TEM Analysis of Autophagy in Drosophila melanogaster Fat Body Throughout the Progression of Metamorphosis

Abstract

Autophagy, the catabolic mechanism whereby stored nutrients are recycled, and the breakdown of problematic proteins and organelles within a cell, is an essential process necessary for maintenance of cellular homeostasis. When this process is misregulated, many physiological consequences ensue (Jing and Lim, 2012). Regulatory mechanisms of autophagy need to be further elucidated upon in order to be better understood.

During Drosophila larval development, the animal needs a constant supply of nutrients. A storage organ similar to mammalian adipose tissue and liver is the Drosophila fat body. When the animal intakes nutrients, insulin signaling is up regulated and nutrients are stored. Otherwise, when the animal undergoes a period of starvation as during metamorphosis, high titer pulses of 20-hydroxyecdysone (20E or ecdysone) induce autophagy in fat body cells to release nutrients. This allows for the animal’s other bodily cells to uptake the released amino and fatty acids from fat body, to survive and persist into the adult (Scott et al., 2004).

I am documenting the occurrence of autophagy throughout 7 time points of metamorphosis in wild-type (w1118) Drosophila melanogaster through utilizing transmission electron microscopy (TEM). TEM allows for the accurate visual detection of autolysosomes, but not the quantification of these autophagic structures. As expected, autolysosomes were present at 0, 2, 4, 6, 8, 10, and 12 hours after puparium formation (h APF), throughout metamorphosis.