictly correlated with the alkaloid content of the tissue. Immunocytological staining of P. somniferum tissue with antibodies directed against BBE led to a characteristic labeling of electron-dense aggregates in idioblasts that are not connected to the laticifer system. This localization demonstrates the strictly cytological separation of benzophenanthridine and morphine biosyntheses within this plant.

Signal-mediated depolymerization of actin in pollen during the self-incompatibility response

Signal perception and the integration of signals into networks that effect cellular changes is essential for all cells. The self-incompatibility (SI) response in field poppy pollen triggers a Ca(2+)-dependent signaling cascade that results in the inhibition of incompatible pollen. SI also stimulates dramatic alterations in the actin cytoskeleton. By measuring the amount of filamentous (F-) actin in pollen before and during the SI response, we demonstrate that SI stimulates a rapid and large reduction in F-actin level that is sustained for at least 1 h. This represents quantitative evidence for stimulus-mediated depolymerization of F-actin in plant cells by a defined biological stimulus. Surprisingly, there are remarkably few examples of sustained reductions in F-actin levels stimulated by a biologically relevant ligand. Actin depolymerization also was achieved in pollen by treatments that increase cytosolic free Ca(2+) artificially, providing evidence that actin is a target for the Ca(2+) signals triggered by the SI response. By determining the cellular concentrations and binding constants for native profilin from poppy pollen, we show that profilin has Ca(2+)-dependent monomeric actin-sequestering activity. Although profilin is likely to contribute to stimulus-mediated actin depolymerization, our data suggest a role for additional actin binding proteins. We propose that Ca(2+)-mediated depolymerization of F-actin may be a mechanism whereby SI-induced tip growth inhibition is achieved.

[Effect of a fungal elicitor on levels of sanguinarine and polyphenoloxidase activity in a suspension culture of Papaver somniferum L]

The opium poppy (Papaver somniferum L.) is still a source for isolation of codeine and morphine. Cell cultures from this plant lose their ability to produce morphinans. Their major alkaloid is sanguinarine. The elicitation of the opium poppy cell cultures by fungal preparation lead to a nine-fold increase in the content of sanguinarine. The specific activity of polyphenoloxidase (PPO) was three-times higher in the elicited compared to the nonelicited cells. Two isoforms of PPO (Mr 63 kDa, 41 kDa) were identified in opium poppy cell cultures by PAGE. The number of PPO isoforms was not affected by elicitation. Phenyl-Sepharose CL-4B was used for affinity purification of PPO. In a single purification step the specific activity of PPO was enriched 14-fold.

Morphine, the Proteus of organic molecules

This feature article encapsulates the senior author's longstanding interests in opiate chemistry and attempts to place it within an historical context and against the backdrop of related work by others who have viewed morphine as one of the pinnacles of natural product synthesis. Biomimetic and 'bioanalogous' routes to the morphine skeleton are discussed followed by approaches based on the elaboration of phenanthrene platforms. The latter include an asymmetric synthesis of ent-morphine developed in our laboratory.

Isoquinoline alkaloid production by transformed cultures of Papaver somniferum

Three clones of transformed cultures of opium poppy (Papaver somniferum L.) were established by infection with Agrobacterium rhizogenes MAFF 03-01724. MAFF clone 1 being capable of forming somatic embryos was selected and its growth and isoquinoline alkaloid production was investigated. The illumination, temperature and nutrient medium composition greatly affected growth, cell morphology and alkaloid accumulation. The MAFF clone 1 cultured in Root Culture medium in the dark at 22 degrees C accumulated a high quantity of sanguinarine (652 micrograms/g dry weight) though the growth was poor (4.4 fold as fresh weight basis after 2 months of culture). The MAFF clone 1 cultured in a quarter macro salt strength Woody Plant medium under 14 h/day light at 22 degrees C developed into plantlets and accumulated significant quantity of codeine (648 micrograms/g dry wt) together with papaverine, noscapine, and sanguinarine. This clone was applied to a rotating drum fermenter (2 L working volume), and ca. 0.3 mg codeine and 0.06 mg sanguinarine were obtained after 4 weeks of culture. One quarter of the codeine produced was found in the culture medium.

Morphine metabolism in the opium poppy and its possible physiological function. Biochemical characterization of the morphine metabolite, bismorphine

We identified a novel metabolic system of morphine in the opium poppy (Papaver somniferum L.). In response to stress, morphine is quickly metabolized to bismorphine consisting of two morphine units, followed by accumulation in the cell wall. This bismorphine binds predominantly to pectins, which possess high galacturonic acid residue contents, through ionical bonds. Our newly developed method using artificial polysaccharides demonstrated that bismorphine bridges are formed between the two amino groups of bismorphine and the carboxyl groups of galacturonic acid residues, resulting in cross-linking of galacturonic acid-containing polysaccharides to each other. The ability of bismorphine to cross-link pectins is much higher than that of Ca2+, which also acts as a cross-linker of these polysaccharides. Furthermore, we confirmed that cross-linking of pectins through bismorphine bridges leads to resistance against hydrolysis by pectinases. These results indicated that production of bismorphine is a defense response of the opium poppy. Bismorphine formation is catalyzed by anionic peroxidase that pre-exists in the capsules and leaves of opium poppies. The constitutive presence of morphine, together with bismorphine-forming peroxidase, enables the opium poppy to rapidly induce the defense system.

