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Chemical Defenses (chemical + defense)
Selected AbstractsHow to Produce a Chemical Defense: Structural Elucidation and Anatomical Distribution of Aplysioviolin and Phycoerythrobilin in the Sea Hare Aplysia californicaCHEMISTRY & BIODIVERSITY, Issue 5 2010Michiya Kamio Abstract We previously used bioassay-guided fractionation to identify phycoerythrobilin (1) and its monomethyl ester, aplysioviolin (2), as components in the ink secretion of a marine gastropod, the sea hare Aplysia californica, that act as chemical deterrents against predatory blue crabs. This was the first report of 1 as a natural product. Compound 2 was previously reported as a natural product from three species of Aplysia (A. fasciata, A. dactylomela, and A. parvula), but the reported structure and composition of stereoisomers of 2 are different among these species. Sea hares are thought to produce 2 from phycoerythrin, a photosynthetic pigment in their red-algal diet composed of a phycobiliprotein covalently linked to the chromophore 1, by cleavage of the covalent bond and methylation of 1, but neither the sequence nor the anatomical location of the cleavage and methylation is known. In this study, we clarify the structure of 1 and 2 in ink secretion of A. californica, and describe the distribution of 1 and 2 in the tissues of sea hares. We conclude that cleavage of the covalent bond in phycoerythrin occurs first, forming 1 in the digestive gland, followed by methylation of 1 to yield 2 in the ink gland. [source] Global Change Effects on Plant Chemical Defenses against Insect HerbivoresJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 11 2008M. Gabriela Bidart-Bouzat Abstract This review focuses on individual effects of major global change factors, such as elevated CO2, O3, UV light and temperature, on plant secondary chemistry. These secondary metabolites are well-known for their role in plant defense against insect herbivory. Global change effects on secondary chemicals appear to be plant species-specific and dependent on the chemical type. Even though plant chemical responses induced by these factors are highly variable, there seems to be some specificity in the response to different environmental stressors. For example, even though the production of phenolic compounds is enhanced by both elevated CO2 and UV light levels, the latter appears to primarily increase the concentrations of flavonoids. Likewise, specific phenolic metabolites seem to be induced by O3 but not by other factors, and an increase in volatile organic compounds has been particularly detected under elevated temperature. More information is needed regarding how global change factors influence inducibility of plant chemical defenses as well as how their indirect and direct effects impact insect performance and behavior, herbivory rates and pathogen attack. This knowledge is crucial to better understand how plants and their associated natural enemies will be affected in future changing environments. [source] How to Spoil the Taste of Insect Prey?CHEMBIOCHEM, Issue 12 2010A Novel Feeding Deterrent against Ants Released by Larvae of the Alder Leaf Beetle, Agelastica alni Abstract Chemical defense of leaf beetle larvae (Chrysomelidae) against enemies is provided by secretions containing a wide range of deterrent compounds or by unpalatable hemolymph constituents. Here we report a new, very strong feeding deterrent against ants released by larvae of the alder leaf beetle Agelastica alni when attacked. The larvae release a defensive fluid from openings of pairwise, dorsolaterally located tubercles on the first to the eighth abdominal segments. The fluid, consisting of hemolymph and probably a glandular cell secretion, has previously been shown to contain a very stable, non-volatile feeding deterrent. The major deterrent component was isolated by repeated HPLC separation and analyzed by NMR and MS. The compound proved to be ,- L -glutamyl- L -2-furylalanine (1), a novel dipeptide containing the unusual amino acid L -2-furylalanine. This amino acid, although synthetically well known, has not previously been reported from natural sources. The absolute configuration of the natural compound was elucidated by enantioselective gas chromatography after derivatization. The structure of the dipeptide was verified by the synthesis of several isomeric dipeptides. In bioassays a concentration of 1 ,g,,L,1 was sufficient to deter polyphagous Myrmica rubra ants from feeding. [source] WARNING DISPLAYS IN SPINY ANIMALS: ONE (MORE) EVOLUTIONARY ROUTE TO APOSEMATISMEVOLUTION, Issue 12 2005Michael P. Speed Abstract To date, theoretical or laboratory simulations of aposematic evolution in prey animals have focused narrowly on internally stored chemical defense as the source of unprofitability and ignore