Daniel Hahn | University of Florida (original) (raw)

Papers by Daniel Hahn

Research paper thumbnail of Differences in performance and transcriptome-wide gene expression associated with Rhagoletis (Diptera: Tephritidae) larvae feeding in alternate host fruit environments

Molecular ecology, Jan 7, 2015

Host race formation, the establishment of new populations using novel resources, is a major hypot... more Host race formation, the establishment of new populations using novel resources, is a major hypothesized mechanism of ecological speciation, especially in plant-feeding insects. The initial stages of host race formation will often involve phenotypic plasticity on the novel resource, with subsequent genetically based adaptations enhancing host-associated fitness differences. Several studies have explored the physiology of the plastic responses of insects to novel host environments. However, the mechanisms underlying evolved differences among host races and species remain poorly understood. Here we demonstrate a reciprocal performance difference for larval survival between two closely related species of Rhagoletis flies, R. pomonella and R. zephyria, specialized for feeding in apple and snowberry fruit, respectively. Microarray analysis of fly larvae feeding in apples versus snowberries revealed patterns of transcriptome-wide differential gene expression consistent with both plastic a...

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Research paper thumbnail of Constraints, independence, and evolution of thermal plasticity: Probing genetic architecture of long- and short-term thermal acclimation

Proceedings of the National Academy of Sciences of the United States of America, Jan 24, 2015

Seasonal and daily thermal variation can limit species distributions because of physiological tol... more Seasonal and daily thermal variation can limit species distributions because of physiological tolerances. Low temperatures are particularly challenging for ectotherms, which use both basal thermotolerance and acclimation, an adaptive plastic response, to mitigate thermal stress. Both basal thermotolerance and acclimation are thought to be important for local adaptation and persistence in the face of climate change. However, the evolutionary independence of basal and plastic tolerances remains unclear. Acclimation can occur over longer (seasonal) or shorter (hours to days) time scales, and the degree of mechanistic overlap is unresolved. Using a midlatitude population of Drosophila melanogaster, we show substantial heritable variation in both short- and long-term acclimation. Rapid cold hardening (short-term plasticity) and developmental acclimation (long-term plasticity) are positively correlated, suggesting shared mechanisms. However, there are independent components of these trait...

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Research paper thumbnail of Early Life Hormetic Treatments Decrease Irradiation-Induced Oxidative Damage, Increase Longevity, and Enhance Sexual Performance during Old Age in the Caribbean Fruit Fly

PLoS ONE, 2014

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Research paper thumbnail of 13 C NMR Metabolomics: Applications at Natural Abundance

Analytical Chemistry, 2014

(13)C NMR has many advantages for a metabolomics study, including a large spectral dispersion, na... more (13)C NMR has many advantages for a metabolomics study, including a large spectral dispersion, narrow singlets at natural abundance, and a direct measure of the backbone structures of metabolites. However, it has not had widespread use because of its relatively low sensitivity compounded by low natural abundance. Here we demonstrate the utility of high-quality (13)C NMR spectra obtained using a custom (13)C-optimized probe on metabolomic mixtures. A workflow was developed to use statistical correlations between replicate 1D (13)C and (1)H spectra, leading to composite spin systems that can be used to search publicly available databases for compound identification. This was developed using synthetic mixtures and then applied to two biological samples, Drosophila melanogaster extracts and mouse serum. Using the synthetic mixtures we were able to obtain useful (13)C-(13)C statistical correlations from metabolites with as little as 60 nmol of material. The lower limit of (13)C NMR detection under our experimental conditions is approximately 40 nmol, slightly lower than the requirement for statistical analysis. The (13)C and (1)H data together led to 15 matches in the database compared to just 7 using (1)H alone, and the (13)C correlated peak lists had far fewer false positives than the (1)H generated lists. In addition, the (13)C 1D data provided improved metabolite identification and separation of biologically distinct groups using multivariate statistical analysis in the D. melanogaster extracts and mouse serum.

