The genome sequence of the grape phylloxera provides insights into the evolution, adaptation, and invasion routes of an iconic pest.

Background: Although native to North America, the invasion of the aphid-like grape phylloxera Daktulosphaira vitifoliae across the globe altered the course of grape cultivation. For the past 150 years, viticulture relied on grafting-resistant North American Vitis species as rootstocks, thereby limiting genetic stocks tolerant to other stressors such as pathogens and climate change. Limited understanding of the insect genetics resulted in successive outbreaks across the globe when rootstocks failed.

Insect Mouthpart Transcriptome Unveils Extension of Cuticular Protein Repertoire and Complex Organization.

Insects have developed intriguing cuticles with very specific structures and functions, including microstructures governing their interactions with transmitted microbes, such as in aphid mouthparts harboring virus receptors within such microstructures. Here, we provide the first transcriptome analysis of an insect mouthpart cuticle ("retort organs" [ROs], the stylets' precursors). This analysis defined stylets as a complex composite material.

Bacteriocyte Reprogramming to Cope With Nutritional Stress in a Phloem Sap Feeding Hemipteran, the Pea Aphid .

Nutritional symbioses play a central role in the ability of insects to thrive on unbalanced diets and in ensuring their evolutionary success. A genomic model for nutritional symbiosis comprises the hemipteran , and the gamma-3-proteobacterium, , with genomes encoding highly integrated metabolic pathways. feeds exclusively on plant phloem sap, a nutritionally unbalanced diet highly variable in composition, thus raising the question of how this symbiotic system responds to nutritional stress.

The interaction of the bioinsecticide PA1b (Pea Albumin 1 subunit b) with the insect V-ATPase triggers apoptosis.

PA1b (Pea Albumin 1, subunit b) peptide is an entomotoxin, extracted from Legume seeds, with a lethal activity towards several insect pests, such as mosquitoes, some aphids and cereal weevils. This toxin acts by binding to the subunits c and e of the plasma membrane H-ATPase (V-ATPase) in the insect midgut. In this study, two cereal weevils, the sensitive Sitophilus oryzae strain WAA42, the resistance Sitophilus oryzae strain ISOR3 and the insensitive red flour beetle Tribolium castaneum, were used in biochemical and histological experiments to demonstrate that a PA1b/V-ATPase interaction triggers the apoptosis mechanism, resulting in insect death.

Synthesis of new dicinnamoyl 4-deoxy quinic acid and methyl ester derivatives and evaluation of the toxicity against the pea aphid Acyrthosiphon pisum.

New dicinnamoyl (caffeoyl, feruloyl, ortho and para-coumaroyl) 4-deoxyquinic acid and esters were synthesized by using a new 4-deoxy quinic acid triol intermediate. The optimisation of both coupling and deprotection steps allowed the preparation in good yields of the target products either as the carboxylic acid or the methyl ester form. Eight new compounds were evaluated for their ability to influence the feeding behaviour of the pea aphid Acyrthosiphon pisum.

New Cyt-like δ-endotoxins from Dickeya dadantii: structure and aphicidal activity.

In the track of new biopesticides, four genes namely cytA, cytB, cytC and cytD encoding proteins homologous to Bacillus thuringiensis (Bt) Cyt toxins have been identified in the plant pathogenic bacteria Dickeya dadantii genome. Here we show that three Cyt-like δ-endotoxins from D. dadantii (CytA, CytB and CytC) are toxic to the pathogen of the pea aphid Acyrthosiphon pisum in terms of both mortality and growth rate.

New insight into the RNA interference response against cathepsin-L gene in the pea aphid, Acyrthosiphon pisum: molting or gut phenotypes specifically induced by injection or feeding treatments.

RNA interference (RNAi) has been widely and successfully used for gene inactivation in insects, including aphids, where dsRNA administration can be performed either by feeding or microinjection. However, several aspects related to the aphid response to RNAi, as well as the influence of the administration method on tissue response, or the mixed success to observe phenotypes specific to the gene targeted, are still unclear in this insect group. In the present study, we made the first direct comparison of two administration methods (injection or feeding) for delivery of dsRNA targeting the cathepsin-L gene in the pea aphid, Acyrthosiphon pisum.

