title: Global Transcriptional Profiling of Diapause and Climatic Adaptation in Drosophila melanogaster.
abstract: Wild populations of the model organism Drosophila melanogaster experience highly heterogeneous environments over broad geographical ranges as well as over seasonal and annual timescales. Diapause is a primary adaptation to environmental heterogeneity, and in D. melanogaster the propensity to enter diapause varies predictably with latitude and season. Here we performed global transcriptomic profiling of naturally occurring variation in diapause expression elicited by short day photoperiod and moderately low temperature in two tissue types associated with neuroendocrine and endocrine signaling, heads, and ovaries. We show that diapause in D. melanogaster is an actively regulated phenotype at the transcriptional level, suggesting that diapause is not a simple physiological or reproductive quiescence. Differentially expressed genes and pathways are highly distinct in heads and ovaries, demonstrating that the diapause response is not uniform throughout the soma and suggesting that it may be comprised of functional modules associated with specific tissues. Genes downregulated in heads of diapausing flies are significantly enriched for clinally varying single nucleotide polymorphism (SNPs) and seasonally oscillating SNPs, consistent with the hypothesis that diapause is a driving phenotype of climatic adaptation. We also show that chromosome location-based coregulation of gene expression is present in the transcriptional regulation of diapause. Taken together, these results demonstrate that diapause is a complex phenotype actively regulated in multiple tissues, and support the hypothesis that natural variation in diapause propensity underlies adaptation to spatially and temporally varying selective pressures.
authors.affiliation: Department of Biology, University of Pennsylvania xiaqing@sas.upenn.edu.
authors.forename: Xiaqing
authors.initials: X
authors.lastname: Zhao
authors.affiliation: Department of Biology, Stanford University.
authors.forename: Alan O
authors.initials: AO
authors.lastname: Bergland
authors.affiliation: Department of Biology, University of Pennsylvania.
authors.forename: Emily L
authors.initials: EL
authors.lastname: Behrman
authors.affiliation: Department of Biology, University of Pennsylvania.
authors.forename: Brian D
authors.initials: BD
authors.lastname: Gregory
authors.affiliation: Department of Biology, Stanford University.
authors.forename: Dmitri A
authors.initials: DA
authors.lastname: Petrov
authors.affiliation: Department of Biology, University of Pennsylvania.
authors.forename: Paul S
authors.initials: PS
authors.lastname: Schmidt
mesh_terms: D000220:Adaptation, Biological / Q000235:genetics*; D000818:Animals; D002874:Chromosome Mapping; D002980:Climate; D019295:Computational Biology / Q000379:methods; D064666:Diapause, Insect / Q000235:genetics*; D004331:Drosophila melanogaster / Q000235:genetics*; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D063990:Gene Ontology; D059647:Gene-Environment Interaction; D058977:Molecular Sequence Annotation; D012621:Seasons; D059467:Transcriptome
keywords: Drosophila melanogaster; RNAseq; climatic adaptation; diapause