aposematic advertisement of physical defenses such as spines (and defensive hairs, claws, etc.). This has occurred even though aposematism in spiny animals has been recognized since the 19th century. In this paper we present the first detailed theoretical consideration of aposematism in spiny animals, focusing on questions of initial evolution, costs of display, and coevolution of displays with defenses. Using an individual-based evolutionary model, we found that spines (or similar physical defenses) can easily evolve without aposematism, but when spines do evolve, aposematic displays can also easily evolve if they help to make the prey animal distinctive and if they draw attention to the physical threat. When aposematic displays evolve, they cause reduced investment in costly spines, so that, in addition to signaling unprofitability, aposematic display may enhance the cost-effectiveness of antipredator defenses (one exception to this conclusion is if the display is itself as costly as the defense). For animals with stinging spines, combining physical and chemical defense, the evolution of aposematic display may lead to reduced investment in the toxin compared to the spine. This occurs because spines act as both secondary (repellent) defenses and as primary defenses (their own visible, honest advertisement), whereas internally stored toxins only (generally) act as repellent secondary defenses. We argue that conspicuous aposematism in spines functions as an attention-getting mechanism, whereas conspicuous aposematic display in purely toxic animals may be explained by signal reliability arguments. Finally, one (more) route by which aposematism may initially evolve is by spiny rather than purely chemically defended species, spreading to species with other forms of secondary defense as the signal becomes common. [source] Spatial association of photosynthesis and chemical defense in Arabidopsis thaliana following herbivory by Trichoplusia niPHYSIOLOGIA PLANTARUM, Issue 2 2009Jennie Tang Because they share common precursors and require significant amounts of energy, photosynthesis and defense against herbivores and pathogens may be inversely related. This relationship was examined in Arabidopsis thaliana exposed to herbivory by Trichoplusia ni neonates. The spatial pattern of photosynthesis was compared statistically with that of induction of the defense-related cinnamate-4-hydroxylase (C4H) gene across individual leaves exposed to herbivory in transgenic plants harboring a C4H:GUS gene fusion. In portions of the leaf where C4H:GUS expression was upregulated, photosynthesis was depressed, while non-photochemical quenching was increased, suggesting a trade-off between these two processes. However, photosynthetic damage spread further into surrounding areas than the induction of C4H:GUS expression. Photosynthetic depression was observed up to 1 mm from the edges of holes, whereas C4H:GUS induction typically was limited to about 0.5 mm or less from edges. Other mechanisms may be responsible for the spread of photosynthetic damage beyond where C4H-related defense was induced. Alternatively, C4H induction may reflect a subset of defensive responses more limited in their spatial distribution than the downregulation of photosynthesis. The suppression of photosynthesis in remaining leaf tissue represents a ,hidden cost' of herbivore damage. [source] Evolution of latex and its constituent defensive chemistry in milkweeds (Asclepias): a phylogenetic test of plant defense escalationENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 1 2008Anurag A. Agrawal Abstract A tremendous diversity of plants exude sticky and toxic latex upon tissue damage, and its production has been widely studied as a defensive adaptation against insect herbivores. Here, we address variation in latex production and its constituent chemical properties (cardenolides and cysteine proteases) in 53 milkweeds [Asclepias spp. (Apocynaceae)], employing a phylogenetic approach to test macroevolutionary hypotheses of defense evolution. Species were highly variable for all three traits, and they showed little evidence for strong phylogenetic conservatism. Latex production and the constituent chemical defenses are thus evolutionarily labile and may evolve rapidly. Nonetheless, in phylogenetically independent analyses, we show that the three traits show some correlations (and thus share a correlated evolutionary history), including a positive correlation between latex exudation and cysteine protease activity. Conversely, latex exudation and cysteine protease activity both showed a trade-off with cardenolide concentrations in latex. We also tested whether these traits have increased in their phenotypic values as the milkweeds diversified, as predicted by plant defense escalation theory. Alternative methods of testing this prediction