Abstract
BackgroundAphid attack induces defense responses in plants activating several signaling cascades that led to the production of toxic, repellent or antinutritive compounds and the consequent reorganization of the plant primary metabolism. Pepper (Capsicum annuum L.) leaf proteomic response against Myzus persicae (Sulzer) has been investigated and analyzed by LC-MS/MS coupled with bioinformatics tools.ResultsInfestation with an initially low density (20 aphids/plant) of aphids restricted to a single leaf taking advantage of clip cages resulted in 6 differentially expressed proteins relative to control leaves (3 proteins at 2 days post-infestation and 3 proteins at 4 days post-infestation). Conversely, when plants were infested with a high density of infestation (200 aphids/plant) 140 proteins resulted differentially expressed relative to control leaves (97 proteins at 2 days post-infestation, 112 proteins at 4 days post-infestation and 105 proteins at 7 days post-infestation). The majority of proteins altered by aphid attack were involved in photosynthesis and photorespiration, oxidative stress, translation, protein folding and degradation and amino acid metabolism. Other proteins identified were involved in lipid, carbohydrate and hormone metabolism, transcription, transport, energy production and cell organization. However proteins directly involved in defense were scarce and were mostly downregulated in response to aphids.ConclusionsThe unexpectedly very low number of regulated proteins found in the experiment with a low aphid density suggests an active mitigation of plant defensive response by aphids or alternatively an aphid strategy to remain undetected by the plant.Under a high density of aphids, pepper leaf proteome however changed significantly revealing nearly all routes of plant primary metabolism being altered. Photosynthesis was so far the process with the highest number of proteins being regulated by the presence of aphids.In general, at short times of infestation (2 days) most of the altered proteins were upregulated. However, at longer times of infestation (7 days) the protein downregulation prevailed.Proteins involved in plant defense and in hormone signaling were scarce and mostly downregulated.
Highlights
Aphid attack induces defense responses in plants activating several signaling cascades that led to the production of toxic, repellent or antinutritive compounds and the consequent reorganization of the plant primary metabolism
The central time point (4 dpi) was the one showing a higher number of regulated proteins (Fig. 2b), and it represents an intermediate situation in the proteomic response, with more or less equal number of proteins shared with the shorter (2 dpi) and longer (7 dpi) time of aphid infestation
LC-MS/MS analysis coupled with bioinformatics resulted to be a powerful approach to study pepper leaf proteome responses to M. persicae infestation
Summary
Aphid attack induces defense responses in plants activating several signaling cascades that led to the production of toxic, repellent or antinutritive compounds and the consequent reorganization of the plant primary metabolism. The signs and symptoms of aphid attack can be diverse (chlorosis, necrosis, wilting, stunting, and malformation of new growth), it is likely that host molecular response is specific for a certain plant-aphid interaction [6, 7] To their direct effects, aphid honeydew excrement can build enough on plants impairing photosynthesis and promoting the development of fungal diseases [4, 5] and aphids are vectors of plant viruses, transmitting nearly 30% of all plant virus species described to date [8]. Between all aphid species Myzus persicae (Sulzer), the green peach aphid, especially stands out for being highly polyphagous It feeds on over 400 plant species belonging to nearly 50 plant families, affecting several important agricultural and horticultural crops. The identification of factors that regulate plant resistance or tolerance and limit aphid infestation is momentousness
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