We have investigated the mobilization of the main storage materials (proteins and lipids) present in the cotyledon cells of the olive seed during in vitro germination. For this purpose, a combination of cytological and biochemical methods has been used. In the mature embryo, seed storage proteins (SSPs) were accumulated in large, dense proteins bodies (PBs), surrounded by numerous, lipids storing oil bodies (OBs), filling up the cytoplasm. After seed imbibition, a gradual reduction in the pool of SSPs was detected by biochemical methods, which was accompanied by a decrease in the number of PBs, as a consequence of their fusion and by changes in the PBs matrix structure. Further mobilization of SSPs coincided with the transformation of several large PBs into a central vacuolar compartment with a few electro-dense inclusions inside its lumen, containing SSPs. The mobilization of lipids started after seed imbibition. At this time, a decrease in OBs number coincided with relatively high levels of lipoxygenase (LOX) activity. This enzyme was localized inside the PBs after immunocytochemistry. This localization, together with the close spatial relationship between OBs and the PBs boundary, suggests that PBs could be involved in the mobilization of lipids. We propose that PBs operate as multifunctional organelles. As germination proceeds, a strong decrease in both OBs number and LOX activity were observed simultaneously to the SSPs hydrolyses. All these cellular and biochemical changes strongly reflect an interconnected mobilization of storage proteins and lipids, which contributes to the differentiation process of the cotyledonary cells in the olive seed.

Resumen de la comunicación oral presentada en el XVII Congress of the Federation of European Societies of Plant Biology (FESPB), celebrado del 4 al 9 de Julio de 2010 en Valencia.-- P13-O19.

This work was supported by JA project (P06-AGR-01791) and the MICINN (project BFU2008-00629/BFI).

Peer reviewed