gave conflicting results , there was an overall negative correlation between amount of evolutionary change and amount of latex exudation; however, ancestral state reconstructions indicated that most speciation events were associated with increases in latex. We conclude by (i) summarizing the evidence of milkweed latex itself as a multivariate defense including the amount exuded and toxin concentrations within, (ii) assessing the coordinated evolution of latex traits and how this fits with our previous notion of ,plant defense syndromes', and finally, (iii) proposing a novel hypothesis that includes an ,evolving community of herbivores' that may promote the escalation or decline of particular defensive strategies as plant lineages diversify. [source] Global Change Effects on Plant Chemical Defenses against Insect HerbivoresJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 11 2008M. Gabriela Bidart-Bouzat Abstract This review focuses on individual effects of major global change factors, such as elevated CO2, O3, UV light and temperature, on plant secondary chemistry. These secondary metabolites are well-known for their role in plant defense against insect herbivory. Global change effects on secondary chemicals appear to be plant species-specific and dependent on the chemical type. Even though plant chemical responses induced by these factors are highly variable, there seems to be some specificity in the response to different environmental stressors. For example, even though the production of phenolic compounds is enhanced by both elevated CO2 and UV light levels, the latter appears to primarily increase the concentrations of flavonoids. Likewise, specific phenolic metabolites seem to be induced by O3 but not by other factors, and an increase in volatile organic compounds has been particularly detected under elevated temperature. More information is needed regarding how global change factors influence inducibility of plant chemical defenses as well as how their indirect and direct effects impact insect performance and behavior, herbivory rates and pathogen attack. This knowledge is crucial to better understand how plants and their associated natural enemies will be affected in future changing environments. [source] Opisthonotal glands in the Camisiidae (Acari, Oribatida): evidence for a regressive evolutionary trendJOURNAL OF ZOOLOGICAL SYSTEMATICS AND EVOLUTIONARY RESEARCH, Issue 1 2009G. Raspotnig Abstract Paired, sac-like and typically large opisthonotal glands (syn. oil glands), mainly considered for chemical protection and communication, characterize the so-called ,glandulate Oribatida' which include the Parhyposomata, Mixonomata, Desmonomata and Brachypylina but also the Astigmata. Among these groups distinct evolutionary trends affect the morphology of glands and their secretion profiles, thereby rendering them highly informative characters with phylogenetic significance. One striking tendency, convergently occurring in a few glandulate groups, leads to the degeneration or even complete regression of opisthonotal glands. In this study, a first example of coherent evolutionary steps towards opisthonotal gland degeneration is described by using desmonomatan Camisiidae as a model: Opisthonotal glands in representatives of genus Platynothrus still show morphologically and chemically ancient conditions with fairly-well developed glandular reservoirs. Secretion patterns mainly consist of a characteristic set of terpenes and aromatics (,astigmatid compounds') as found in outgroups such as desmonomatan Trhypochthoniidae. Progressive states of regression of opisthonotal glands, along with a reduction of component-richness and amounts of secretions, occur in representatives of Heminothrus and, more conspicuously, in species of Camisia, most likely indicating a consistent evolutionary trend. This trend towards opisthonotal gland atrophy may be due to novel alternative and cheap strategies of passive defense in more-derivative camisiids , such as mechanical protection by encrustation of the cuticle , that possibly compensate for the lack of chemical defenses. Zusammenfassung Paarige, sackförmige und typischerweise große opisthosomatische Drüsen (syn. Öldrüsen), deren Sekrete hauptsächlich zum chemischen Schutz und zur Kommunikation dienen sollen, kennzeichnen die sogenannten glandulaten Hornmilben. Innerhalb dieser Hornmilbengruppe, die die Parhyposomata, Mixonomata, Desmonomata, Brachypylina, aber auch die astigmaten Milben umfasst, waren die Öldrüsen offensichtlich in morphologischer und chemischer Hinsicht deutlich unterschiedlichen evolutiven Trends unterworfen; damit sind Öldrüsen ein phylogenetisch außerordentlich wichtiger Merkmalskomplex in der Oribatiden-Systematik geworden. Eine auffällige Tendenz allerdings, die offensichtlich mehrmals konvergent auftritt, führt zur