title: Transcriptional variation associated with cactus host plant adaptation in Drosophila mettleri populations.
abstract: Although the importance of host plant chemistry in plant-insect interactions is widely accepted, the genetic basis of adaptation to host plants is not well understood. Here, we investigate transcriptional changes associated with a host plant shift in Drosophila mettleri. While D. mettleri is distributed mainly throughout the Sonoran Desert where it specializes on columnar cacti (Carnegiea gigantea and Pachycereus pringleii), a population on Santa Catalina Island has shifted to chemically divergent coastal prickly pear cactus (Opuntia littoralis). We compared gene expression of larvae from the Sonoran Desert and Santa Catalina Island when reared on saguaro (C. gigantea), coastal prickly pear and laboratory food. Consistent with expectations based on the complexity and toxicity of cactus relative to laboratory food, within-population comparisons between larvae reared on these food sources revealed transcriptional differences in detoxification and other metabolic pathways. The majority of transcriptional differences between populations on the cactus hosts were independent of the rearing environment and included a disproportionate number of genes involved in processes relevant to host plant adaptation (e.g. detoxification, central metabolism and chemosensory pathways). Comparisons of transcriptional reaction norms between the two populations revealed extensive shared plasticity that likely allowed colonization of coastal prickly pear on Santa Catalina Island. We also found that while plasticity may have facilitated subsequent adaptive divergence in gene expression between populations, the majority of genes that differed in expression on the novel host were not transcriptionally plastic in the presumed ancestral state.
authors.affiliation: Biology Department, University of Colorado Colorado Springs, 1420 Austin Bluffs Parkway, Colorado Springs, CO, 80918, USA.
authors.forename: Kim
authors.initials: K
authors.lastname: Hoang
authors.affiliation: Department of Biological Sciences, University of Alabama in Huntsville, 301 Sparkman Drive, Huntsville, AL, 35899, USA.|HudsonAlpha Institute for Biotechnology, 601 Genome Way, Huntsville, AL, 35806, USA.
authors.forename: Luciano M
authors.initials: LM
authors.lastname: Matzkin
authors.affiliation: Biology Department, University of Colorado Colorado Springs, 1420 Austin Bluffs Parkway, Colorado Springs, CO, 80918, USA.
authors.forename: Jeremy M
authors.initials: JM
authors.lastname: Bono
mesh_terms: D000220:Adaptation, Biological / Q000235:genetics*; D000818:Animals; D001130:Arizona; D029421:Cactaceae; D002140:California; D004330:Drosophila / Q000235:genetics*; D017344:Genes, Insect; D005828:Genetics, Population; D007814:Larva; D017423:Sequence Analysis, RNA; D059467:Transcriptome
keywords: Baldwin effect and genetic assimilation; detoxification; gene expression; genetic accommodation; metabolism; plasticity