Population-associated heterogeneity of the digestive Cys protease complement in Colorado potato beetle, Leptinotarsa decemlineata.

Herbivorous insects use complex protease complements to process plant proteins, useful to adjust their digestive functions to the plant diet and to elude the antidigestive effects of dietary protease inhibitors. We here assessed whether basic profiles and diet-related adjustments of the midgut protease complement may vary among populations of the insect herbivore Colorado potato beetle (Leptinotarsa decemlineata). Two laboratory colonies of this insect were used as models, derived from insect samples collected in potato fields ∼1200km distant from each other in North America.

Functional proteomics-aided selection of protease inhibitors for herbivore insect control.

Studies have reported the potential of protease inhibitors to engineer insect resistance in transgenic plants but the general usefulness of this approach in crop protection still remains to be established. Insects have evolved strategies to cope with dietary protease inhibitors, such as the use of proteases recalcitrant to inhibition, that often make the selection of effective inhibitors very challenging. Here, we used a functional proteomics approach for the 'capture' of Cys protease targets in crude protein extracts as a tool to identify promising cystatins for plant improvement.

Single substitutions to closely related amino acids contribute to the functional diversification of an insect-inducible, positively selected plant cystatin.

A causal link has been reported between positively selected amino acids in plant cystatins and the inhibitory range of these proteins against insect digestive cysteine (Cys) proteases. Here we assessed the impact of single substitutions to closely related amino acids on the contribution of positive selection to cystatin diversification. Cystatin sequence alignments, while confirming hypervariability, indicated a preference for related amino acids at positively selected sites.

Positive selection of digestive Cys proteases in herbivorous Coleoptera.

Positive selection is thought to contribute to the functional diversification of insect-inducible protease inhibitors in plants in response to selective pressures exerted by the digestive proteases of their herbivorous enemies. Here we assessed whether a reciprocal evolutionary process takes place on the insect side, and whether ingestion of a positively selected plant inhibitor may translate into a measurable rebalancing of midgut proteases in vivo. Midgut Cys proteases of herbivorous Coleoptera, including the major pest Colorado potato beetle (Leptinotarsa decemlineata), were first compared using a codon-based evolutionary model to look for the occurrence of hypervariable, positively selected amino acid sites among the tested sequences.

Survival to parasitoids in an insect hosting defensive symbionts: a multivariate approach to polymorphic traits affecting host use by its natural enemy.

Insect parasitoids and their insect hosts represent a wide range of parasitic trophic relations that can be used to understand the evolution of biotic diversity on earth. Testing theories of coevolution between hosts and parasites is based on factors directly involved in host susceptibility and parasitoid virulence. We used controlled encounters with potential hosts of the Aphidius ervi wasp to elucidate behavioral and other phenotypic traits of host Acyrthosiphon pisum that most contribute to success or failure of parasitism.

Wounding, insect chewing and phloem sap feeding differentially alter the leaf proteome of potato, Solanum tuberosum L.

Background: Various factors shape the response of plants to herbivorous insects, including wounding patterns, specific chemical effectors and feeding habits of the attacking herbivore. Here we performed a comparative proteomic analysis of the plant's response to wounding and herbivory, using as a model potato plants (Solanum tuberosum L.) subjected to mechanical wounding, defoliation by the Colorado potato beetle Leptinotarsa decemlineata Say, or phloem sap feeding by the potato aphid Macrosiphum euphorbiae Thomas.

Early presence of an enolase in the oviposition injecta of the aphid parasitoid Aphidius ervi analyzed with chitosan beads as artificial hosts.

Maternal factors of female wasps that are injected into hosts with their eggs at oviposition play a major role in strategies used by insect parasitoids to overcome host immunity, and to regulate host physiology during early stages of parasitism. Here, we attempted to precisely determine and compare the protein patterns injected by the endoparasitoid Aphidius ervi into two different host systems. Chitosan beads of aphid size designed as artificial and physiologically inert hosts were used as oviposition medium, to be compared with the natural aphid host as young nymphs of Macrosiphum euphorbiae.

Diversity of molecular transformations involved in the formation of spider silks.

Spiders that spin orb webs secrete seven types of silk. Although the spinning process of the dragline thread is beginning to be understood, the molecular events that occur in spiders' opisthosomal glands, which produce the other fibers, are unknown due to a lack of data regarding their initial and final structures. Taking advantage of the efficiency of Raman spectromicroscopy in investigating micrometer-sized biological samples, we have determined the secondary structure of proteins in the complete set of glands of the orb-weaving spider Nephila clavipes.

Selected beetle assemblages captured in pitfall traps baited with deer dung or meat in balsam fir and sugar maple forests of central Quebec.

