Quantitative subproteomic analysis of germinating related changes in the scutellum oil bodies of Zea mays

Oil bodies (OBs) were purified from the scutellum of mature maize embryos and from embryos 2 days after imbibition and their associated proteins were extracted and separated by 2-DE. Eighteen proteins were shown to be differentially accumulated, thirteen showed a higher accumulation in mature scutellum and five were highly accumulated in the germinating scutellum. Proteins were identified using LC-MS/MS. Besides previously known oil body protein oleosin, other proteins were identified in this study. Among accumulated proteins during imbibition are prohibitin 2, stress-inducible membrane pore protein Tim17 and manganese superoxide dismutase. Among the proteins whose amount decreases during imbibition are cupin 2, two different protein disulfide isomerases, a triosephosphate isomerase, a class IV heat shock protein, the embryonic protein DC-8, the 60S ribosomal protein P0, a nucleoside-diphosphate kinase, and a rubber elongation factor protein. Some of the identified proteins were previously located in organelles other than oil bodies, suggesting that OBs may interact with these organelles. We also suggest that OBs may act as transient storage depots for proteins that are temporally in excess.