The Maternal Origin of Acid Hydrolases in Drosophila and Their Relation with Yolk Degradation

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Abstract
The acid hydrolases of Drosophila are of maternal origin and appear subjected to differentiated control during embryogenesis. The enzymes are found associated with yolk granules. This association decreases during embryogenesis, in parallel with yolk degradation. As suggested before (Medina et al. Arch. Biochem. Biophys., 263, 355–363) the acid proteinase seems to be involved in the degradation of the yolk protein. The developmental profile of activity of the proteinase fits rather well with its involvement in the degradation of yolk granules. We have isolated intermediates of degradation of these subcellular structures. The intermediates have acid hydrolase activity and decrease in buoyant density during embryogenesis, in parallel with yolk degradation. The electron microscopic analysis has revealed that they are morphologically heterogenuous. A population of yolk granules appears to store mitochondria in their interior. The mitochondrial marker cytochrome oxidase is detected in density gradients associated with the intermediates of degradation, also supporting the storage of mitochondria in yolk granules in early development. The fact that the acid hydrolases are of maternal origin suggests that they have a role during embryogenesis. We propose that acid hydrolase(s) are involved in yolk degradation.