Differential Gene Expression in Starvation Selected Drosophila Melanogaster
Fruit flies that have been selected for starvation resistance can be used in experimental studies to study physiological processes. Both their genomes and their phenotypes, especially metabolism, change significantly as a result of artificial selection. Starvation selected flies develop slower and are larger due to higher lipid content as adults. We used flies that have been selected for more than 138 generations. We used RNAseq study gene expression in third instar larval fat body tissue. This tissue is known to have many functions in Drosophila melanogaster and has been compared functionally to the human liver. We used third instar larvae from selected and control lines at the same chronological time point, 108±6 hours after egg laying. At this time point, the fed control (“FC”) lines were wandering, and the starvation selected (“SS”) lines were in the third larval instar but not yet wandering, due to longer larval feeding and delayed development.
DAVID and bioinformatic statistical analyses showed genes of interest that were significantly up- and down-regulated in each population. The level of regulation is reciprocally related between the fed control lines and starvation selected lines; i.e. an up-regulated gene in starvation selected lines is down-regulated in the fed control lines, and vice versa. The gene clusters that were most up-regulated in the starvation selected lines were glutathione metabolism, regulation of lipid storage, pseudouridine synthesis, mitochondrial proton transport, long-chain fatty acid biosynthesis, response to sucrose, and glycogen metabolism. The gene clusters that were most down-regulated in the starvation selected lines were the proteasome, pyruvate metabolism, the TCA cycle, and malate metabolism. We conclude that third instar larvae in the SS and FC populations have significantly different transcriptomes. Analysis of candidate genes responsible for these differences can inform cause and effect.