Comparison of autophagy in Bombyx mori midgut tissue under starvation condition and metamorphosis

Autophagy is a mechanism for cell survival under stress conditions such as starvation and plays a key role in the regulation and occurring of cell death. Midgut of silkworm, Bombyx mori, has been shown to be highly functional in larval stage but is partially degenerated by programmed cell death including autophagy during larval pupal metamorphosis. However, there are no studies on the similarities and differences between autophagy processes during metamorphosis and starvation conditions in the midgut. In this study, the biochemical and histological differences or similarities between programmed autophagy during metamorphosis and autophagy induced by starvation conditions in larval midgut of silkworm, Bombyx mori. For this purpose, larvae were starved on the 0th and 4th days of 5th instar. Total protein concentration was measured by Bradford assay in midgut obtained from starved larvae and the control group of metamorphosis occured and lysosomal enzymes acid phosphatase, cathepsin B and D were determined. Histological structure of midguts was examined using Hematoxylin & Eosin staining method. The results showed that, enzyme activities and protein degradation in autophagy leading to cell death during metamorphosis were much higher, also in autophagy which enables the survival of cells under starvation condition, enzyme activities and protein degradation have been shown to occur at lower levels.