Berberine bridge enzyme, a key branch-point enzyme in benzylisoquinoline alkaloid biosynthesis, contains a vacuolar sorting determinant

In opium poppy (Papaver somniferum L.), (S)-reticuline is the last common intermediate in sanguinarine and morphine biosynthesis. Sanguinarine accumulates in the vacuole of cultured opium poppy cells in response to treatment with fungal elicitors. The first committed step in sanguinarine biosynthesis is catalyzed by the berberine bridge enzyme (BBE), which converts (S)-reticuline to (S)-scoulerine. An N-terminal signal peptide and novel vacuolar sorting determinant were identified and characterized in BBE. In vitro translation of BBE mRNA in the presence of canine pancreatic microsomes produced a glycosylated, proteolysis-resistant protein, confirming the existence of a signal peptide. Transcripts encoding a BBE N-terminal deletion series fused to beta-glucuronidase or green fluorescent protein (GFP) were also translated in the presence of canine microsomes, and introduced into cultured opium poppy cells via microprojectile bombardment. The signal peptide was restricted to the first 25 amino acids and shown to initially target BBE to the endoplasmic reticulum. Fusion of 50 N-terminal residues from BBE to GFP resulted in the localization of the reporter to the vacuole. GFP was also sorted to the vacuole when fused to a heterologous N-terminal signal peptide followed by BBE amino acids 26-50. The BBE vacuolar sorting determinant was further localized between residues 26 and 41 by deletion analysis. The final subcellular destination of BBE is consistent with the vacuolar sequestration of sanguinarine. However, the vacuolar pH is below the functional range for BBE, suggesting that the enzyme is active only prior to its entry into the vacuole.

Isolation and partial characterization of norcoclaurine synthase, the first committed step in benzylisoquinoline alkaloid biosynthesis, from opium poppy

Norcoclaurine synthase (NCS) catalyzes the condensation of dopamine and 4-hydroxyphenylacetaldehyde (4-HPAA) to yield norcoclaurine, the common precursor to all benzylisoquinoline alkaloids produced in plants. In opium poppy (Papaver somniferum L.), NCS activity was detected in germinating seeds, young seedlings, and all mature plant organs, especially stems and roots. However, the highest levels of activity were found in cell-suspension cultures treated with a fungal elicitor. NCS activity was induced more than 20-fold over an 80-h period in response to elicitor treatment. Compared to opium poppy. basal NCS activity was 3-and 5-fold higher in benzylisoquinoline alkaloid-producing cell cultures of Eschscholzia californica and Thalictrum flavum ssp. glaucum, respectively. In contrast, NCS activity was not detected in cultured cells of Nicotiana tabacum and Catharanthus roseus, which do not produce benzylisoquinoline alkaloids. NCS displayed maximum activity between pH 6.5 and 7.0, and a broad temperature optimum between 42 and 55 degrees C. Enzyme activity was not affected by Ca2+ or Mg2+, and was not inhibited by a variety of benzylisoquinoline alkaloids. NCS showed hyperbolic saturation kinetics for 4-HPAA, with an apparent Km of 1.0 mM. However, the enzyme exhibited sigmoidal saturation kinetics for dopamine with a Hill coefficient of 1.84. NCS enzymes from E. californica and T. flavum displayed similar properties. These data indicate that NCS exhibits positive cooperativity between substrate-binding sites. Enzymes of this type catalyze regulatory, or rate-limiting, steps in metabolism, suggesting that NCS plays a role in controlling the rate of pathway flux in benzylisoquinoline alkaloid biosynthesis.

[Magnetic liquid influence upon some plant species of pharmaceutical interest]

It was accomplished a study on the influence of a petroleum magnetic liquid upon two plant species of pharmaceutical interest: Papaver somniferum L. and Chelidonium majus L. Experimental observation aimed: callus accumulation, seed germination, mitotic index and fluorescence of the photosynthesis pigments. The plant samples were taken from in vitro cultures obtained from different explant types while the magnetic liquid was added in the culture media in low concentrations (ml/l). The germination test showed a positive influence of the magnetic liquid, the cell division test revealed an increased mitotic index, callus accumulation rate is enhanced while the fluorescence spectra showed maxima shift for the samples in comparison to the controls.

