Project description:Local adaptation can play a fundamental role in the isolation of populations. While less well-studied than differentiation in sequence variation, changes in transcriptional variation during speciation also are fundamental to the evolutionary process. Drosophila mojavensis offers an unprecedented opportunity to examine the role of transcriptional differentiation in local adaptation. Drosophila mojavensis is a cactophilic fly composed of four ecologically distinct subspecies that inhabit the deserts of western North America. Each of the four subspecies utilizes necrotic tissue of different cactus host species characterized by distinct chemical profiles. The subspecies in Baja California, Mexico uses Stenocereus gummosus (Agria), in mainland Sonora it uses S. thurberi (Organ Pipe), in the Mojave Desert the host is Ferocactus cylindraceus (Red Barrel) and in Santa Catalina Island, USA, Opuntia littoralis (Prickly Pear) is the host. In this chapter we examine how the adaptation to the different environmental conditions across the four subspecies have shaped their transcriptional profiles. Using complete D. mojavensis genome microarrays we examined the transcriptome of third instar larvae from all four subspecies reared in standard laboratory media free of necrotic cactus-derived compounds. This experimental strategy focused on differences between constitutively expressed genes and not genes induced by necrotic cactus-derived compounds. The subspecies exhibited significant differential expression of genes that likely underlie the adaptation to different cactus hosts, such as detoxification genes (Glutathione S-transferases, Cytochrome P450s and UDP-Glycosyltransferases) and chemosensory genes (Odorant Receptors, Gustatory Receptors and Odorant Binding Proteins). Dataset from Matzkin, L. M. and Markow, T.A. Transcriptional differentiation across the four cactus host races of Drosophila mojavensis. In Speciation: Natural Processes, Genetics and Biodiversity. Edited by Michalak, P. Nova Science Publishers, Inc.

Project description:In Drosophila, adaptation to xeric environments presents many challenges, greatest among them the maintenance of water balance. Drosophila mojavensis, a cactophilic species from the deserts of North America, is one of the most desiccation-resistant in the genus, surviving low humidity primarily by reducing its metabolic rate. Genetic control of reduced metabolic rate, however, has yet to be elucidated. We utilized the recently sequenced genome of D. mojavensis to create an oligonucleotide microarray in order to pursue the identities of the genes involved in metabolic regulation during desiccation. We observed large differences in gene expression between male and female D. mojavensis as well as both quantitative and qualitative sex differences in their ability to survive xeric conditions. As expected, genes associated with metabolic regulation and carbohydrate metabolism were differentially regulated between stress treatments. Most importantly, we identified four points in central metabolism (Glyceraldehyde 3-phosphate dehydrogenase, transaldolase, alcohol dehydrogenase and phosphoenolpyruvate carboxykinase) that indicate the potential mechanisms controlling metabolic rate reduction associated with desiccation resistance. Furthermore, a large number of genes associated with vision pathways also were differentially expressed between stress treatments, especially in females, that may underlie the initial detection of stressful environments and trigger subsequent metabolic changes. Dataset from Transcriptional regulation of metabolism associated with the increased desiccation resistance of the cactophilic Drosophila mojavensis Matzkin,LM and Markow, MA, Genetics. The stock used in this study (15081-1352.22) was the same one utilized for the recently published D. mojavensis genome sequence. Flies were reared using standard Tucson Drosophila Stock Center banana/Opuntia media. The experimental design consisted of two mating status treatments (virgin and mated) and two stress treatments (desiccation and food) for both sexes. There were two replicates per mating status/stress/sex treatment (16 total hybridizations)

Project description:In internally fertilizing organisms, mating involves a series of highly coordinated molecular interactions between the sexes that occur within the female reproductive tract. In species with promiscuous mating systems, traits involved in postcopulatory interactions are expected to evolve rapidly, potentially leading to postmating-prezygotic (PMPZ) reproductive isolation between diverging populations. Here, we use a novel study design to investigate the postmating transcriptional response of Drosophila mojavensis female reproductive tracts following copulation with either conspecific or heterospecific (D. arizonae) males at three time points postmating. Relatively few genes (15 total) were transcriptionally regulated in the female lower reproductive tract in response to conspecific mating. Heterospecifically-mated females exhibited significant perturbations in the expression of the majority of these genes, and also downregulated transcription of a number of others, including several involved in mitochondrial function. These striking regulatory differences indicate failed postcopulatory molecular interactions between the sexes consistent with the strong PMPZ isolation observed for this cross. We also report, for the first time, the transfer of male mRNA transcripts to females during copulation. These included transcripts from male accessory-gland proteins (ACPs), a finding with potentially broad implications for understanding postcopulatory molecular interactions between the sexes. Dataset from Postmating transcriptional changes in reproductive tracts of con- and heterospecifically-mated Drosophila mojavensis females Bono, JM, Matzkin,LM, Kelleher, ES, and Markow, MA, Proceedings of the National Academy of Sciences, USA. The treatments were con- and heterospecific mated D. mojavensis females. Three different post-copulation times points were assayed, 15 minutes, 2 hours and 6 hours. For each time point there were two independent replicates. Additionally, two replicates of a virgin D. mojavensis female control were assayed. A total of 14 arrays. All RNA extractions were from the lower reproductive tract of females.

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Drosophila mojavensis

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