Étude des réponses des insectes aux stress environnementaux par une approche protéomique.

by Nguyen, Thi Thuy

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 défensive value. Here, we examined (i) water deprivation and (ii) défoliation 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. continuously stressed potato for 14 days (no watering; défoliation maintained at -40%). Aphid performance under stress was correlated with metabolic responses monitored by profiling of the aphid proteome. Macrosiphum euphorbiae was strongly affected by water stress, as adult survival, total aphid number and biomass were reduced by 67%, 64% and 79% respectively. Aphids performed normally on defoliated potato, indicating that they were unaffected or able to compensate any stress induced by plant défoliation. Stressed aphid proteomes revealed 419-453 protein spots, including 27 that were modulated specifically or jointly under each kind of host plant stress. Reduced aphid fitness on water-stressed plants mostly correlated with modulation of proteins involved in energy metabolism, apparently to conserve energy in order to prioritize survival. Despite normal performance, several aphid proteins that are known to be implicated in cell communication were modulated on defoliated plants, possibly suggesting modified aphid behaviour. The GroEL protein (or symbionin) of the endosymbiont Buchnera aphidicola was prédominant under ail conditions in M. euphorbiae. Its expression level was not significantly affected by aphid host plant stresses, which is consistent with the high priority of symbiosis in stressed aphids.