Proteomics research on the effects of applying selenium to apple leaves on photosynthesis

Untreated and Se-enriched apple leaves (Malus domestica Borkh. cv. 'Red Fuji') were used as the experimental materials. Proteomes of the differentially prepared tissues were compared through two-dimensional electrophoresis analysis and mass spectrum identification. There were 505 more protein spots in the proteome of the Se-enriched leaves than in the control leaves. Forty-seven protein spots were significantly differentially expressed (P < 0.05), among those, 32 protein spots were up-regulated while 12 protein points were down-regulated, and three new protein spots were found with the relative molecular masses of 31, 29, 26 kDa. Twenty-three protein spots with good shape and significant expression were selected for mass spectrometry analysis. These spots were excised from the gel and analyzed by a matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS). Peptide mass fingerprints (PMF) of all the proteins were submitted to NCBInr for protein identification, and 10 differential proteins were positively identified. Biological information of the identified proteins was found via http://www.uniprot.org/. There were three (1475, 1479, 1527) ribulose-1,5-bisphosphate carboxylase/oxygenase large subunits (Rubisco), two ribulose-1,5-bisphosphate carboxylases (346, 486) belonging to the Rubisco large chain family, one photosystem I reaction center subunit II (297), one chloroplast oxygen-evolving enhancer protein 1 (619), one Os12g0127100 protein whose function was unknown (927), one monodehydroascorbate reductase (1451), and one polyphenol oxidase V (1596). The major subcellular location for these proteins was the chloroplast, and they play important roles in photosynthesis and stress resistance for plants.