Project description:An analysis of the transcriptional profiles of weak genetic perturbations generated via P-elements measured as heterozygotes in wing imaginal discs of Drosophila melanogaster. Abstract: A major objective of genomics is to elucidate the mapping between genotypic and phenotypic space as a step toward understanding how small changes in gene function can lead to elaborate phenotypic changes. One approach that has been utilized is to examine overall patterns of co-variation between phenotypic variables of interest, such as morphology, physiology and behavior, and underlying aspects of gene activity, in particular transcript abundance on a genome wide scale. Numerous studies have demonstrated that such patterns of co-variation occur, although these are often between samples with large numbers of unknown genetic differences (different strains, or even species) or perturbations of large effect (sexual dimorphism, or strong loss of function mutations), that may represent physiological changes outside of the normal experiences of the organism. We used weak mutational perturbations in genes affecting wing development in Drosophila melanogaster, that influence wing shape relative to a co-isogenic wild-type. We profiled transcription of 1150 genes expressed during wing development in 27 heterozygous mutants, as well as their co-isogenic wild type and one additional wild-type strain. Despite finding clear evidence of expression differences between mutants and wild-type, transcriptional profiles did not co-vary strongly with shape, suggesting that information from transcriptional profiling may not generally be predictive of final phenotype. We discuss these results in the light of possible attractor states of gene expression, and how this would affect interpretation of co-variation between transcriptional profiles and other phenotypes. Total RNA was extracted from pools of wing imaginal discs for each mutant strain as well as for their co-isogenic wild-type, and one additional wild-type strain. RNA was extracted using a modified protocol using the Qiagen RNAeasy kit.

Project description:In the eastern United States the buckeye butterfly, Junonia coenia, shows a seasonal wing color polyphenism where adults emerging in the spring are pale brown, while those emerging in the autumn are dark red. This variation can be artificially induced in laboratory colonies, thus making J. coenia a useful model system to examine the developmental basis of phenotypic plasticity. We used RNA-seq to generate the first set of assembled transcripts for this species while simultaneously quantifying relative gene expression associated with development of alternative seasonal color morphs. The assembled consolidated wing transcriptome was 77.55 Mb. 16,251 contigs of over 1000bp in length were assembled, of which 3,145 were differentially expressed between stages and/or color morphs. Depending on the developmental stage, between 547 and 1420 transcripts were significantly differentially expressed between brown and red wing morphs. These extensive differences in gene expression stand in stark contrast to the much smaller numbers found in previous studies on genetic wing pattern variation, and suggest that environmentally induced phenotypic shifts may arise from very broad systemic processes. Overall gene ontology (GO) analyses revealed that genes associated with structural constituents of ribosomes and oxygen transport were significantly upregulated in the pale brown morph, while genes associated with peptidase activity were very significantly upregulated in the dark red morph. Focused analyses of candidate endocrine and pigmentation pathways revealed a number of notable genes upregulated in the red morph, including several ecdysone-related genes and cinnabar, an ommochrome pigment gene implicated in color pattern variation in other butterflies. Surprisingly, we found numerous melanin-related transcripts, including tan and yellow-family genes, strongly upregulated in the red morph, leading us to speculate that red pigmentation in autumn J. coenia may include red or brown melanins in addition to ommochromes. While we identified several endocrine and pigmentation genes as obvious candidates for color morph differentiation, we speculate that the majority of gene expression differences we observed were due to thermal stress response. The buckeye transcriptome provides a basis for further developmental studies of phenotypic plasticity. mRNA profiling of hind wings from 4 developmental stages of two color morphs (Rosa and Linea) of the buckeye butterfly (J. coenia), generated by deep sequencing, in triplicate, using Illumina GAII or HiSeq 2000.

Project description:In the eastern United States the buckeye butterfly, Junonia coenia, shows a seasonal wing color polyphenism where adults emerging in the spring are pale brown, while those emerging in the autumn are dark red. This variation can be artificially induced in laboratory colonies, thus making J. coenia a useful model system to examine the developmental basis of phenotypic plasticity. We used RNA-seq to generate the first set of assembled transcripts for this species while simultaneously quantifying relative gene expression associated with development of alternative seasonal color morphs. The assembled consolidated wing transcriptome was 77.55 Mb. 16,251 contigs of over 1000bp in length were assembled, of which 3,145 were differentially expressed between stages and/or color morphs. Depending on the developmental stage, between 547 and 1420 transcripts were significantly differentially expressed between brown and red wing morphs. These extensive differences in gene expression stand in stark contrast to the much smaller numbers found in previous studies on genetic wing pattern variation, and suggest that environmentally induced phenotypic shifts may arise from very broad systemic processes. Overall gene ontology (GO) analyses revealed that genes associated with structural constituents of ribosomes and oxygen transport were significantly upregulated in the pale brown morph, while genes associated with peptidase activity were very significantly upregulated in the dark red morph. Focused analyses of candidate endocrine and pigmentation pathways revealed a number of notable genes upregulated in the red morph, including several ecdysone-related genes and cinnabar, an ommochrome pigment gene implicated in color pattern variation in other butterflies. Surprisingly, we found numerous melanin-related transcripts, including tan and yellow-family genes, strongly upregulated in the red morph, leading us to speculate that red pigmentation in autumn J. coenia may include red or brown melanins in addition to ommochromes. While we identified several endocrine and pigmentation genes as obvious candidates for color morph differentiation, we speculate that the majority of gene expression differences we observed were due to thermal stress response. The buckeye transcriptome provides a basis for further developmental studies of phenotypic plasticity.

Dataset Information

The effects of weak genetic perturbations on the transcriptome of the wing imaginal disc, and its association with wing shape in Drosophila melanogaster

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