Alkaloid biosynthesis in Papaver sp. cells in culture and during organogenesis

In vitro cell cultures of two Papaver species, P. somniferum and P. bracteatum initiated from mature seeds were screened for their ability to produce alkaloids. Protocols for callus induction, somatic embryogenesis and organogenesis were established. The alkaloid contents were analysed by high-performance-liquid chromatography, thin-layer chromatography and spectrophotometric assays. Undifferentiated callus produced small amounts of sanguinarine, which increased with the degree of tissue differentiation. Embryogenic calli were maintained in culture for more than 2 years, retaining a high regeneration capability. Thin-layer chromatography analysis revealed variations in alkaloid spectrum between parallel cell lines. The morphinan alkaloid, thebaine, was found to be accumulated exclusively in morphogenous strains of P. bracteatum, and morphine was the major alkaloid in the spectrum of P. somniferum dedifferentiated callus. Regenerant plants synthesized thebaine and sanguinarine at the same level as juvenile plants grown from P. bracteatum seeds. We revealed differences in the ability to produce different types of alkaloids: seed-derived plants were able to accumulate thebaine while undifferentiated primary cell cultures produced only sanguinarine. The production of either sanguinarine and morphinan alkaloids are found in regenerants showing that both metabolic pathways were active in young plantlets.

Evidence for DNA fragmentation triggered in the self-incompatibility response in pollen of Papaver rhoeas

Studies of the molecular and biochemical basis of self-incompatibility (SI) in Papaver rhoeas have revealed much about the signalling pathways triggered in pollen early in this response. The aim of the current investigation was to begin to study downstream events in order to elucidate some of the later cellular responses involved in the SI response and identification of the mechanisms controlling the irreversible inhibition of pollen tube growth. We have used the FragEL assay to investigate if there is any evidence for DNA fragmentation stimulated in pollen of P. rhoeas in an S-specific manner. Our data clearly demonstrate that S proteins are responsible for triggering this, specifically in incompatible, and not compatible, pollen. DNA fragmentation was first detected in incompatible pollen tubes 4 h after challenge with S proteins, and continued to increase for a further 10 h. This provides the first evidence, to our knowledge, that this phenomenon is associated with the SI response. We also demonstrate that mastoparan, which increases [Ca2+]i, also triggers DNA fragmentation in these pollen tubes, thereby implicating an involvement of Ca2+ signalling in this process. Together, our data represent a significant breakthrough in understanding of the SI response in Papaver pollen.

Structure-activity relationships of synthetic analogs of jasmonic acid and coronatine on induction of benzo[c]phenanthridine alkaloid accumulation in Eschscholzia californica cell cultures

A facile test system based on the accumulation of benzo[c]phenanthridine alkaloids in Eschscholzia californica cell suspension culture (an indicator of defense gene activation) has been used to analyze a series of synthetic compounds for elicitor-like activity. Of the 200 jasmonic acid and coronatine analogs tested with this system, representative results obtained with 49 of them are presented here. The following can be summarized concerning structure-activity relationships: there is a large degree of plasticity allowed at the C-3 of jasmonic acid in the activation of defense genes. The carbonyl moiety is not strictly required, but exocyclic double bond character appears necessary. The pentenyl side chain at C-2 cannot tolerate bulky groups at the terminal carbon and still be biologically active. Substitutions to the C-1' position are tolerated if they can potentially undergo beta-oxidation. Either an alkanoic acid or methyl ester is required at C-1, or a side chain that can be shortened by beta-oxidation or by peptidase hydrolysis. Coronatine and various derivatives thereof are not as effective as jasmonic acid, and derivatives in inducing benzo[c]phenanthridine alkaloid accumulation. Jasmonic acid rather than the octadecanoic precursors is therefore considered to be a likely signal transducer of defense gene activation in planta.

Alterations in the actin cytoskeleton of pollen tubes are induced by the self-incompatibility reaction in Papaver rhoeas

Self-incompatibility (SI) is a genetically controlled process used to prevent self-pollination. In Papaver rhoeas, the induction of SI is triggered by a Ca(2)+-dependent signaling pathway that results in the rapid and S allele-specific inhibition of pollen tube tip growth. Tip growth of cells is dependent on a functioning actin cytoskeleton. We have investigated the effect of self-incompatibility (S) proteins on the actin cytoskeleton in poppy pollen tubes. Here, we report that the actin cytoskeleton of incompatible pollen tubes is rapidly and dramatically rearranged during the SI response, not only in our in vitro SI system but also in vivo. We demonstrate that nonspecific inhibition of growth does not result in similar actin rearrangements. Because the SI-induced alterations are not observed if growth stops, this clearly demonstrates that these alterations are triggered by the SI signaling cascade rather than merely resulting from the consequent inhibition of growth. We establish a detailed time course of events and discuss the mechanisms that might be involved. Our data strongly implicate a role for the actin cytoskeleton as a target for signaling pathways involved in the SI response of P. rhoeas.