Search

A comparative proteomics study using isobaric tags for relative and absolute quantitation (iTRAQ) was performed on a mesophytic tomato (Solanum lycopersicum) cultivar and a dehydration-resistant wild species (Solanum chilense) to identify proteins that play key roles in tolerance to water deficit stress. In tomato ‘Walter’ LA3465, 130 proteins were identified, of which 104 (80%) were repressed and 26 (20%) were induced. In S. chilense LA1958, a total of 170 proteins were identified with 106 (62%) repressed and 64 (38%) induced. According to their putative molecular functions, the differentially expressed proteins belong to the following subgroups: stress proteins, gene expression, nascent protein processing, protein folding, protein degradation, carbohydrate metabolism, amino acid and nucleotide metabolism, lipid metabolism, signal transduction, and cell cycle regulation. Based on changes in protein abundance induced by the dehydration treatment, cellular metabolic activities and protein biosynthesis were suppressed by the stress. In S. chilense, dehydration treatment led to elevated accumulation of proteins involved in post-transcriptional gene regulation and fidelity in protein translation including prefoldin, which promotes protein folding without the use of adenosine-5′-triphosphate (ATP), several hydrophilic proteins, and calmodulin in the calcium signal transduction pathway. Those protein changes were not found in the susceptible tomato, ‘Walter’. Within each functional protein group, proteins showing opposite changes (dehydration induced vs. repressed) in the two species were identified and roles of those proteins in conferring tolerance to water deficit stress are discussed. Information provided in this report will be useful for selection of proteins or genes in analyzing or improving dehydration tolerance in tomato cultivars.

This article reports salt-induced changes in leaf and root proteomes after wild tomato (Solanum chilense) plants were treated with 200 mm NaCl. In leaf tissues, a total of 176 protein spots showed significant changes (P < 0.05), of which 104 spots were induced and 72 spots suppressed. Salt-induced proteins are associated with the following pathways: photosynthesis, carbohydrate metabolism, glyoxylate shunt, glycine cleavage system, branched-chain amino acid biosynthesis, protein folding, defense and cellular protection, signal transduction, ion transport, and antioxidant activities. Suppressed proteins belong to the following categories: oxidative phosphorylation pathway, photorespiration and protein translational machinery, oxidative stress, and ATPases. In root tissues, 106 protein spots changed significantly (P < 0.05) after the salt treatment, 63 spots were induced, and 43 suppressed by salt treatment. Salt-induced proteins are associated with the following functional pathways: regeneration of S-adenosyl methionine, protein folding, selective ion transport, antioxidants and defense mechanism, signal transduction and gene expression regulation, and branched-chain amino acid synthesis. Salt-suppressed proteins are receptor kinase proteins, peroxidases and germin-like proteins, malate dehydrogenase, and glycine dehydrogenase. In this study, different members of proteins were identified from leaf and root tissues after plants were subjected to salt treatment. These proteins represent tissue-specific changes in salt-induced proteomes. When protein expression was compared in the context of metabolic pathways, the branched-chain amino acid biosynthesis, glucose catabolism toward reducing cellular glucose level, and the antioxidant, detoxification, and selective ion uptake and transport were induced in both root and leaf tissues. These changes appear to be associated with salt tolerance in the whole plant.

Resistance to begomoviruses, including bipartite tomato mottle virus (ToMoV) and monopartite tomato yellow leaf curl virus (TYLCV), has been introgressed to cultivated tomato (Solanum lycopersicum) from Solanum chilense accessions LA1932 and LA2779. A major gene, Ty-3, responsible for resistance to ToMoV and TYLCV was previously mapped on the long arm of chromosome 6. In the present study, we identified a 14-cM S. chilense introgression on the long arm of chromosome 3 in some resistant breeding lines derived from LA1932. A new begomovirus resistance locus, Ty-4, was mapped to the 2.3-cM marker interval between C2_At4g17300 and C2_At5g60160 in the introgression. Analysis of a population segregating for Ty-3 and Ty-4 demonstrated that Ty-3 accounted for 59.6% of the variance, while Ty-4 only accounted for 15.7%, suggesting that Ty-4 confers a lesser effect on TYLCV resistance. Recombinant inbred lines (RILs) with Ty-3 and Ty-4 had the highest level of TYLCV resistance. The PCR-based markers tightly linked to the Ty-4 locus as well as the Ty-3 locus have been recently used in our breeding program for efficient selection of high-levels of begomovirus resistance and now allow for efficient breeding by marker-assisted selection.