The same oleosin isoforms are present in oil bodies of rice embryo and aleurone layer while caleosin exists only in those of the embryo

Oil bodies of similar sizes were observed in the cells of embryo and aleurone layer of rice seeds, and remained their structural integrity in vitro after isolation. Comparably, two abundant oleosin isoforms were found in both preparations of oil bodies isolated from the embryo and the aleurone layer. Immunological detection and mass spectrometric analyses indicated that the two oleosin isoforms, termed oleosin-H and oleosin-L, in the embryo and those in the aleurone layer were identical proteins encoded by the same genes (BAF12898.1 and BAF15387.1 for oleosin-H and oleosin-L, respectively). In contrast, one caleosin was found in oil bodies isolated from the embryo but not those isolated from the aleurone layer. Immunological staining of rice seeds confirms that oleosin is present in both embryo and aleurone layer while caleosin exists only in embryo. Caleosin extracted from oil bodies of rice embryo migrated faster on SDS-PAGE in the presence of Ca2+, in a manner identical to caleosin extracted from sesame oil bodies. Similar to other known monocot caleosins, the rice caleosin possesses an N-terminal appendix that is absent in dicotyledonous caleosins.