Abstract
Aging is the overall decline of cellular processes with time and recent work has shown that small RNA pathways are involved in aging in many ways. Small RNAs play important roles in development, cellular physiology, and innate immunity by inhibiting complementary RNAs with the aid of RNA induced silencing complexes (RISC) in RNA interference (RNAi). There are two RNAi pathways in the somatic tissue of Drosophila melanogaster: the microRNA (miRNA) pathway and the small interfering RNA (siRNA) pathway. Argonaute1 (Ago1) is the core component of the miRNA RISC while Argonaute2 (Ago2) is the core component of the siRNA RISC. siRNA silencing efficiency is increased by the stress response transcription factor Forkhead box O (FOXO). FOXO responds to many stress pathways that have important implications for aging and lifespan. In the siRNA pathway, FOXO regulates Ago2 and the upstream processing enzyme Dicer-2 which produces siRNAs, while the only known FOXO targets in the miRNA pathway include RISC components and no processing enzymes. Because of this asymmetry, we speculated that FOXO may be able to alter the contents of argonaute RISC and therefore the total small RNA landscape as well, particularly as animals age. Here, we used next generation sequencing to investigate changes in small RNA abundance and RISC loading with age in male and female Drosophila. To our knowledge, these are the first small RNA libraries from Ago1 and Ago2 RISC in female Drosophila and the only comparison of sequencing libraries between total small RNA and RISC loaded RNA. We also assessed how the loss of FOXO could affect the aging small RNA landscape. We found that the majority of small RNAs do not change with age. The landscape is largely resistant to loss of FOXO but the loading of a few small RNAs in RISC is changed.