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21.
Summary. A widely distributed host race of Tyria jacobaeae lives on Senecio jacobaea and related species and accumulates pyrrolizidine alkaloids (“PA race”), another race, which is restricted to the Alps and
found on Petasites paradoxus, sequesters sesquiterpenes, such as petasol and isopetasol. Nucleotide sequences of the mitochondrial 16S rDNA gene show
1% sequence divergence, indicating that genetical differences exist between the PA exploiting and the terpene-sequestering
host races of T. jacobaeae. This finding suggests that both host races of T. jacobaeae must have been separated for some time already, possibly since the Pleistocene.
Received 2 May 2001; accepted 1 June 2001. 相似文献
22.
23.
Thomas Hartmann Claudine Theuring Till Beuerle Elizabeth A. Bernays 《Chemoecology》2004,14(3-4):207-216
Summary. The alkaloid profiles of the life history stages
of the highly polyphagous arctiid Estigmene acrea were
established. As larvae individuals had free choice between
a plain diet (alkaloid-free) and a diet that was supplemented
with Crotalaria-pumila powder with a known content and
composition of pyrrolizidine alkaloids (PAs). Idiosyncratic
retronecine esters (insect PAs) accounted for approximately
half of the PAs recovered from the larvae. These alkaloids
were synthesized by the larvae through esterification of dietary
supinidine yielding the estigmines, and esterification of
retronecine yielding the creatonotines. The retronecine is
derived from insect-mediated degradation of the sequestered
pumilines (macrocyclic PAs of the monocrotaline type).
With one exception, the PA profiles established for larvae
were found almost unaltered in all life-stages as well as
larval exuviae and pupal cocoons. The exception is the
males, which in comparison to pupae and adult females,
showed a significantly decreased quantity of the creatonotines
and pumilines. These data support the idea that
the creatonotines are direct precursors of the PA-derived male
courtship pheromone, hydroxydanaidal. Crosses of PA-free
males with PA-containing females and vice versa confirmed
an efficient trans-mission of PAs from males to females and
then from females to eggs. In single cases a male bestowed
almost his total PA load to the female, and a female her total load
to the eggs. The results are discussed with respect to pheromone
formation, PA transmission between life-stages, and the
defensive role of PAs against predators and parasitoids 相似文献
24.
Alkaloid tolerance in Manduca sexta and phylogenetically related sphingids (Lepidoptera: Sphingidae) 总被引:2,自引:0,他引:2
Summary. Nicotine tolerance is well known for Manduca sexta. It also occurs in several other sphingids of the subfamilies Macroglossinae and Sphinginae. Only members of the subfamily
Smerinthinae appear to be more susceptible to nicotine intoxication. Phylogenetic trees have been reconstructed from mitochondrial
16S rDNA and nuclear DNA to map nicotine tolerance.?The nicotine binding site of both α-subunits of nicotinic acetylcholine receptors (nAChR) have been amplified and sequenced. No apparent amino acid substitution
can be seen in the putative nicotine binding site of the α-subunits of nAChR from nicotine tolerant and nicotine sensitive sphingids. Thus, a simple target-site modification can be
ruled out as a cause for nicotine tolerance. This finding agrees with feeding experiments: larvae of M. sexta and other sphingids of the Macroglossinae and Sphinginae not only tolerated nicotine, but also many other alkaloids that
affect neuroreceptors other than acetylcholine receptors (nAChR, mAChR).?Only 10 to 20% of nicotine injected into larvae of
nicotine-tolerant taxa could be recovered later as free nicotine, nicotine N-oxide or cotinine, i.e., 80 to 90% must have been converted to polar conjugates or degradation products which are not detectable with the methods
applied. Usually more than 98% of the recoverable alkaloids were found in the faeces. Excretion reached a maximum 6 h after
injection in tolerant taxa. Larvae of Manduca sexta, which were reared on a nicotine-rich diet, showed higher nicotine degradation and faster nicotine elimination than na?ve
larvae. Application of the cytochrome P450 inhibitor SKF 525A (proadifen) reduced the formation of nicotine N-oxide and the rate of alkaloid degradation. Thus, an
inducible detoxification mechanism, coupled with a rapid and inducible excretion, appear to be a strategy in Sphingidae that
helps them to live on host plants rich in otherwise toxic secondary metabolites.
Received 23 March 2001; accepted 4 August 2001. 相似文献
25.
Juan Camilo Marín Loaiza Carlos L. Céspedes Till Beuerle Claudine Theuring Thomas Hartmann 《Chemoecology》2007,17(2):109-115
Summary. The occurrence of pyrrolizidine alkaloids (PAs) in Pittocaulon (ex Senecio) praecox (Asteraceae) a species endemic to Mexico was established. The aboveground plant organs contain the 1,2-saturated monoester
7-angeloyl-dihydroxyheliotridane together with a small proportion of its 9-angeloyl isomer as major alkaloid. The monoesters
are accompanied by the macrocyclic otonecine derivative senkirkine. Roots contain only related macrocyclic PAs with senecionine,
senkirkine and platyphylline as major components; monoesters are absent. The broom-like succulent stems of P. praecox are infested by the scale insect Ceroplastes albolineatus conspicuously visible by its huge wax cover. All life-history stages, i.e. females, eggs, first instar nymphs (crawlers)
and the wax cover were found associated with PAs. The measured PA concentrations clearly indicate sequestration. The highest
PA concentrations (mg / g dry weight) reached are: mature females, 0.44; eggs, 0.58; crawlers, 0.37; wax cover, 0.08. The
host plant as well as in the infesting scale insect contain the PAs exclusively as free bases. As a phloem-feeder C. albolineatus must acquire the PAs with the ingested phloem sap. This appears plausible since in Senecio species PA are transmitted and circulated through the phloem path. It is suggested that PAs may protect particularly the
crawlers as the most endangered stage in the life-cycle of the scale insect. 相似文献
26.