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Research paper thumbnail of Vitellogenin RNAi Halts Ovarian Growth and Diverts Reproductive Proteins and Lipids in Young Grasshoppers

Integrative and Comparative Biology, 2014

Reduced reproduction extends lifespan of females in many animals. To test the effects of reproduc... more Reduced reproduction extends lifespan of females in many animals. To test the effects of reproduction on storage of macronutrients, we block reproductive output in the lubber grasshopper by injecting RNAi against the precursor to egg-yolk protein, vitellogenin, in early adulthood. Controls were injected with either buffer or RNAi against the major storage protein in the hemolymph, hexamerin-90. Vitellogenin RNAi greatly reduced both levels of mRNA for vitellogenin and ovarian growth, in comparison to both controls. Fat body mass was increased upon vitellogenin RNAi, but concentrations of the three hexameric storage proteins from the hemolymph were not. Surprisingly, hemolymph vitellogenin levels were increased upon vitellogenin RNAi. Total reproductive protein (hemolymph vitellogenin plus ovarian vitellin) was unchanged by vitellogenin RNAi, as reproductive protein was diverted to the hemolymph. Similarly, the increased lipid storage upon vitellogenin RNAi was largely attributable to the reduction in lipid in the ovary, due to decreased ovarian growth. A BLAST search revealed that the 515 bp sequence of vitellogenin used for RNAi had three 11 bp regions identical to the vitellogenin receptor of the cockroach Leucophaea maderae. This suggests that our treatment, in addition to reducing levels of vitellogenin transcript, may have also blocked transport of vitellogenin from the hemolymph to the ovary. This would be consistent with halted ovarian growth simultaneous with high levels of vitellogenin in the hemolymph. Nonetheless, the accumulation of vitellogenin, instead of hexameric storage proteins, is inconsistent with a simple model of the trade-off between reproduction and storage. This was observed in young females; future studies will address whether investment of proteins may shift to the soma as individuals age. Overall, our results suggest that blockage of reproduction in young grasshoppers redirects lipids to storage and reproductive proteins to the hemolymph.

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Research paper thumbnail of Meeting the energetic demands of insect diapause: Nutrient storage and utilization

Journal of Insect Physiology, 2007

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Research paper thumbnail of Life-history plasticity after attaining a dietary threshold for reproduction is associated with protein storage in flesh flies

Functional Ecology, 2008

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Research paper thumbnail of Gene discovery using massively parallel pyrosequencing to develop ESTs for the flesh fly Sarcophaga crassipalpis

BMC Genomics, 2009

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Research paper thumbnail of Cold adaptation shapes the robustness of metabolic networks in Drosophila melanogaster

Evolution, 2014

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Research paper thumbnail of Differences in performance and transcriptome-wide gene expression associated with Rhagoletis (Diptera: Tephritidae) larvae feeding in alternate host fruit environments

Molecular ecology, Jan 7, 2015

Host race formation, the establishment of new populations using novel resources, is a major hypot... more Host race formation, the establishment of new populations using novel resources, is a major hypothesized mechanism of ecological speciation, especially in plant-feeding insects. The initial stages of host race formation will often involve phenotypic plasticity on the novel resource, with subsequent genetically based adaptations enhancing host-associated fitness differences. Several studies have explored the physiology of the plastic responses of insects to novel host environments. However, the mechanisms underlying evolved differences among host races and species remain poorly understood. Here we demonstrate a reciprocal performance difference for larval survival between two closely related species of Rhagoletis flies, R. pomonella and R. zephyria, specialized for feeding in apple and snowberry fruit, respectively. Microarray analysis of fly larvae feeding in apples versus snowberries revealed patterns of transcriptome-wide differential gene expression consistent with both plastic a...

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Research paper thumbnail of Constraints, independence, and evolution of thermal plasticity: Probing genetic architecture of long- and short-term thermal acclimation

Proceedings of the National Academy of Sciences of the United States of America, Jan 24, 2015

Seasonal and daily thermal variation can limit species distributions because of physiological tol... more Seasonal and daily thermal variation can limit species distributions because of physiological tolerances. Low temperatures are particularly challenging for ectotherms, which use both basal thermotolerance and acclimation, an adaptive plastic response, to mitigate thermal stress. Both basal thermotolerance and acclimation are thought to be important for local adaptation and persistence in the face of climate change. However, the evolutionary independence of basal and plastic tolerances remains unclear. Acclimation can occur over longer (seasonal) or shorter (hours to days) time scales, and the degree of mechanistic overlap is unresolved. Using a midlatitude population of Drosophila melanogaster, we show substantial heritable variation in both short- and long-term acclimation. Rapid cold hardening (short-term plasticity) and developmental acclimation (long-term plasticity) are positively correlated, suggesting shared mechanisms. However, there are independent components of these trait...

