LIPID-BODY LIPOXYGENASE IS EXPRESSED IN COTYLEDONS DURING GERMINATIONPRIOR TO OTHER LIPOXYGENASE FORMS

Lipid bodies are degraded during germination. Whereas some proteins, e .g. oleosins, are synthesized during the formation of lipid bodies of maturating seeds, a new set of proteins, including a specific form of lipoxygenase (LOX; EC 1.13.11.12), is detectable in lipid bodies durin g the stage of fat degradation in seed germination. In cotyledons of c ucumber (Cucumis sativus L.) seedlings at day 4 of germination, the mo st conspicuous staining with anti-LOX antibodies was observed in the c ytosol. At very early stages of germination, however, the LOX form pre sent in large amounts and synthesized preferentially was the lipid-bod y LOX. This was demonstrated by immunocytochemical staining of cotyled ons from 1-h and 24-h-old seedlings: the immunodecoration of sections of 24-h-old seedlings with anti-LOX antiserum showed label exclusively correlated with lipid bodies of around 3 mu m in diameter. In accorda nce, the profile of LOX protein isolated from lipid bodies during vari ous stages of germination showed a maximum at day 1. By measuring bios ynthesis of the protein in vivo we demonstrated that the highest rates of synthesis of lipid-body LOX occurred at day 1 of germination. The early and selective appearance of a LOX form associated with lipid bod ies at this stage of development is discussed.