Tomato (Solanum lycopersicum) is a model plant for studying fleshy fruit development. Several genetic and molecular approaches have been developed to increase our knowledge about the physiological basis of fruit growth, but very few data are yet available at the proteomic level. The main stages of fruit development were first determined through the dynamics of fruit diameter and pericarp cell number. Then, total proteins were extracted from pericarp tissue at six relevant developmental stages and separated by two-dimensional gel electrophoresis. Protein patterns were markedly different between stages.Proteins showing major variations were monitored. We identified 90 of 1,791 well-resolved spots either by matrix-assisted laser-desorption ionization time-of-flight peptide mass fingerprinting or liquid chromatography-mass spectrometry sequencing and expressed sequence tag database searching. Clustered correlation analysis results pointed out groups of proteins with similar expression profiles during fruit development. In young fruit, spots linked to amino acid metabolism or protein synthesis were mainly expressed during the cell division stage and down-regulated later. Some spots linked to cell division processes could be identified. During the cell expansion phase, spots linked to photosynthesis and proteins linked to cell wall formation transiently increased. In contrast, the major part of the spots related to C compounds and carbohydrate metabolism or oxidative processes were up-regulated during fruit development, showing an increase in spot intensity during development and maximal abundance in mature fruit. This was also the case for spots linked to stress responses and fruit senescence. We discuss protein variations, taking into account their potential role during fruit growth and comparing our results with already known variations at mRNA and metabolite-profiling levels.

N-glycosylated proteins were isolated from Arabidopsis thaliana mature stems using affinity chromatography on Concanavalin A Sepharose, separated by 2D-electrophoresis and identified using nanoHPLC-MS/MS and MALDI-TOF MS. 102 glycoproteins were identified. 94% of these proteins were predicted by bioinformatics to be targeted to the secretory pathway and 87% of them were predicted to be localized in the cell wall or at the plasma membrane. 30% of these proteins belong to glycoside hydrolase (GH) families with some of them possibly involved in the hydrolysis of cell wall polysaccharides. The second major class of identified proteins comprises aspartyl and serine proteases. Other proteins are predicted to be oxido-reductases, contain interacting domains, are potentially involved in signalling or have an unknown function. This is, to our knowledge, the first survey of plant cell wall N-glycosylated proteins.

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