Edited by Ulrike Heberlein, HHMI, Ashburn, VA, and approved July 23, 2018 (received for review September 26, 2017)
Quantifying the preference for particular foods is difficult in Drosophila because of the animal’s small meal size. It is common for fly feeding assays to induce or require starvation conditions. We have developed BARCODE, a method of tracking consumption preference by tagging foods with different oligonucleotides and later performing qPCR from the fly body to determine its feeding history. Because a fraction of the ingested oligomer persists for about a week, this assay provides a long-term record of the feeding pattern. We use this assay to study sexually dimorphic differences in ethanol consumption preference in Drosophila. BARCODE is also suitable for multiplex feeding studies in which the preference between more than two foods is simultaneously compared.
Drosophila melanogaster is a powerful model organism for dissecting the neurogenetic basis of appetitive and aversive behaviors. However, some methods used to assay food preference require or cause starvation. This can be problematic for fly ethanol research because it can be difficult to dissociate caloric preference for ethanol from pharmacological preference for the drug. We designed BARCODE, a starvation-independent assay that uses trace levels of oligonucleotide tags to differentially mark food types. In BARCODE, flies feed ad libitum, and relative food preference is monitored by qPCR of the oligonucleotides. Persistence of the ingested oligomers within the fly records the feeding history of the fly over several days. Using BARCODE, we identified a sexually dimorphic preference for ethanol. Females are attracted to ethanol-laden foods, whereas males avoid consuming it. Furthermore, genetically feminizing male mushroom body lobes induces preference for ethanol. In addition, we demonstrate that BARCODE can be used for multiplex diet measurements when animals are presented with more than two food choices.
Author contributions: A.P. and N.S.A. designed research; A.P. and T.T. performed research; A.P., T.T., and N.S.A. analyzed data; and A.P., T.T., and N.S.A. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1716880115/-/DCSupplemental.
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