55 research outputs found
Transgressive segregation of primary and secondary metabolites in F2 hybrids between Jacobaea aquatica and J. vulgaris
Hybridization between plant species can have a number of biological consequences; interspecific hybridization has been tied to speciation events, biological invasions, and diversification at the level of genes, metabolites, and phenotypes. This study aims to provide evidence of transgressive segregation in the expression of primary and secondary metabolites in hybrids between Jacobaeavulgaris and J. aquaticus using an NMR-based metabolomic profiling approach. A number of F2 hybrid genotypes exhibited metabolomic profiles that were outside the range encompassed by parental species. Expression of a number of primary and secondary metabolites, including jacaronone analogues, chlorogenic acid, sucrose, glucose, malic acid, and two amino acids was extreme in some F2 hybrid genotypes compared to parental genotypes, and citric acid was expressed in highest concentrations in J. vulgaris. Metabolomic profiling based on NMR is a useful tool for quantifying genetically controlled differences between major primary and secondary metabolites among plant genotypes. Interspecific plant hybrids in general, and specifically hybrids between J. vulgaris and J. aquatica, will be useful for disentangling the ecological role of suites of primary and secondary metabolites in plants, because interspecific hybridization generates extreme metabolomic diversity compared to that normally observed between parental genotypes
Leafminer attack accelerates the development of soil‐dwelling conspecific pupae via plant‐mediated changes in belowground volatiles
Herbivore population dynamics are strongly influenced by the interactions established through their shared host. Such plant-mediated interactions can occur between different herbivore species and different life developmental stages of the same herbivore. However, whether these interactions occur between leaf-feeding herbivores and their soil-dwelling pupae is unknown.
We studied whether tomato (Solanum lycopersicum) leaf herbivory by the American serpentine leafminer Liriomyza trifolii affects the performance of conspecific pupae exposed to the soil headspace of the plant. To gain mechanistic insights, we performed insect bioassays with the jasmonate-deficient tomato mutant def-1 and its wild-type, along with phytohormones, gene expression and root volatiles analyses.
Belowground volatiles accelerated leafminer metamorphosis when wild-type plants were attacked aboveground by conspecifics. The opposite pattern was observed for def-1 plants, in which aboveground herbivory slowed metamorphosis. Leafminer attack induced jasmonate and abscisic acid accumulation and modulated volatile production in tomato roots in a def-1-dependent manner.
Our results demonstrate that aboveground herbivory triggers changes in root defence signalling and expression, which can directly or indirectly via changes in soil or microbial volatiles, alter pupal development time. This finding expands the repertoire of plant–herbivore interactions to herbivory-induced modulation of metamorphosis, with potential consequences for plant and herbivore community dynamics
Spontaneous annihilation of high-density matter in the electroweak theory
In the presence of fermionic matter the topologically distinct vacua of the
standard model are metastable and can decay by tunneling through the sphaleron
barrier. This process annihilates one fermion per doublet due to the anomalous
non-conservation of baryon and lepton currents and is accompanied by a
production of gauge and Higgs bosons. We present a numerical method to obtain
local bounce solutions which minimize the Euclidean action in the space of all
configurations connecting two adjacent topological sectors. These solutions
determine the decay rate and the configuration of the fields after the
tunneling. We also follow the real time evolution of this configuration and
analyze the spectrum of the created bosons. If the matter density exceeds some
critical value, the exponentially suppressed tunneling triggers off an
avalanche producing an enormous amount of bosons.Comment: 38 pages, 6 Postscript figure
Fermion sea along the sphaleron barrier
In this revised version we have improved the treatment of the top and bottom
quark mass. This leads to slight changes of the numerical results, especially
of those presented in Fig.4. The discussion of the numerical procedure and
accuracy has been extended.Comment: 39 pages (LaTex) plus 5 figures (uuencoded postscript files);
RUB-TPII-62/93, to appear in Phys.Rev.
