Proteome analysis of embryo and endosperm from germinating tomato seeds

Proteome analysis of embryo and endosperm tissues from germinating tomato seed was conducted using 1-DE, 2-DE, and MS. Mobilization of the most abundant proteins, which showed similar profiles in the two tissues, occurred first in the endosperm. CBB R-250 staining of 2-DE gels revealed 352 and 369 major protein spots in the embryo and endosperm, respectively, at 0 h. Of these, 75 major spots were selected, excised, in-gel digested with trypsin, and analyzed by MALDI-TOF-MS and/or LC-ESI-Q/TOF-MS/MS. Peptide MS and MS/MS data were searched against publicly available protein and EST databases, and 47 proteins identified. Embryo-specific proteins included a BAC19.13 homologue, whereas four proteins specific to the endosperm were tomato mosaic virus coat proteins related to defense mechanisms. The most abundant proteins both in the embryo and endosperm were seed storage proteins, i.e., legumins (11 spots), vicilins (11 spots), albumin (2 spots). Housekeeping enzymes, actin-binding profilin, defense-related protein kinases, nonspecific lipid transfer protein, and proteins involved in general metabolism were also identified. The roles of some of the proteins identified in the embryo and endosperm are discussed in relation to seed germination in tomato.