Senecio spp.: Biochemistry of the Formation of Pyrrolizidine Alkaloids in Root Cultures

Hartmann, Thomas

doi:10.1007/978-3-642-57970-7_23

Cited by 18 publications

(16 citation statements)

References 37 publications

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“…To test the specificity of the resulting HSS-specific antibody, extracts of PA-producing root cultures of related Asteraceae species and an extract of the aerial root tips of the Orchidaceae Phalaenopsis sp. that were previously characterized as a site of PA biosynthesis (Bö ttcher et al, 1993;Hartmann, 1994; N. Nurhayati, S. Anke, C. Frö lich, and D. Ober, unpublished data) were separated and detected by immunoblot analysis (Fig. 2A).…”

Section: Antibody Preparation and Specificitymentioning

confidence: 99%

Polyphyletic Origin of Pyrrolizidine Alkaloids within the Asteraceae. Evidence from Differential Tissue Expression of Homospermidine Synthase

et al. 2004

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The evolution of pathways within plant secondary metabolism has been studied by using the pyrrolizidine alkaloids (PAs) as a model system. PAs are constitutively produced by plants as a defense against herbivores. The occurrence of PAs is restricted to certain unrelated families within the angiosperms. Homospermidine synthase (HSS), the first specific enzyme in the biosynthesis of the necine base moiety of PAs, was originally recruited from deoxyhypusine synthase, an enzyme involved in the posttranslational activation of the eukaryotic initiation factor 5A. Recently, this gene recruitment has been shown to have occurred several times independently within the angiosperms and even twice within the Asteraceae. Here, we demonstrate that, within these two PA-producing tribes of the Asteraceae, namely Senecioneae and Eupatorieae, HSS is expressed differently despite catalyzing the same step in PA biosynthesis. Within Eupatorium cannabinum, HSS is expressed uniformly in all cells of the root cortex parenchyma, but not within the endodermis and exodermis. Within Senecio vernalis, HSS expression has been previously identified in groups of specialized cells of the endodermis and the adjacent root cortex parenchyma. This expression pattern was confirmed for Senecio jacobaea as well. Furthermore, the expression of HSS in E. cannabinum is dependent on the development of the plant, suggesting a close linkage to plant growth.

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Section: Antibody Preparation and Specificitymentioning

confidence: 99%

Polyphyletic Origin of Pyrrolizidine Alkaloids within the Asteraceae. Evidence from Differential Tissue Expression of Homospermidine Synthase

et al. 2004

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“…The two tracers were obtained biosynthetically by feeding of [1,4-i4C]putrescine (109 mCi . mmol-' ; Amersham Buchler) to root cultures of Senecio vulgaris as described by Hartmann (1994).…”

Section: Preparation Of [14c]senecionine and ['4cmentioning

confidence: 99%

“…Retronecine and heliotridine were prepared by alkaline hydrolysis of monocrotaline and heliotrine, respectively . 14C-Labeled pyrrolizidine alkaloids were isolated from the respective root cultures after feeding of labeled putrescine as biosynthetic precursor (Hartmann, 1994 cerus. The results (Table 1) give two main answers: (a) exclusively ['4C]senecionine N-oxide could be detected in extracts of insects which had fed on either of the two alkaloidal forms; (b) there is no significant difference in the amount of sequestered alkaloid N-oxide between insects having fed on senecionine and senecionine N-oxide.…”

Section: Preparation Of Haemolymph and Alkaloid Analysismentioning

confidence: 99%

The two Faces of Pyrrolizidine Alkaloids: the Role of the Tertiary Amine and its N‐Oxide in Chemical Defense of Insects with Acquired Plant Alkaloids

