Project description:Background: Stalk-eyed flies (family Diopsidae) are a model system for studying sexual selection due to the presence of elongated and sexually dimorphic eye-stalks in many species. Recent genomic studies on these flies have revealed a neo-X chromosome and evidence of gene movement onto or off of this X chromosome. To determine if sex linkage and gene movement are related to sexual dimorphism and sexual conflict, we compared gene expression between males and females using oligonucleotide microarrays and RNA from either developing eyestalk tissue or adult heads from a dimorphic species, Teleopsis dalmanni, or from developing eyestalk tissue in a congeneric monomorphic species, T. quinqueguttata. Results: Comparison of gene expression between the sexes for 3,748 genes indicates that dosage compensation is present due to elevated expression of X-linked genes in males. However, sex-biased expression was detected in 26% of the genes present in eye-antennal imaginal discs of larval T. dalmanni. Functional annotation reveals that female-biased genes are associated with transcription, anatomical development and cell communication in the nucleus, while male-biased genes are associated with metabolism and the mitochondria. Comparison of gene expression between experiments identified 140 genes with concordant sex-biased expression in the larval and adult tissues of T. dalmanni and 17 genes with identical sex-biased expression between species. There were only five reversals of sex-biased expression across experiments. In T. dalmanni, male-biased genes are more common on autosomes than on the X while female-biased genes are more common on the X in T. quinqueguttata. Female-biased expression is especially common among genes that moved onto the ancestral X while male-biased expression is more common among genes that moved onto an autosome. Conclusions: Genes with sex-biased expression exhibit different functions in each sex as expected if sexual conflict has influenced their evolution. The strong relationship between sex-biased expression and gene movement found in this study is consistent with resolution of sexual conflict by an RNA- or DNA-mediated process that moves genes between chromosomes. Measurement of gene expression in additional species should provide a more complete picture of how gene expression change occurs over evolutionary time in these extraordinary flies. Two-condition experiment, female vs. male RNA using larval eye discs for two species (Teleopsis dalmanni, Teleopsis quinqueguttata), and adult heads for one species (Teleopsis dalmanni).

Project description:Background: The horn fly, Haematobia irritans (L.), is an obligate blood-feeding parasite of cattle and control of this pest is a continuing problem in the United States and other parts of the world. Worldwide annual economic losses attributable to this pest surpass $1 billion. The fly is becoming resistant to pesticides and new control technologies are needed by cattle producers. Results: Dominant conditional lethal gene systems are being investigated as population control technologies against agricultural insect pests. One of the critical components of these systems is a highly expressed female-specific gene promoter which can be used to drive expression of a lethality-inducing gene. To identify candidate genes to supply this gene promoter, microarrays were designed from a recently developed horn fly EST database and probed to identify female-specific and larval-specific differential gene expression. Analysis of dyeswap experiments found 432 and 417 transcripts which were over- and under-expressed in adult female flies, respectively, compared to adult male flies. Additionally, 419 and 871 transcripts were over- and under-expressed in first instar larvae compared to adult flies. Three transcripts were identified which were over-expressed in adult females flies compared to adult males and which also were over-expressed in the first instar larval lifestage compared to adult flies. Conclusion: We have identified 3 strong candidates for further evaluation as a gene promoter source for the development of a female-specific conditional lethality system in the horn fly. One of these candidates, the putative nanos orthologue, has a high female-to-male expression ratio, has a moderate expression level in first instar larvae, and has been well characterized in D. melanogaster. Further investigations leading from this microarray analysis will include transformation of the horn fly and evaluation of the female conditional lethal system components for applicability to the specific biological parameters of natural populations of the horn fly. Keywords: evaluation of 1st instar larvae genes vs pooled adult + egg genes

Project description:Background: The horn fly, Haematobia irritans (L.), is an obligate blood-feeding parasite of cattle and control of this pest is a continuing problem in the United States and other parts of the world. Worldwide annual economic losses attributable to this pest surpass $1 billion. The fly is becoming resistant to pesticides and new control technologies are needed by cattle producers. Results: Dominant conditional lethal gene systems are being investigated as population control technologies against agricultural insect pests. One of the critical components of these systems is a highly expressed female-specific gene promoter which can be used to drive expression of a lethality-inducing gene. To identify candidate genes to supply this gene promoter, microarrays were designed from a recently developed horn fly EST database and probed to identify female-specific and larval-specific differential gene expression. Analysis of dyeswap experiments found 432 and 417 transcripts which were over- and under-expressed in adult female flies, respectively, compared to adult male flies. Additionally, 419 and 871 transcripts were over- and under-expressed in first instar larvae compared to adult flies. Three transcripts were identified which were over-expressed in adult females flies compared to adult males and which also were over-expressed in the first instar larval lifestage compared to adult flies. Conclusion: We have identified 3 strong candidates for further evaluation as a gene promoter source for the development of a female-specific conditional lethality system in the horn fly. One of these candidates, the putative nanos orthologue, has a high female-to-male expression ratio, has a moderate expression level in first instar larvae, and has been well characterized in D. melanogaster. Further investigations leading from this microarray analysis will include transformation of the horn fly and evaluation of the female conditional lethal system components for applicability to the specific biological parameters of natural populations of the horn fly. Keywords: adult male vs female hornfly gene expression

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Sex-biased gene expression in Drosophila melanogaster larvae

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