Vertebrate dung and carrion are rich and strongly attractive resources for numerous beetles that are often closely linked to them. The presence and abundance of beetles exploiting such resources are influenced by various ecological factors including climate and forest cover vegetation. We studied selected assemblages of coprophilous and necrophagous beetles in Quebec along a 115-km north-south transect in three balsam fir (Abies balsamea (L.

Recombinant protease inhibitors for herbivore pest control: a multitrophic perspective.

Protease inhibitors are a promising complement to Bt toxins for the development of insect-resistant transgenic crops, but their limited specificity against proteolytic enzymes and the ubiquity of protease-dependent processes in living organisms raise questions about their eventual non-target effects in agroecosystems. After a brief overview of the main factors driving the impacts of insect-resistant transgenic crops on non-target organisms, the possible effects of protease inhibitors are discussed from a multitrophic perspective, taking into account not only the target herbivore proteases but also the proteases of other organisms found along the trophic chain, including the plant itself. Major progress has been achieved in recent years towards the design of highly potent broad-spectrum inhibitors and the field deployment of protease inhibitor-expressing transgenic plants resistant to major herbivore pests.

Impact of environmental stress on aphid clonal resistance to parasitoids: Role of Hamiltonella defensa bacterial symbiosis in association with a new facultative symbiont of the pea aphid.

Resistance to endoparasitoids in aphids involves complex interactions between insect and microbial players. It is now generally accepted that the facultative bacterial symbiont Hamiltonella defensa of the pea aphid Acyrthosiphon pisum is implicated in its resistance to the parasitoid Aphidius ervi. It has also been shown that heat negatively affects pea aphid resistance, suggesting the thermosensitivity of its defensive symbiosis.

Tranosema rostrale ichnovirus repeat element genes display distinct transcriptional patterns in caterpillar and wasp hosts.

The endoparasitic wasp Tranosema rostrale transmits an ichnovirus to its lepidopteran host, Choristoneura fumiferana, during parasitization. As shown for other ichnoviruses, the segmented dsDNA genome of the T. rostrale ichnovirus (TrIV) features several multi-gene families, including the repeat element (rep) family, whose products display no known similarity to non-ichnovirus proteins, except for a homologue encoded by the genome of the Helicoverpa armigera granulovirus; their functions remain unknown.

A proteomic analysis of the aphid Macrosiphum euphorbiae under heat and radiation stress.

Temperature and solar radiation can be important sources of abiotic stress for small herbivorous insects living in close association with plants. We examined the effects of daily fluctuations of heat and UV radiation on the proteome and performance of winged and wingless morphs of the aphid Macrosiphum euphorbiae. A daily regime of 4h of heat stress at 35 degrees C had more negative effects on the aphid's fitness than a similar period of UV-B stress (11.

Conformational and orientational transformation of silk proteins in the major ampullate gland of Nephila clavipes spiders.

The orientational and conformational transformation of the native liquid silk into a solid fiber in the major ampullate gland of the spider Nephila clavipes has been studied by Raman spectromicroscopy. The spectra show that the conformation of silk proteins in the glandular sac contains several secondary structure elements, which is consistent with intrinsically unfolded proteins. A few alpha-helices are also present and involve some alanine residues located in the polyalanine segments of the spidroin sequence.

Proteomes of the aphid Macrosiphum euphorbiae in its resistance and susceptibility responses to differently compatible parasitoids.

Host insects are either susceptible or resistant to parasitoids, where resistant hosts express immunity factors and compatible parasitoids express virulence factors that may reveal the manipulation of susceptible hosts. Using proteomics we compared responses of the same host, the aphid Macrosiphum euphorbiae, challenged by a well-adapted parasitoid Aphidius nigripes or by a less adapted relative, Aphidius ervi. The host was found to be equally acceptable to both parasitoids, but while A.

Tailoring the specificity of a plant cystatin toward herbivorous insect digestive cysteine proteases by single mutations at positively selected amino acid sites.

Plant cystatins, similar to other defense proteins, include hypervariable, positively selected amino acid sites presumably impacting their biological activity. Using 29 single mutants of the eighth domain of tomato (Solanum lycopersicum) multicystatin, SlCYS8, we assessed here the potential of site-directed mutagenesis at positively selected amino acid sites to generate cystatin variants with improved inhibitory potency and specificity toward herbivorous insect digestive cysteine (Cys) proteases. Compared to SlCYS8, several mutants (22 out of 29) exhibited either improved or lowered potency against different model Cys proteases, strongly suggesting the potential of positively selected amino acids as target sites to modulate the inhibitory specificity of the cystatin toward Cys proteases of agronomic significance.

Proteomic profiling of a parasitic wasp exposed to constant and fluctuating cold exposure.

