Saliva is a critical biochemical interface between aphids and their host plants; however, the biochemical nature and physiological functions of aphid saliva proteins are not fully elucidated. In this study we used a multidisciplinary proteomics approach combining liquid chromatography-electrospray ionization tandem mass spectrometry and two-dimensional differential in-gel electrophoresis/matrix-assisted laser desorption/ionization time-of-flight/mass spectrometry to compare the salivary proteins from three aphid species including Acyrthosiphon pisum, Megoura viciae and Myzus persicae. Comparative analyses revealed variability among aphid salivary proteomes. Among the proteins that varied, 22% were related to DNA-binding, 19% were related to GTP-binding, and 19% had oxidoreductase activity. In addition, we identified a peroxiredoxin enzyme and an ATP-binding protein that may be involved in the modulation of plant defences. Knowledge of salivary components and how they vary among aphid species may reveal how aphids target plant processes and how the aphid and host plant interact.

Les pucerons, insectes ravageurs majeurs des forets, des cultures cerealieres, legumieres, maraicheres, fruitieres et ornementales, sont combattus essentiellement avec des insecticides de synthese. En raison de l'effet nocif de ces derniers sur l'environnement et du developpement de populations de pucerons resistants, il est primordial d'adopter des alternatives de lutte. La salive des insectes joue un role crucial dans leur alimentation. Elle contient une grande variete de composes dont la specificite d'action permet de dissequer certains mecanismes physiologiques qui regissent les interactions entre l'insecte et son hote. Certains composes induisent les defenses de leur hote et sont consideres comme des outils prometteurs dans la lutte contre les insectes ravageurs. Une des strategies envisageables repose sur la recherche et la valorisation de substances presentes dans la salive des pucerons. Cette approche a surtout ete developpee chez les insectes hematophages. L'etat des connaissances sur la salive des pucerons est expose dans cet article en parallele avec les informations disponibles sur la salive des insectes phytophages broyeurs et des insectes hematophages.

Study of aphid saliva: a prerequisite to new bio-insecticides development. Aphids, major insect pests of forests, cereal, vegetable, fruit and ornamental crops, are controlled mainly by synthetic insecticides. However, due to the adverse effects of these ones on the environment and the development of resistant populations of aphids, it is essential to adopt alternative control. Aphid saliva plays a key role during insect feeding. It contains a wide variety of compounds whose specificity of action allows to dissect some physiological mechanisms that govern the interactions between the insect and its host. Some identified compounds were found to induce defences of their host and are therefore considered promising tools in the fight against insect pests. One of the possible strategies is based on research and recovery of substances found in aphid saliva. This approach has been developed especially in hematophagous insects such as mosquitoes. The current state of knowledge about aphid saliva is discussed in this article in parallel with saliva of chewing phytophagous and hematophagous insects.

Plant defensive strategies bring into play blends of compounds dependent on the type of attacker and coming from different synthesis pathways. Interest in the field is mainly focused on volatile organic compounds (VOCs) and jasmonic acid (JA). By contrast, little is known about the oxidized polyunsaturated fatty acids (PUFAs), such as PUFA-hydroperoxides, PUFA-hydroxides, or PUFA-ketones. PUFA-hydroperoxides and their derivatives might be involved in stress response and show antimicrobial activities. Hydroperoxides are also precursors of JA and some volatile compounds. In this paper, the differential biochemical response of a plant against insects with distinct feeding behaviours is characterized not only in terms of VOC signature and JA profile but also in terms of their precursors synthesized through the lipoxygenase (LOX)-pathway at the early stage of the plant response. For this purpose, two leading pests of potato with distinct feeding behaviours were used: the Colorado Potato Beetle (Leptinotarsa decemlineata Say), a chewing herbivore, and the Green Peach Aphid (Myzus persicae Sulzer), a piercing-sucking insect. The volatile signatures identified clearly differ in function with the feeding behaviour of the attacker and the aphid, which causes the smaller damages, triggers the emission of a higher number of volatiles. In addition, 9-LOX products, which are usually associated with defence against pathogens, were exclusively activated by aphid attack. Furthermore, a correlation between volatiles and JA accumulation and the evolution of their precursors was determined. Finally, the role of the insect itself on the plant response after insect infestation was highlighted.

Potato crops are facing too many pests, among which aphids are one of the most important. They are responsible for direct (phloem intake) and indirect damage the consequences of which are destructive: the injected saliva can be the vector of many pathogenic viruses. Intense use of aphicides has led to the selection of resistant aphid populations. As new chemical discovery and development are decreasing, few alternatives are available. Conscious of this problem, the scientific community is following a strategy consisting in developing biological control taking into account natural plant defences against aphids which have become multiresistant to insecticides. Conceivable strategies are presented and developed in this paper.

