Proteomic analysis of the development and germination of date palm (Phoenix dactylifera L.) zygotic embryos

By using a comparative proteomic approach (2-DE coupled to MS/MS), the development, maturation, and germination of date palm zygotic embryos, have been studied. Proteins were trichloroacetic acid (TCA)-acetone-phenol extracted and resolved by 2-DE in the 5-8 pH range. The total protein content and the number of spots resolved increased from early (12 weeks after pollination (WAP); 68.96 mg/g DW 207 spots) to late (17 WAP; 240.85 mg/g DW 261 spots) stages, decreasing upon germination (from 120.8 mg/g DW 273 spots in mature embryos to 26.35 mg/g DW 87 spots in 15 days after germination). Up to 194 spots showed qualitative or quantitative differences between stages. Statistical analysis of spot variation was performed by PCA, obtaining a more accurate grouping of the samples and determining the most discriminant spots. Samples were also clustered based on Pearson distance and Ward's minimum distance. Sixty-five variable spots were subjected to MS analysis, resulting in 21 identifications. The identified proteins belong to the following functional categories: enzymes of glycolysis, tricarboxylic acid cycle, and carbohydrate biosynthesis, protein translation, storage (glutelin), and stress-related proteins. The evolution pattern of the functional groups was examined and discussed in terms of metabolism adaptation to the different embryogenic and germination stages.