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Mi-1-mediated defense response to nematodes and aphid

ABSTRACT: A pair of nearly isogenic tomato (Solanum lycopersicum) lines were used. These are: Motelle (Mi/Mi), root-knot nematode resistant and Moneymaker (mi/mi) root-knot nematode susceptible. A potato aphid (red biotype), imported from France, was used for infestation. An equal volume of sterile 1% carboxymethyl cellulose in water was added to the cleaned nematodes to keep them in suspension. The inoculum, consisting of 75-100 J2s, was dispensed in 10 µl aliquots using a repeat pipetter. The inoculum was pipetted 2 mm beneath the root tips. Control seedlings were inoculated with 0.5% carboxymethyl cellulose. After the desired incubation time (24 h or 36 h), seedlings were taken out of the boxes and a few set aside to check nematode infection rate. In our hand, this system results in 50% infection rate. The rest of the seedlings were placed on a water-saturated filter paper and the roots aligned. About 1 cm of the infected root tip was excised with a blade and quickly frozen on a polycarbonate membrane-lined 50 mm diameter Petri dish floating on liquid nitrogen and stored at -80C. Plants were grown for 6 weeks in a growth chamber under 16 h light/8 h dark at 25C in UCMix/sand, irrigated with water or MiracleGroR solution, then moved to an insect growth room (25C) 4-6 days before aphid infestation. Individual tomato leaflets were infested with 30-40 mixed stages of the potato aphids using plastic leaf cages. Four leaflets and two plants of each genotype were infested. Two plants of each genotype were used as controls. After the desired infestation time (6, 12, 24 or 48 h), leaflets were excised from the plants with a blade and sprayed with 1% SDS to force aphids to remove their stylets from the leaf tissue. Aphids were carefully removed from the leaflets and quickly frozen in liquid nitrogen. Control leaflets were excised and sprayed with 1% SDS before freezing. Samples were stored at -80C. RNA was isolated using the hot phenol method. Keywords: Direct comparison

ORGANISM(S): Solanum tuberosum Solanum lycopersicum

PROVIDER: GSE8136 | GEO | 2007/09/01

SECONDARY ACCESSION(S): PRJNA101021

REPOSITORIES: GEO

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Project description: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. Pepper (Capsicum annuum L.) leaf proteomic response against Myzus persicae (Sulzer) has been investigated and analyzed by LC-MS/MS coupled with bioinformatics tools. Infestation 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. The 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.

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Mi-1-mediated defense response to nematodes and aphid

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