Pleiotropy of the Drosophila melanogaster foraging gene on larval feeding-related traits

Abstract

Little is known about the molecular underpinning of behavioral pleiotropy. The Drosophila melanogaster foraging gene is highly pleiotropic, affecting many independent larval and adult phenotypes. Included in foraging’s multiple phenotypes are larval foraging path length, triglyceride levels, and food intake. foraging has a complex structure with four promoters and 21 transcripts that encode nine protein isoforms of a cGMP dependent protein kinase (PKG). We examined if foraging’s complex molecular structure underlies the behavioral pleiotropy associated with this gene. Using a promotor analysis strategy, we cloned DNA fragments upstream of each of foraging’s transcription start sites and generated four separate for^pr-Gal4s. Supporting our hypothesis of modular function, they had discrete, restricted expression patterns throughout the larva. In the CNS, for^pr1-Gal4 and for^pr4-Gal4 were expressed in neurons while for^pr2-Gal4 and for^pr3-Gal4 were expressed in glia cells. In the gastric system, for^pr1-Gal4 and for^pr3-Gal4 were expressed in enteroendocrine cells of the midgut while for^pr2-Gal4 was expressed in the stem cells of the midgut. for^pr3-Gal4 was expressed in the midgut enterocytes, and midgut and hindgut visceral muscle. for^pr4-Gal4’s gastric system expression was restricted to the hindgut. We also found promoter specific expression in the larval fat body, salivary glands, and body muscle. The modularity of foraging’s molecular structure was also apparent in the phenotypic rescues. We rescued larval path length, triglyceride levels (bordered on significance), and food intake of for⁰ null larvae using different for^pr-Gal4s to drive UAS-for^cDNA. In a foraging null genetic background, for^pr1-Gal4 was the only promoter driven Gal4 to rescue larval path length, for^pr3-Gal4 altered triglyceride levels, and for^pr4-Gal4 rescued food intake. Our results refine the spatial expression responsible for foraging’s associated phenotypes, as well as the sub-regions of the locus responsible for their expression. foraging’s pleiotropy arises at least in part from the individual contributions of its four promoters.

Keywords:

• Drosophila melanogaster
• foraging gene
• pleiotropy
• multiple promoter analysis
• larval phenotypes

Acknowledgements

We would like to thank Jean-Christophe Billeter, and Joel Levine for guidance and advice as well as the Sokolowski Lab for helpful discussions. Megan Neville and Deniz Erezyilmaz for comments on the manuscript and two anonymous reviewers of this journal for helpful suggestions. Stocks obtained from the Bloomington Drosophila Stock Center (NIH P40OD018537) were used in this study.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research was supported by grants from the Natural Sciences and Engineering Council of Canada (NSERC), the Canadian Institutes for Health Research (CIHR) and NIDDK grant 5R01DK70141-2 to MBS.