When insects are exposed to fluctuating thermal regimes (FTRs) (i.e., cold exposure alternating with periodic short pulses to high temperature), in contrast to constant low temperature (CLT), mortality due to accumulation of chill injuries is markedly reduced.

In situ conformation of spider silk proteins in the intact major ampullate gland and in solution.

To understand the spinning process of dragline silk by spiders, the protein conformation before spinning has to be determined. Raman confocal spectromicroscopy has been used to study the conformation of the proteins in situ in the intact abdominal major ampullate gland of Nephila clavipes and Araneus diadematus spiders. The spectra obtained are typical of natively unfolded proteins and are very similar to that of a mixture of recombinant silk proteins.

Proteomic profiling of aphid Macrosiphum euphorbiae responses to host-plant-mediated stress induced by defoliation and water deficit.

Abiotic and biotic host-plant stress, such as desiccation and herbivory, may strongly affect sap-sucking insects such as aphids via changes in plant chemicals of insect nutritional or plant defensive value. Here, we examined (i) water deprivation and (ii) defoliation by the beetle Leptinotarsa decemlineata as stresses indirectly affecting the aphid Macrosiphum euphorbiae via its host plant Solanum tuberosum. For plant-induced stress, aphids were reared on healthy vs.

Temperature-mediated relationship between western flower thrips (Thysanoptera: Thripidae) and chrysanthemum.

Modeling the effect of temperature on the sustainability of insect-plant interactions requires assessment of both insect and plant performance. We examined the effect of temperature on western flower thrips, Frankliniella occidentalis (Pergande), a generalist herbivore with a high reproductive rate, and chrysanthemum inflorescences, a high quality but relatively fixed, ephemeral resource for thrips population growth. We hypothesized that different thrips versus plant responses to temperature result in significant statistical interaction of temperature with thrips abundance and flower damage attributes over time.

Comparative use of Mindarus abietinus (Homoptera: Aphididae) by two coccinellids (Coleoptera: Coccinellidae), the native Anatis mali and the exotic Harmonia axyridis, in a Christmas tree plantation.

The exotic coccinellid Harmonia axyridis (Pallas) recently expanded its range into eastern Canada and elsewhere in North America. We hypothesized that this coccinellid should be less well adapted to the prey Mindarus abietinus Koch. on balsam fir trees than the native coccinellid Anatis mali (Say), which evolved in close association with aphids on conifers in North America.

A multicomponent, elicitor-inducible cystatin complex in tomato, Solanum lycopersicum.

We assessed the ability of the fungal elicitor arachidonic acid to induce cystatin genes in tomato (Solanum lycopersicum), using a cDNA expression library from arachidonate-treated leaves. The cDNAs of two novel cystatins were isolated, coding for an approx. 11-kDa protein, SlCYS10; and for a 23.

Aphid clonal resistance to a parasitoid fails under heat stress.

Parasitoid virulence and host resistance are complex interactions depending on metabolic rate and cellular activity, which in aphids additionally implicate heritable secondary symbionts among the Enterobacteriaceae. As performance of the parasitoid, the aphid host and its symbionts may differentially respond to temperature, the success or failure of aphid parasitism is difficult to predict when temperature varies. We tested the hypothesis that resistance of the pea aphid Acyrthosiphon pisum to the parasitoid Aphidius ervi, which is linked to aphid secondary symbionts, may depend on temperature in several resistant and non-resistant aphid clonal lineages of different geographic origin and of known bacterial symbiosis, using experiments in controlled environments.

A hybrid, broad-spectrum inhibitor of Colorado potato beetle aspartate and cysteine digestive proteinases.

Protein engineering approaches are currently being devised to improve the inhibitory properties of plant proteinase inhibitors against digestive proteinases of herbivorous insects. Here we engineered a potent hybrid inhibitor of aspartate and cysteine digestive proteinases found in the Colorado potato beetle, Leptinotarsa decemlineata Say. Three cathepsin D inhibitors (CDIs) from stressed potato and tomato were first compared in their potency to inhibit digestive cathepsin D-like activity of the insect.

Colorado potato beetles show differential digestive compensatory responses to host plants expressing distinct sets of defense proteins.

Herbivorous insects fed plants expressing proteinase inhibitors (PIs) compensate for the loss of digestive proteolytic functions by producing novel proteinases. We assessed here whether such compensatory responses represent a general, non-specific adaptation to defense-related proteins in host plant tissues, or if distinct responses occur depending on the stress exerted on the plant. As a model, growth, development, and digestive proteases of the Colorado potato beetle (Leptinotarsa decemlineata Say) were monitored after feeding larvae with plants pre-treated with either methyl jasmonate or arachidonic acid, two compounds inducing different sets of defense genes in potato.