Expression and biological activity of the cystine knot bioinsecticide PA1b (Pea Albumin 1 Subunit b).

The PA1b (Pea Albumin 1, subunit b) peptide is an entomotoxin extract from Legume seeds with lethal activity on several insect pests, such as mosquitoes, some aphids and cereal weevils. This 37 amino-acid cysteine-rich peptide has been, until now, obtained by biochemical purification or chemical synthesis. In this paper, we present our results for the transient production of the peptide in Nicotiana benthamiana by agro-infiltration, with a yield of about 35 µg/g of fresh leaves and maximum production 8 days after infiltration.

Tyrosine pathway regulation is host-mediated in the pea aphid symbiosis during late embryonic and early larval development.

Background: Nutritional symbioses play a central role in insects' adaptation to specialized diets and in their evolutionary success. The obligatory symbiosis between the pea aphid, Acyrthosiphon pisum, and the bacterium, Buchnera aphidicola, is no exception as it enables this important agricultural pest insect to develop on a diet exclusively based on plant phloem sap. The symbiotic bacteria provide the host with essential amino acids lacking in its diet but necessary for the rapid embryonic growth seen in the parthenogenetic viviparous reproduction of aphids.

Transcriptome of Dickeya dadantii infecting Acyrthosiphon pisum reveals a strong defense against antimicrobial peptides.

The plant pathogenic bacterium Dickeya dadantii has recently been shown to be able to kill the aphid Acyrthosiphon pisum. While the factors required to cause plant disease are now well characterized, those required for insect pathogeny remain mostly unknown. To identify these factors, we analyzed the transcriptome of the bacteria isolated from infected aphids.

Exceptional plant penetration and feeding upon cortical parenchyma cells by the woolly poplar aphid.

Forty percent of aphids live wholly or partly on trees, most species being associated with leaves or petioles. Species able to exploit woody parts have either specific adaptations, such as extra long stylets that allow them to reach the phloem, or the ability to induce galls. The woolly poplar aphid, Phloeomyzus passerinii (Signoret) (Hemiptera: Aphididae), colonizes the trunks and base of the lower branches of mature poplars and causes cortical necrosis leading to the death of trees where infestation is heavy.

Dickeya dadantii, a plant pathogenic bacterium producing Cyt-like entomotoxins, causes septicemia in the pea aphid Acyrthosiphon pisum.

Dickeya dadantii (syn. Erwinia chrysanthemi) is a plant pathogenic bacteria that harbours a cluster of four horizontally-transferred, insect-specific toxin genes. It was recently shown to be capable of causing an acute infection in the pea aphid Acyrthosiphon pisum (Insecta: Hemiptera).

A genomic reappraisal of symbiotic function in the aphid/Buchnera symbiosis: reduced transporter sets and variable membrane organisations.

Buchnera aphidicola is an obligate symbiotic bacterium that sustains the physiology of aphids by complementing their exclusive phloem sap diet. In this study, we reappraised the transport function of different Buchnera strains, from the aphids Acyrthosiphon pisum, Schizaphis graminum, Baizongia pistaciae and Cinara cedri, using the re-annotation of their transmembrane proteins coupled with an exploration of their metabolic networks. Although metabolic analyses revealed high interdependencies between the host and the bacteria, we demonstrate here that transport in Buchnera is assured by low transporter diversity, when compared to free-living bacteria, being mostly based on a few general transporters, some of which probably have lost their substrate specificity.

Multimodal dynamic response of the Buchnera aphidicola pLeu plasmid to variations in leucine demand of its host, the pea aphid Acyrthosiphon pisum.

Aphids, important agricultural pests, can grow and reproduce thanks to their intimate symbiosis with the γ-proteobacterium Buchnera aphidicola that furnishes them with essential amino acids lacking in their phloem sap diet. To study how B. aphidicola, with its reduced genome containing very few transcriptional regulators, responds to variations in the metabolic requirements of its host, we concentrated on the leucine metabolic pathway.

