Project description:Transcriptional profiling of 3 day old virgin male and female adults comparing control male Drosophila melanogaster (MDM) versus male D sechellia (MDS) and comparing control female Drosophila melanogaster (FDM) versus female D sechellia (FDS). Goal was to determine why D sechellia is tolerant to octanoïc acid, the major toxic compound of Morinda citrifolia fruit
Project description:The dietary specialist fruit fly Drosophila sechellia evolved to feed primarily on the toxic fruit of Morinda citrifolia. Seeking the basis of adaptations to the unique chemistry of its host plant, we profiled genome-wide gene expression response to L-DOPA because it is highly abundant in M. citrifolia, critical for reproductive success of D. sechellia, and may influence toxin resistance in this species. Here we used a combination of functional genetics and genomics to identify a new gene, Esterase 6 (Est6) that is important for D. sechellia ecological adaptation to this new niche.
Project description:Drosophila sechellia is an island endemic host specialist that has evolved to consume the toxic fruit of Morinda citrifolia, also known as noni fruit. Recent studies by our group and others have examined genome-wide gene expression responses of fruit flies to individual highly abundant compounds found in noni responsible for the fruit’s unique chemistry and toxicity. In order to relate these reductionist experiments to the gene expression responses to feeding on noni fruit itself, we fed rotten noni fruit to adult female D. sechellia and performed RNA-sequencing. Combining the reductionist and more wholistic approaches, we have identified candidate genes that may contribute to each individual compound and those that play a more general role in response to the fruit as a whole. Using the compound specific and general responses, we used transcription factor prediction analyses to identify the regulatory networks and specific regulators involved in the responses to each compound and the fruit itself. The identified genes and regulators represent the possible genetic mechanisms and biochemical pathways that contribute to toxin resistance and noni specialization in D. sechellia.
Project description:The dietary specialist fruit fly Drosophila sechellia has evolved to specialize on the toxic fruit of its host plant Morinda citrifolia. Toxicity of Morinda fruit is primarily due to high levels of octanoic acid (OA). Using RNA interference (RNAi), prior work found that knockdown of Osiris family genes Osiris 6 (Osi6), Osi7, and Osi8 led to increased susceptibility to OA in adult D. melanogaster flies, likely representing genes underlying a Quantitative Trait Locus (QTL) for OA resistance in D. sechellia. While genes in this major effect locus are beginning to be revealed, prior work has shown at least five regions of the genome contribute to OA resistance. Here, we identify new candidate OA resistance genes by performing differential gene expression analysis using RNA sequencing (RNA-seq) on control and OA-exposed D. sechellia flies. We found 104 significantly differentially expressed genes with annotated orthologs in D. melanogaster, including six Osiris gene family members, consistent with previous functional studies and gene expression analyses. Gene ontology (GO) term enrichment showed significant enrichment for cuticle development in upregulated genes and significant enrichment of immune and defense responses in downregulated genes suggesting important aspects of the physiology of D. sechellia that may play a role in OA resistance. In addition, we identified 5 candidate OA resistance genes that potentially underlie QTL peaks outside of the major effect region, representing promising new candidate genes for future functional studies.
Project description:Here we show that Drosophila sechelliaM-bM-^@M-^Ta specialist on the fruit of Morinda citrifolia that recently diverged from its generalist sister-species, D. simulansM-bM-^@M-^Thas rapidly accumulated loss-of-function alleles and reduced gene expression at genes affecting olfaction, detoxification, and metabolism. While D. sechellia increases expression of genes involved with oogenesis and fatty acid metabolism when on its host, many more genes show reduced expression in D. sechellia. For several functionally related genes, this decrease in expression is associated with loss-of-function alleles. The rapid accumulation of these alleles potentially affected D. sechelliaM-bM-^@M-^Ys initial adaptation to M. citrifolia, likely contributes to D. sechelliaM-bM-^@M-^Ys poor competitive ability off of its host, and increases ecological isolation between D. sechellia and its sister species. Keywords: comparative hybridization, gene expression 2 species (simulans and sechella) by choice vs no-choice treatment for octanoic & hexanoic acid blend
Project description:Here we show that Drosophila sechellia—a specialist on the fruit of Morinda citrifolia that recently diverged from its generalist sister-species, D. simulans—has rapidly accumulated loss-of-function alleles and reduced gene expression at genes affecting olfaction, detoxification, and metabolism. While D. sechellia increases expression of genes involved with oogenesis and fatty acid metabolism when on its host, many more genes show reduced expression in D. sechellia. For several functionally related genes, this decrease in expression is associated with loss-of-function alleles. The rapid accumulation of these alleles potentially affected D. sechellia’s initial adaptation to M. citrifolia, likely contributes to D. sechellia’s poor competitive ability off of its host, and increases ecological isolation between D. sechellia and its sister species. Keywords: comparative hybridization, gene expression