The Drosophila foraging Gene Mediates Adult Plasticity and Gene–Environment Interactions in Behaviour, Metabolites, and Gene Expression in Response to Food Deprivation Clement F. Kent1, Tim Daskalchuk2, Lisa Cook2, Marla B. Sokolowski1*, Ralph J. Greenspan3 1 Department of Biology, University of Toronto Mississauga, Ontario, Canada, 2 Phenomenome Discoveries, Saskatoon, Saskatchewan, Canada, 3 The Neurosciences Institute, San Diego, California, United States of America Abstract Nutrition is known to interact with genotype in human metabolic syndromes, obesity, and diabetes, and also in Drosophila metabolism. Plasticity in metabolic responses, such as changes in body fat or blood sugar in response to changes in dietary alterations, may also be affected by genotype. Here we show that variants of the foraging (for) gene in Drosophila melanogaster affect the response to food deprivation in a large suite of adult phenotypes by measuring gene by environment interactions (GEI) in a suite of food-related traits. for affects body fat, carbohydrates, food-leaving behavior, metabolite, and gene expression levels in response to food deprivation. This results in broad patterns of metabolic, genomic, and behavioral gene by environment interactions (GEI), in part by interaction with the insulin signaling pathway. Our results show that a single gene that varies in nature can have far reaching effects on behavior and metabolism by acting through multiple other genes and pathways. Citation: Kent CF, Daskalchuk T, Cook L, Sokolowski MB, Greenspan RJ (2009) The Drosophila foraging Gene Mediates Adult Plasticity and Gene–Environment Interactions in Behaviour, Metabolites, and Gene Expression in Response to Food Deprivation. PLoS Genet 5(8): e1000609. doi:10.1371/journal.pgen.1000609 Editor: Greg Gibson, The University of Queensland, Australia Received February 3, 2009; Accepted July 20, 2009; Published August 21, 2009 Copyright: 2009 Kent et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This research was supported by Grant DK70141-2 from NIDDK (www.niddk.nih.gov) to MBS and by the Neurosciences Research Foundation (www.nsi. edu). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: marla.sokolowski@utoronto.ca Introduction The question of how phenotypic plasticity evolves has been the subject of vigorous debate (reviewed in [1,2,3]), as has the related question of whether allelic variation in single genes can have large impacts on plasticity [3]. Phenotypic plasticity is defined as the degree to which the environment can change or modify the phenotype. Genotype-environment interaction (GEI) is genetic variation in phenotypic plasticity. The genetic variation in GEI is needed for the evolution of an adaptive level of phenotypic plasticity [4]. Here we abbreviate ‘‘the phenotypic plasticity of one genotype in different environments’’ to ‘‘plasticity’’. Recent studies show that quantitative trait loci can have large effects on GEI [5] and that traits with GEI responses to nutrition can be correlated with GEI in the expression of a relatively small number of genes [6]. In this paper, we examine GEIs resulting from variation in a single gene, in response to food deprivation. We begin the process of determining the mechanism by which alleles of this gene affect plasticity. By quantifying the proportion of a large number of gene expression and metabolite traits in which the gene is involved in GEI, we also provide experimental data on the extent of the gene’s pleiotropy and its allelic contributions to plasticity. The foraging (for) gene of D. melanogaster encodes a cGMP dependent protein kinase [7,8]. Naturally occurring for alleles give rise to the rover and sitter behavioural morphs. As larvae, rovers move more and feed less in the presence of food than sitters, but don’t differ in locomotion in the absence of food [9,10,11]. Food deprivation causes larval rovers to behave more like sitters [12]. Like their larval counterparts, adult rovers and sitters also differ in food-related behaviours. The sucrose response of rovers in a proboscis extension assay is higher than in sitters and the patterns of walking after feeding on a sucrose drop in sitters exhibits higher turning rates than in rovers [13,14,15]. In the present study, we investigate the response of adult rovers and sitters to well-fed (Fed) and food deprived (FD) conditions. Through global profiling of gene expression and metabolites, we find that rovers have greater changes in gene expression profiles and metabolite levels in response to food deprivation than do sitters, and that the insulin pathway is required for this rover-sitter difference. Allelic variation in for also influences the allocation of energy stores to lipids as compared to carbohydrates in fed flies. We conclude that allelic variation in for has a major effect on multiple aspects of food-related plasticity and GEI. Results We performed behavioural assays and gene expression profiling on flies from natural rover (forR) and sitter (fors) strains and from a sitter mutant strain (fors2) generated on a rover (forR) genetic background [9,13]. We exposed these flies to well-fed (Fed) or food deprived conditions (FD) (see methods). To contain cost, metabolite profiling was limited to the forR and fors2 strains. PLoS Genetics | www.plosgenetics.org 1 August 2009 | Volume 5 | Issue 8 | e1000609