Lindigkeit

Biller

Buch

et al. 1997

European Journal of Biochemistry

133

119

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Larvae of Creatonotos transiens (Lepidoptera, Arctiidae) and Zonocerus variegatus (Orthoptera, Pyrgomorphidae) ingest 14C-labeled senecionine and its N-oxide with the same efficiency but sequester the two tracers exclusively as N-oxide. Larvae of the non-sequestering Spodoptera littoralis eliminate efficiently the ingested alkaloids. During feeding on the two alkaloidal forms transient levels of senecionine (but not of the N-oxide) are built up in the haemolymph of S. littoralis larvae. Based on these results, senecionine [*80]N-o~ide was fed to C. transiens larvae and Z. variegatus adults. The senecionine Noxide recovered from the haemolymph of the two insects shows an almost complete loss of "0 label, indicating reduction of the orally fed N-oxide in the guts, uptake of the tertiary alkaloid and its re-N-oxidation in the haemolymph. The enzyme responsible for N-oxidation is a soluble mixed function monooxygenase. It was isolated from the haemolymph of the sequestering arctiid Tyria jacobaeue and purified to electrophoretic homogeneity. The enzyme is a flavoprotein with a native M , of 200000 and a subunit M , of 51 000. It shows a pH optimum at 7.0, has its maximal activity at a temperature of 40-45°C and an isoelectric point at pH 4.9. The reaction is strictly NADPH-dependent (K,,, 1.3 pM). From 20 pyrrolizidine alkaloids so far tested as substrates, the enyzme N-oxidizes only alkaloids with structural elements which are essential for hepatotoxic and genotoxic pyrrolizidine alkaloids (i.e. 1,2-double bond, esterification of the allylic hydroxyl group, presence of a second free or esterified hydroxyl group at carbon 7). A great variety of related alkaloids and xenobiotics were tested as substrate, none was accepted. The K, values of senecionine, monocrotaline and heliotrine, representing the three main types of pyrrolizidine alkaloids, are 1.3 pM, 12.5 pM and 290 pM, respectively. The novel enzyme was named senecionine N-oxygenase (SNO). The enzyme was partially purified from two other arctiids. The three SNOs show the same general substrate specificity but differ in their affinities towards the main structural types of pyrrolizidine alkaloids. The enzymes from the two generalists (Creatonotos transiens and Arctia caja) display a broader substrate affinity than the enzyme from the specialist (Tyria jacobaeae). The two molecular forms of pyrrolizidine alkaloids, the lipophilic protoxic tertiary amine and its hydrophilic nontoxic N-oxide are discussed in respect to their bioactivation and detoxification in mammals and their role as defensive chemicals in specialized insects. Pyrrolizidine-alkaloid-sequestering insects store the alkaloids as nontoxic N-oxides which are reduced in the guts of any potential insectivore. The lipophilic tertiary alkaloid is absorbed passively and then bioactivated by cytochrome P-450 oxidase.Keywords: Tyria jacobaeae (Lepidoptera, Arctiidae) ; pyrrolizidine alkaloid; alkaloid uptake; senecionine N-oxygenase ; chemical defense.Pyrrolizidine alkaloids are unique among the some 20 000 p...

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“…Opilionids are considered to be generalist predators. Predation of beetle larvae by opilionids is poorly documented (Drummoud et al 1990 (Hartmann 1994). Tracerlabeled diet was prepared by adding 80 µl of the aqueous tracer solution to 220 mg of thoroughly minced beef meat.…”

Section: Introductionmentioning

confidence: 99%

Detoxification of pyrrolizidine alkaloids by the harvestman Mitopus morio (Phalangidae) a predator of alkaloid defended leaf beetles

Hartmann

Häggström²,

Theuring

et al. 2003

Chemoecology

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Summary. The harvestman Mitopus morio (Phalangidae) is a generalist predator. It is known to prey on larvae of the chrysomelid leaf beetle Oreina cacaliae defended by plant acquired pyrrolizidine alkaloids (PAs). Tracer feeding experiments were performed to determine how harvestmen tolerate protoxic PAs. Minced meat containing either [ 14 C]senecionine or [ 14 C]senecionine N-oxide was fed to M. morio and subsequently feces and bodies were analyzed. Labeled alkaloid N-oxide remained stable and was eliminated almost unaltered with the feces; only 10% was recovered as tertiary PA. In contrast, approximately 80% of labeled tertiary alkaloid (senecionine) ingested with the diet was N-oxidized and eliminated; the remaining 20% consisted of unchanged senecionine and a polar metabolite of unknown structure. Harvestmen process their diet by excreting digestive juice, indicated by bleaching of the meat color. Analysis of the processed diet revealed some N-oxidation of [14 C]senecionine, suggesting the gut as the site of Noxidation. Analysis of the bodies of harvestmen 80 hours after the tracer feeding pulse revealed only trace amounts of the polar metabolite. Neither senecionine nor its N-oxide could be detected in the body extracts. The results are discussed in relation to the strategies of PA adapted insects to avoid accumulation of tertiary PAs in living tissues.

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Senecio spp.: Biochemistry of the Formation of Pyrrolizidine Alkaloids in Root Cultures

Cited by 18 publications

References 37 publications

Polyphyletic Origin of Pyrrolizidine Alkaloids within the Asteraceae. Evidence from Differential Tissue Expression of Homospermidine Synthase

Polyphyletic Origin of Pyrrolizidine Alkaloids within the Asteraceae. Evidence from Differential Tissue Expression of Homospermidine Synthase

The two Faces of Pyrrolizidine Alkaloids: the Role of the Tertiary Amine and its N‐Oxide in Chemical Defense of Insects with Acquired Plant Alkaloids

Detoxification of pyrrolizidine alkaloids by the harvestman Mitopus morio (Phalangidae) a predator of alkaloid defended leaf beetles

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