Summary. Hydroxydanaidal, the pyrrolizidine alkaloid-derived male corematal pheromone active in the close-range precopulatory interactions
of the moth Utetheisa ornatrix, appears not to contribute to the chemical defense of this moth. The compound failed to manifest feeding deterrency as an
additive to mealworms, in assays with a lycosid spider (Lycosa ceratiola). Moreover, contact with the male’s coremata, such as appears to occur inevitably in consequence of courtship in Utetheisa, does not in itself reduce the palatability of the female moth. 相似文献
27.
Summary. The ontogeny of pyrrolizidine alkaloid (PA) synthesis
and constraints on defence level during the seedling stage were examined
in the annual Senecio vulgaris and the monocarpic perennial
Senecio jacobaea. In both species, PAs were actively
synthesized from the onset of seedling growth so that juvenile stages
did not go through an undefended stage. Roots are known to be the
exclusive sites where PAs are produced. Root biomass was the single most
important biomass parameter explaining variation in total PAs per
seedling. All correlation coefficients between—relative growth
rate and PA concentration were negative, but none was significant.
However, a significant negative—correlation was found between
shoot to root ratio and PA concentration in S. jacobaeaseedlings, suggesting a dilution effect of the PAs. Earlier studies have
shown that the shoot to root ratio is positively correlated with
relative growth—rate of established S. jacobaea plants.
It is therefore suggested that young S. jacobaea plants
with a high shoot to root ratio and hence a high growth capacity
necessarily have lower PA defence levels than plants with a low
shoot to root ratio.
Received 10 July 2002; accepted 16 November 2002. 相似文献
28.
Summary Among alkaloids the pyrrolizidine alkaloids (PAs) play a unique role in the interactions between plants and adapted insects. InSenecio spp. (Asteraceae) PAs are synthesized in the roots as alkaloidN-oxides which are specifically translocated into shootsvia the phloem-path and channeled to the preferred sites of storage (e.g. inflorescences) where they are stored in the cell vacuoles. In differentSenecio spp. senecionineN-oxide is produced as the common product of biosynthesis, which subsequentlyvia a number of simple but specific reactions is transformed into typical speciesspecific PA-patterns. Insects from diverse taxa sequester PAs for their own defense. Lepidopterans (e.g. arctiids such asTyria jacobaeae andCreatonotos transiens) may hydrolyze plant acquired ester-PAs and convert the resulting necine base into insect-specific PAs by esterification with an acid of their own metabolism. Adapted arctiids and the grasshopperZonocerus take up PAs in the state of the tertiary amine.N-Oxides are reduced in the guts prior to uptake. In the bodies the tertiary PAs are rapidlyN-oxidized by a specific mixed-function oxigenase and are maintained in theN-oxide state. The importance of the reversible interconversion of the nontoxicN-oxide (pro-toxine) into the toxic tertiary alkaloid is discussed as the specific feature of PAs in plant-insect interactions. 相似文献
29.
Summary 7-spot ladybirds secrete alkaloid (coccinelline)-rich fluid (reflex blood) from leg joints as a defence mechanism against predators. A technique is described that enables the collection and accurate quantification of reflex blood produced, and the amount of coccinelline therein. Coccinelline was found distributed throughout the body, although concentrated in the reflex blood. Reflex blood was collected from a large set of beetles at several time points. Significant variation was found among beetles in the amount of reflex blood produced (for males and for females corrected for body weight) and the coccinelline concentration of the reflex blood. The results are discussed in relation to automimicry and the maintenance of variation through energy trade-offs. The relationships between tendency to aggregate, ability to reflex bleed and the possession of aposematic coloration are also considered. 相似文献
30.
Summary American Acraeinae butterflies often ingest large amounts of dehydropyrrolizidine alkaloids (PAs) from their Asteraceae hostplants in both larval and adult stages, but do not normally store these compounds for defence, instead biosynthesizing large amounts of the cyanogenic glucoside linamarin in all stages. This defence syndrome (rejection of plant toxins andde novo synthesis of protective chemicals) is considered to be the most evolved among aposematic (unpalatable mimicry-model) butterflies, as are the Acraeinae and Heliconiini which also synthesize cyanogens. Storage or minimal processing of larval hostplant-derived defensive chemicals is widespread and characterizes the most primitive model groups; an intermediate series (Danainae/Ithomiinae) also obtains the principal defensive chemicals (PAs) from plants, but mostly in the adult stage. These syndromes are discussed and contrasted with the pattern seen in Chrysomelidae beetles, wherede novo synthesis is widespread and considered primitive.Originally presented at the 9th Meeting on Micromolecular Evolution, Systematics and Ecology (Ribeirão Preto, SP, April 1987); see also Brownet al. (1990) 相似文献