Rückbildung der Drüsen in bestimmten glandulaten Gruppen. In der vorliegenden Arbeit wird zum ersten Mal eine zusammenhängende Linie solcher Rückbildungsstadien am Beispiel der Camisiidae (Desmonomata) beschrieben: die weitgehend noch gut ausgebildeten Öldrüsen von Vertretern der Gattung Platynothrus zeigen morphologisch und chemisch ursprüngliche Merkmale. Sekretprofile bestehen hauptsächlich aus einem charakteristischen Set von Terpenen und Aromaten ("astigmatid compounds'), das auch in Außengruppen wie z.B. bei Trhypochthoniiden auftritt. Fortschreitende Stadien der Rückbildung von Öldrüsen, verbunden mit einer Verarmung der Sekretprofile und einer Verringerung an Sekretmengen, treten in Vertretern von Heminothrus und, noch auffälliger, bei verschiedenen Arten von Camisia auf: dieses Phänomen, übereinstimmend mit einem auf morphologischen Daten basierenden Systemvorschlag, wird als evolutiver Trend innerhalb der Camisiidae gedeutet. Dieser Trend zur Öldrüsenrückbildung ist möglicherweise mit einer alternativen Strategie passiver Verteidigung bei weiter abgeleiteten Camisiiden zu erklären, die Krustenbildungen aus Cerotegument und Bodenpartikeln auf der Körperöberfläche als mechanischen Schutz gegen Prädatoren nützen. Diese möglicherweise energetisch billige Variante könnte den Verlust chemischer Verteidigung über Öldrüsensekretion kompensieren. [source] Symbiont-mediated changes in Lolium arundinaceum inducible defenses: evidence from changes in gene expression and leaf compositionNEW PHYTOLOGIST, Issue 3 2007Terrence J. Sullivan Summary ,,Plants have multiple strategies to deal with herbivory, ranging from chemical or physical defenses to tolerating damage and allocating resources for regrowth. Grasses usually tolerate herbivory, but for some cool-season grasses, their strategy may depend upon their interactions with intracellular symbionts. Neotyphodium endophytes are common symbionts in pooid grasses, and, for some host species, they provide chemical defenses against both vertebrate and invertebrate herbivores. ,,Here, it was tested whether defenses provided by Neotyphodium coenophialum in Lolium arundinaceum (tall fescue) are inducible by both mechanical damage and herbivory from an invertebrate herbivore, Spodoptera frugiperda (fall armyworm), via a bioassay and by quantifying mRNA expression for lolC, a gene required for loline biosysnthesis. ,,Both mechanical and herbivore damage had a negative effect on the reproduction of a subsequent herbivore, Rhopalosiphum padi (bird cherry-oat aphid), and herbivore damage caused an up-regulation of lolC. Uninfected grass hosts also had significantly higher foliar N% and lower C : N ratio compared with infected hosts, suggesting greater allocation to growth rather than defense. ,,For L. arundinaceum, N. coenophialum appears to switch its host's defensive strategy from tolerance via compensation to resistance. [source] Stream mosses as chemically-defended refugia for freshwater macroinvertebratesOIKOS, Issue 2 2007John D. Parker Marine and terrestrial studies show that small, sedentary herbivores that utilize plants as both food and habitat can gain enemy-free space by living on hosts that are chemically defended from larger, generalist consumers. Although large herbivores are increasingly recognized as important consumers of macrophytes in freshwater communities, the potential indirect effects of herbivory on plant-associated macroinvertebrates have rarely been studied. Here, we show that the large, generalist consumers in a riverine system, Canada geese, Branta canadensis, and crayfish, Procambarus spiculifer, both selectively consumed riverweed, Podostemum ceratophyllum, over an aquatic moss, Fontinalis novae-angliae, even though moss comprised 89% of the total plant biomass on riverine rocky shoals. Moss supported twice as many plant-associated macroinvertebrates as riverweed, suggesting that it might provide a spatial refuge from consumption by these larger consumers. Bioassay-guided fractionation of moss extracts led to the isolation of a C18 acetylenic acid, octadeca-9,12-dien-6-ynoic acid, that deterred crayfish feeding. In contrast to results with Canada geese and crayfish, both the amphipod Crangonyx gracilis and the isopod Asellus aquaticus consumed significant amounts of moss but rejected riverweed in laboratory feeding assays. Moreover, neither amphipod nor isopod feeding was deterred by the crude organic extract of Fontinalis, suggesting that these mesograzers tolerate or circumvent the chemical defenses that deterred larger consumers. Thus, herbivory by large, generalist herbivores may drive freshwater plant community structure towards chemically defended plants and favor the ecological specialization of smaller, less mobile herbivores on unpalatable hosts that represent enemy-free space. [source] | |||||||||||||