Project description:In this study, we utilized Comparative Genomic Hybridization (CGH), using probes designed from EST sequence, to identify genes located on the X chromosome of four species in the stalk-eyed fly genus Teleopsis. Analysis of log ratio values from the CGH microarrays for over 3400 genes produces a strongly bimodal distribution that clearly differentiates autosomal from X-linked genes for all four species. Genetic mapping of 35 of these genes in T. dalmanni indicates the CGH results correctly identified chromosomal location in all cases. Syntenic comparison with Drosophila indicates that 90% of the X-linked genes in Teleopsis are homologous to genes located on chromosome 2L in D. melanogaster, suggesting the formation of a nearly complete neo-X chromosome from Muller element B in the Dipteran lineage leading to Teleopsis. Overall, this study demonstrates CGH is a useful technique for identifying chromosomal sex-linkage and should be applicable to other organisms with EST or partial genomic information.
Project description:In this study, we utilized Comparative Genomic Hybridization (CGH), using probes designed from EST sequence, to identify genes located on the X chromosome of four species in the stalk-eyed fly genus Teleopsis. Analysis of log ratio values from the CGH microarrays for over 3400 genes produces a strongly bimodal distribution that clearly differentiates autosomal from X-linked genes for all four species. Genetic mapping of 35 of these genes in T. dalmanni indicates the CGH results correctly identified chromosomal location in all cases. Syntenic comparison with Drosophila indicates that 90% of the X-linked genes in Teleopsis are homologous to genes located on chromosome 2L in D. melanogaster, suggesting the formation of a nearly complete neo-X chromosome from Muller element B in the Dipteran lineage leading to Teleopsis. Overall, this study demonstrates CGH is a useful technique for identifying chromosomal sex-linkage and should be applicable to other organisms with EST or partial genomic information. Two-condition experiment, female vs. male DNA, for four species, each with 4 biological replicates
Project description:We utilized Comparative Genomic Hybridization (CGH), using probes designed from de novo assembly of 10 tissues into a grand transcriptome to identify genes located on the X and Y chromosomes of a stalk-eyed fly, Teleopsis dalmanni. We use next generation sequencing of RNA to identify over 500 genes that are differentially expressed in the testes due to the effects of a driving X chromosome (XSR) in T. dalmanni. Most of these genes were X-linked, evolving more rapidly than control genes, and exhibit elevated expression in the gonads. Finally, XSR has become genetically differentiated from standard X chromosomes – using the RNA sequence data, we found nearly 1000 sites in X-linked genes and only a handful in autosomal genes where there was a fixed nucleotide difference. We conclude that XSR has led to widespread sequence and expression divergence on the X chromosome in T. dalmanni.
Project description:We utilized Comparative Genomic Hybridization (CGH), using probes designed from de novo assembly of 10 tissues into a grand transcriptome to identify genes located on the X and Y chromosomes of a stalk-eyed fly, Teleopsis dalmanni. We use next generation sequencing of RNA to identify over 500 genes that are differentially expressed in the testes due to the effects of a driving X chromosome (XSR) in T. dalmanni. Most of these genes were X-linked, evolving more rapidly than control genes, and exhibit elevated expression in the gonads. Finally, XSR has become genetically differentiated from standard X chromosomes M-bM-^@M-^S using the RNA sequence data, we found nearly 1000 sites in X-linked genes and only a handful in autosomal genes where there was a fixed nucleotide difference. We conclude that XSR has led to widespread sequence and expression divergence on the X chromosome in T. dalmanni. Two-condition experiment, female vs. male DNA, for one species with 4 biological replicates
Project description:BackgroundStalk-eyed flies of the family Diopsidae have proven to be an excellent model organism for studying the evolution of ornamental sexual traits. In diopsid flies the eyes and antennae are borne at the end of lateral head projections called 'eye-stalks'. Eyespan, the distance between the eyes, and the degree of sexual dimorphism in eyespan vary considerably between species and several sexually dimorphic species show sexual selection through female mate preference for males with exaggerated eyespan. Relatively little is known about the molecular genetic basis of intra- or inter-species variation in eyespan, eye-stalk development or growth regulation in diopsids. Molecular approaches including comparative developmental analyses, EST screening and QTL mapping have identified potential candidate loci for eyespan regulation in the model species Teleopsis dalmanni. Functional analyses of these genes to confirm and fully characterise their roles in eye-stalk growth require the development of techniques such as germline transformation to manipulate gene activity in vivo.ResultsWe used in vivo excision assays to identify transposon vector systems with the activity required to mediate transgenesis in T. dalmanni. Mariner based vectors showed no detectable excision while both Minos and piggyBac were active in stalk-eyed fly embryos. Germline transformation with an overall efficiency of 4% was achieved using a Minos based vector and the 3xP3-EGFP marker construct. Chromosomal insertion of constructs was confirmed by Southern blot analysis. Both autosomal and X-linked inserts were recovered. A homozygous stock, established from one of the X-linked inserts, has maintained stable expression for eight generations.ConclusionsWe have performed stable germline transformation of a stalk-eyed fly, T. dalmanni. This is the first transgenic protocol to be developed in an insect species that exhibits an exaggerated male sexual trait. Transgenesis will enable the development of a range of techniques for analysing gene function in this species and so provide insight into the mechanisms underlying the development of a morphological trait subject to sexual selection. Our X-linked insertion line will permit the sex of live larvae to be determined. This will greatly facilitate the identification of genes which are differentially expressed during eye-stalk development in males and females.