Sphaleron transitions in the Minimal Standard Model and the upper bound for the Higgs Mass
We calculate the dissipation of the baryon number after the electroweak phase
transition due to thermal fluctuations above the sphaleron barrier. We consider
not only the classical Boltzmann factor but also fermionic and bosonic one-loop
contributions. We find that both bosonic and especially fermionic fluctuations
can considerably suppress the transition rate. Assuming the Langer--Affleck
formalism for this rate, the condition that an initial baryon asymmetry must
not be washed out by sphaleron transitions leads, in the Minimal Standard Model
(), to an upper bound for the Higgs mass in the range 60 to 75
GeV.Comment: 49 pages, 5 figures (uuencoded PostScript); fixing of the
renormalization scale has been improved, numerics has been extende
Winding Transitions at Finite Energy and Temperature: An O(3) Model
Winding number transitions in the two dimensional softly broken O(3)
nonlinear sigma model are studied at finite energy and temperature. New
periodic instanton solutions which dominate the semiclassical transition
amplitudes are found analytically at low energies, and numerically for all
energies up to the sphaleron scale. The Euclidean period beta of these finite
energy instantons increases with energy, contrary to the behavior found in the
abelian Higgs model or simple one dimensional systems. This results in a sharp
crossover from instanton dominated tunneling to sphaleron dominated thermal
activation at a certain critical temperature. Since this behavior is traceable
to the soft breaking of conformal invariance by the mass term in the sigma
model, semiclassical winding number transition amplitudes in the electroweak
theory in 3+1 dimensions should exhibit a similar sharp crossover. We argue
that this is indeed the case in the standard model for M_H < 4 M_W.Comment: 21 pages (14 figures), RevTeX (plus macro), uses eps
Species by Environment Interactions Affect Pyrrolizidine Alkaloid Expression in Senecio jacobaea, Senecio aquaticus, and Their Hybrids
We examined the effects of water and nutrient availability on the expression of the defense pyrrolizidine alkaloids (PAs) in Senecio jacobaea and S. aquaticus. Senecio jacobaea, and S. aquaticus are adapted to different natural habitats, characterized by differing abiotic conditions and different selection pressures from natural enemies. We tested if PA concentration and diversity are plastic over a range of water and nutrient treatments, and also whether such plasticity is dependent on plant species. We also tested the hypothesis that hybridization may contribute to PA diversity within plants, by comparing PA expression in parental species to that in artificially generated F1 hybrids, and also in later generation natural hybrids between S. jacobaea and S. aquaticus. We showed that total PA concentration in roots and shoots is not dependent on species, but that species determines the pattern of PA diversification. Pyrrolizidine alkaloid diversity and concentration are both dependent on environmental factors. Hybrids produce a putatively novel PA, and this PA is conserved in natural hybrids, that are backcrossed to S. jacobaea. Natural hybrids that are backcrossed several times to S. jacobaea are with regard to PA diversity significantly different from S. jacobaea but not from S. aquaticus, while F1 hybrids are in all cases more similar to S. jacobaea. These results collectively suggest that PA diversity is under the influence of natural selection
Metabolomic Plasticity in GM and Non-GM Potato Leaves in Response to Aphid Herbivory and Virus Infection
An important aspect of ecological safety of genetically
modified
(GM) plants is the evaluation of unintended effects on plant–insect
interactions. These interactions are to a large extent influenced
by the chemical composition of plants. This study uses NMR-based metabolomics
to establish a baseline of chemical variation to which differences
between a GM potato line and its parent cultivar are compared. The
effects of leaf age, virus infection, and aphid herbivory on plant
metabolomes were studied. The metabolome of the GM line differed from
its parent only in young leaves of noninfected plants. This effect
was small when compared to the baseline. Consistently, aphid performance
on excised leaves was influenced by leaf age, while no difference
in performance was found between GM and non-GM plants. The metabolomic
baseline approach is concluded to be a useful tool in ecological safety
assessment
An overview of NMR-based metabolomics to identify secondary plant compounds involved in host plant resistance
Secondary metabolites provide a potential source for the generation of host plant resistance and development of biopesticides. This is especially important in view of the rapid and vast spread of agricultural and horticultural pests worldwide. Multiple pests control tactics in the framework of an integrated pest management (IPM) programme are necessary. One important strategy of IPM is the use of chemical host plant resistance. Up to now the study of chemical host plant resistance has, for technical reasons, been restricted to the identification of single compounds applying specific chemical analyses adapted to the compound in question. In biological processes however, usually more than one compound is involved. Metabolomics allows the simultaneous detection of a wide range of compounds, providing an immediate image of the metabolome of a plant. One of the most universally used metabolomic approaches comprises nuclear magnetic resonance spectroscopy (NMR). It has been NMR which has been applied as a proof of principle to show that metabolomics can constitute a major advancement in the study of host plant resistance. Here we give an overview on the application of NMR to identify candidate compounds for host plant resistance. We focus on host plant resistance to western flower thrips (Frankliniella occidentalis) which has been used as a model for different plant species
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