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Research paper thumbnail of Early Life Hormetic Treatments Decrease Irradiation-Induced Oxidative Damage, Increase Longevity, and Enhance Sexual Performance during Old Age in the Caribbean Fruit Fly

PLoS ONE, 2014

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Research paper thumbnail of 13 C NMR Metabolomics: Applications at Natural Abundance

Analytical Chemistry, 2014

(13)C NMR has many advantages for a metabolomics study, including a large spectral dispersion, na... more (13)C NMR has many advantages for a metabolomics study, including a large spectral dispersion, narrow singlets at natural abundance, and a direct measure of the backbone structures of metabolites. However, it has not had widespread use because of its relatively low sensitivity compounded by low natural abundance. Here we demonstrate the utility of high-quality (13)C NMR spectra obtained using a custom (13)C-optimized probe on metabolomic mixtures. A workflow was developed to use statistical correlations between replicate 1D (13)C and (1)H spectra, leading to composite spin systems that can be used to search publicly available databases for compound identification. This was developed using synthetic mixtures and then applied to two biological samples, Drosophila melanogaster extracts and mouse serum. Using the synthetic mixtures we were able to obtain useful (13)C-(13)C statistical correlations from metabolites with as little as 60 nmol of material. The lower limit of (13)C NMR detection under our experimental conditions is approximately 40 nmol, slightly lower than the requirement for statistical analysis. The (13)C and (1)H data together led to 15 matches in the database compared to just 7 using (1)H alone, and the (13)C correlated peak lists had far fewer false positives than the (1)H generated lists. In addition, the (13)C 1D data provided improved metabolite identification and separation of biologically distinct groups using multivariate statistical analysis in the D. melanogaster extracts and mouse serum.

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Research paper thumbnail of Vitellogenin RNAi Halts Ovarian Growth and Diverts Reproductive Proteins and Lipids in Young Grasshoppers

Integrative and Comparative Biology, 2014

Reduced reproduction extends lifespan of females in many animals. To test the effects of reproduc... more Reduced reproduction extends lifespan of females in many animals. To test the effects of reproduction on storage of macronutrients, we block reproductive output in the lubber grasshopper by injecting RNAi against the precursor to egg-yolk protein, vitellogenin, in early adulthood. Controls were injected with either buffer or RNAi against the major storage protein in the hemolymph, hexamerin-90. Vitellogenin RNAi greatly reduced both levels of mRNA for vitellogenin and ovarian growth, in comparison to both controls. Fat body mass was increased upon vitellogenin RNAi, but concentrations of the three hexameric storage proteins from the hemolymph were not. Surprisingly, hemolymph vitellogenin levels were increased upon vitellogenin RNAi. Total reproductive protein (hemolymph vitellogenin plus ovarian vitellin) was unchanged by vitellogenin RNAi, as reproductive protein was diverted to the hemolymph. Similarly, the increased lipid storage upon vitellogenin RNAi was largely attributable to the reduction in lipid in the ovary, due to decreased ovarian growth. A BLAST search revealed that the 515 bp sequence of vitellogenin used for RNAi had three 11 bp regions identical to the vitellogenin receptor of the cockroach Leucophaea maderae. This suggests that our treatment, in addition to reducing levels of vitellogenin transcript, may have also blocked transport of vitellogenin from the hemolymph to the ovary. This would be consistent with halted ovarian growth simultaneous with high levels of vitellogenin in the hemolymph. Nonetheless, the accumulation of vitellogenin, instead of hexameric storage proteins, is inconsistent with a simple model of the trade-off between reproduction and storage. This was observed in young females; future studies will address whether investment of proteins may shift to the soma as individuals age. Overall, our results suggest that blockage of reproduction in young grasshoppers redirects lipids to storage and reproductive proteins to the hemolymph.

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Research paper thumbnail of Meeting the energetic demands of insect diapause: Nutrient storage and utilization

Journal of Insect Physiology, 2007

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Life-history plasticity after attaining a dietary threshold for reproduction is associated with protein storage in flesh flies

Functional Ecology, 2008

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Gene discovery using massively parallel pyrosequencing to develop ESTs for the flesh fly Sarcophaga crassipalpis

BMC Genomics, 2009

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Cold adaptation shapes the robustness of metabolic networks in Drosophila melanogaster

Evolution, 2014

Bookmarks Related papers MentionsView impact