Enzymatic machinery involved in oil body breakdown during early pollen germination in the olive

Abstract

In many plants, pollen grains accumulate storage lipids that serve as energy supply during germination. In this work, we have characterized three enzymes (lipase, phospholipase A and lipoxygenase) involved in the early stages of oil body mobilization during olive pollen germination in vitro. In-gel assays showed the presence up to 12 putative lipases in germinated pollen. A single lipolytic band was also associated with oil bodies in the mature and germinated pollen. Early steps of pollen germination were also accompanied by lipoxygenase (LOX) activity. A protein of about 99 kDa with LOX activity was also detected in oil bodies isolated from germinated pollen. Moreover, oil bodies showed phospholipase A, lipase and LOX activities on their surface. Pollen germination was significantly hampered when specific inhibitors of the three enzymes were added to the germination medium or the stigmatic surface. All together, these data support the idea that these enzymes are involved in first steps of oil bodies' breakdown during pollen germination and that this process is essential for proper pollen performance.