The role of insect saliva in the first contact between an insect and a plant is crucial during feeding. Some elicitors, particularly in insect regurgitants, have been identified as inducing plant defence reactions. Here, we focused on the salivary proteome of the green peach aphid, Myzus persicae. Proteins were either directly in-solution digested or were separated by 2D SDS-PAGE before trypsin digestion. Resulting peptides were then identified by mass spectrometry coupled with database investigations. A homemade database was constituted of expressed sequence tags from the pea aphid Acyrtosiphon pisum and M. persicae. The databases were used to identify proteins related to M. persicae with a nonsequenced genome. This procedure enabled us to discover glucose oxidase, glucose dehydrogenase, NADH dehydrogenase, alpha-glucosidase and alpha-amylase in M. persicae saliva. The presence of these enzymes is discussed in terms of plant-aphid interactions.

Potato crops are facing too many pests, among which aphids are one of the most important. They are responsible for direct (phloem intake) and indirect damage the consequences of which are destructive: the injected saliva can be the vector of many pathogenic viruses. Intense use of aphicides has led to the selection of resistant aphid populations. As new chemical discovery and development are decreasing, few alternatives are available. Conscious of this problem, the scientific community is following a strategy consisting in developing biological control taking into account natural plant defences against aphids which have become multiresistant to insecticides. Conceivable strategies are presented and developed in this paper.

Oxylipins are oxygenated fatty acids and their derivatives that play key roles in response to stress. They are widespread in many organisms including mammals or plants but are unknown in arthropods. In this study, we identified oxylipins in Myzys persicae Sulzer aphids reared on Vicia faba L. plants. Further experiments based on: (i) Radiolabelled substrate incubation with aphid extracts, and (ii) rearing of aphids on an artificial diet revealed that aphids were unable to synthesize oxylipins. As the V. faba total leaf oxylipin profile differs from the aphid one, it was assessed whether: (i) Aphids are able to transform leaf oxylipins, or (ii) phloem sap (ingested by aphids when feeding on plants) contains oxylipins different from total leaf ones. Phloem exudates analysis revealed, for the first time, that it contains oxylipins that are different from total leaf ones. These oxylipins are further ingested by aphids.

To cope with pathogen and insect attacks, plants develop different mechanisms of defence, in both direct (physical and chemical) and indirect ways (attractive volatiles to entomophagous beneficials). Plants are then able to express traits that facilitate “top‐down” control of pests by attracting herbivore predators. Here we investigate the indirect defence mechanism of potato plants by analyzing the volatile patterns of both healthy and aphid‐infested plants. Important changes in the emitted terpene pattern by the Myzus persicae infested host plant were observed. Using Solid Phase Micro Extraction (SPME) and GC‐MS, the ( E )‐β‐farnesene (EBF) appeared to be emitted by aphid‐infested potato and not by healthy plants. To assess the infochemical role of these volatile releases after aphid damage on the aphidophagous predators Episyrphus balteatus , the hoverfly foraging behavior was assessed using the Observer 5.0 software (Noldus, Wageningen, The Netherlands). Aphid‐free potato plants were also used as a control volatile source in the predator behavioral study. While aphid‐infested plants induced efficient searching and acceptation behaviors leading to egg‐laying, no kairomonal effect of healthy potato plants was observed, leading to longer immobility durations and shorter searching periods in the net cage. High oviposition rate of E. balteatus was observed when aphid‐infested potato was used (mean of 48.9 eggs per laying and per female). On the other hand, no egg was produced by the hoverfly on healthy aphid‐free plants. The E. balteatus foraging and reproductive behaviors according to the volatile emission from aphid‐infested plants are discussed in relation to the potential use of active infochemical molecules in integrated aphid pest management.

Chemical ecology is the study of how particular chemicals are involved in interactions of organisms with each other and with their surroundings. In order to reduce insect attack, plants have evolved a variety of defence mechanisms, both constitutive and inducible, while insects have evolved strategies to overcome these plant defences (such as detoxification enzymes). A major determinant of the influence of evolutionary arms races is the strategy of the insect: generalist insect herbivores, such as Myzus persicae aphid, need more complex adaptive mechanisms since they need to respond to a large array of different plant defensive chemicals. Here we studied the chemical ecology of M. persicae associated with different plant species, from Brassicaceae and Solanaceae families. To identify the involved adaptation systems to cope with the plant secondary substances and to assess the differential expression of these systems, a proteomic approach was developed. A non-restrictive approach was developed to identify all the potential adaptation systems toward the secondary metabolites from host plants. The complex protein mixtures were separated by two-dimensional electrophoresis methods and the related spots of proteins significantly varying were selected and identified by mass spectrometry (ESI MS/MS) coupled with data bank investigations. Fourteen aphid proteins were found to vary according to host plant switch; ten of them were down regulated (proteins involved in glycolysis, TCA cycle, protein and lipid synthesis) while four others were overexpressed (mainly related to the cytoskeleton). These techniques are very reliable to describe the proteome from organisms such as insects in response to particular environmental change such as host plant species of herbivores.