Triterpene saponins of Quillaja saponaria show strong aphicidal and deterrent activity against the pea aphid Acyrthosiphon pisum.

Background: Saponins are a class of secondary plant metabolites consisting of a sugar moiety glycosidically linked to a hydrophobic aglycone (sapogenin) that often possess insecticidal activities. Four saponins were selected: two triterpene saponins, Q. saponaria saponins and aescin, and two steroidal saponins, digitonin and diosgenin.

CycADS: an annotation database system to ease the development and update of BioCyc databases.

In recent years, genomes from an increasing number of organisms have been sequenced, but their annotation remains a time-consuming process. The BioCyc databases offer a framework for the integrated analysis of metabolic networks. The Pathway tool software suite allows the automated construction of a database starting from an annotated genome, but it requires prior integration of all annotations into a specific summary file or into a GenBank file.

Cyt toxin expression reveals an inverse regulation of insect and plant virulence factors of Dickeya dadantii.

The plant pathogenic bacteria Dickeya dadantii is also a pathogen of the pea aphid Acyrthosiphon pisum. The genome of the bacteria contains four cyt genes, encoding homologues of Bacillus thuringiensis Cyt toxins, which are involved in its pathogenicity to insects. We show here that these genes are transcribed as an operon, and we determined the conditions necessary for their expression.

Binding properties of the N-acetylglucosamine and high-mannose N-glycan PP2-A1 phloem lectin in Arabidopsis.

Phloem Protein2 (PP2) is a component of the phloem protein bodies found in sieve elements. We describe here the lectin properties of the Arabidopsis (Arabidopsis thaliana) PP2-A1. Using a recombinant protein produced in Escherichia coli, we demonstrated binding to N-acetylglucosamine oligomers.

Immunity and other defenses in pea aphids, Acyrthosiphon pisum.

Background: Recent genomic analyses of arthropod defense mechanisms suggest conservation of key elements underlying responses to pathogens, parasites and stresses. At the center of pathogen-induced immune responses are signaling pathways triggered by the recognition of fungal, bacterial and viral signatures. These pathways result in the production of response molecules, such as antimicrobial peptides and lysozymes, which degrade or destroy invaders.

Systemic analysis of the symbiotic function of Buchnera aphidicola, the primary endosymbiont of the pea aphid Acyrthosiphon pisum.

Buchnera aphidicola is the primary obligate intracellular symbiont of most aphid species. B. aphidicola and aphids have been evolving in parallel since their association started, about 150 Myr ago.

Effects of Bacillus thuringiensis delta-endotoxins on the pea aphid (Acyrthosiphon pisum).

Four Bacillus thuringiensis delta-endotoxins, Cry3A, Cry4Aa, Cry11Aa, and Cyt1Aa, were found to exhibit low to moderate toxicity on the pea aphid, Acyrthosiphon pisum, in terms both of mortality and growth rate. Cry1Ab was essentially nontoxic except at high rates. To demonstrate these effects, we had to use exhaustive buffer-based controls.

Toxicity, binding and internalization of the pea-A1b entomotoxin in Sf9 cells.

PA1b (Pea Albumin 1b) is a peptide toxin lethal for certain insects. This paper shows that the cultured insect cells Sf9 are sensitive to the toxin and display a high-affinity binding site for PA1b. Mammalian cells are not sensitive and no binding activity was detected.

Conservation of the links between gene transcription and chromosomal organization in the highly reduced genome of Buchnera aphidicola.

Background: Genomic studies on bacteria have clearly shown the existence of chromosomal organization as regards, for example, to gene localization, order and orientation. Moreover, transcriptomic analyses have demonstrated that, in free-living bacteria, gene transcription levels and chromosomal organization are mutually influenced. We have explored the possible conservation of relationships between mRNA abundances and chromosomal organization in the highly reduced genome of Buchnera aphidicola, the primary endosymbiont of the aphids, and a close relative to Escherichia coli.