Project description:In the presence of environmental change, natural selection can shape the transcriptome. Under a scenario of environmental change, genotypes that are better able to modulate gene expression to maximize fitness will tend to be favored. Therefore, it is important to examine gene expression at the population level in order to distinguish random or neutral gene expression variation from the pattern produced by natural selection. This study investigates the natural variation in transcriptional response to a cactus host shift utilizing the mainland Sonora population of Drosophila mojavensis. Drosophila mojavensis is a cactophilic species composed of four cactus host populations endemic to the deserts of North America. Overall, the change in cactus host was associated with a significant reduction in larval viability, as well as the differential expression of 21% of the genome (3,109 genes). Among the genes identified were a set of genes previously known to be involved in xenobiotic metabolism, as well as genes involved in cellular energy production, oxidoreductase/carbohydrate metabolism, structural components and mRNA binding. Interestingly, of the 3,109 genes whose expression was affected by host use, there was a significant overrepresentation of genes that lacked an orthologous call to the D. melanogaster genome, suggesting the possibility of an accelerated rate of evolution in these genes. Of the genes with a significant cactus effect, the majority, 2,264 genes, did not exhibit a significant cactus-by-line interaction. This population level approach facilitated the identification of genes involved in past cactus host shifts. Dataset from Population transcriptomics of cactus host shifts in Drosophila mojavensis, Matzkin, LM. Molecular Ecology.
Project description:Understanding the genetic basis of adaptation to novel environments remains one of the major challenges confronting evolutionary biologists. While newly developed genomic approaches hold considerable promise for addressing this overall question, the relevant tools have not often been available in the most ecologically interesting organisms. Our study organism, Drosophila mojavensis, is a cactophilic Sonoran Desert endemic utilizing four different cactus hosts across its geographic range. Its well-known ecology makes it an attractive system in which to study the evolution of gene expression during adaptation. As a cactophile, D. mojavensis oviposits in the necrotic tissues of cacti, therefore exposing larvae and even adults to the varied and toxic compounds of rotting cacti. We have developed a cDNA microarray of D. mojavensis to examine gene expression associated with cactus host use. Using a population from the Baja California population we examined gene expression differences of third instar larvae when reared in two chemically distinct cactus hosts, agria (Stenocereus gummosus, native host) vs. organpipe (S. thurberi, alternative host). We have observed differential gene expression associated with cactus host use in genes involved in metabolism and detoxification. Keywords: host adaptation, stress response, detoxification