Project description:The study of orchid mycorrhizal interactions is particularly complex because of the peculiar life cycle of these plants and their diverse trophic strategies. Here, large-scale transcriptomics has been applied to investigate gene expression in the mycorrhizal roots of the terrestrial mixotrophic orchid Limodorum abortivum under natural conditions. Our results provide new insights into the mechanisms underlying plant-fungus interactions in orchids and in particular on the plant responses to the mycorrhizal symbiont(s) in adult roots. Comparison with gene expression in mycorrhizal roots of another orchid species, Oeceoclades maculata, suggests that amino acids may represent the main nitrogen source in both protocorms and adult orchids, at least for mixotrophic species. The upregulation, in mycorrhizal L. abortivum roots, of some symbiotic molecular marker genes identified in mycorrhizal roots from other orchids as well as in arbuscular mycorrhiza, suggests a common plant core of genes in endomycorrhizal symbioses. Further efforts will be required to understand whether the specificities of orchid mycorrhiza depend on fine-tuned regulation of these common components, or whether specific additional genes are involved.
Project description:Free-breeding dogs have occupied the Galápagos islands at least since the 1830s, however, it was not until the 1900s that dog populations grew substantially, endangering wildlife and spreading disease. In 1981, authorities sanctioned the culling of free-roaming dogs. Yet there are currently large free-roaming dog populations of unknown ancestry on the islands of Isabela and Santa Cruz, whose ancestry has never been assessed on a genome-wide scale. Thus, we performed a complete genomic analysis of the current Galápagos dog population as well as historical Galápagos dogs sampled between 1969 and 2003, testing for population structure, admixture, and shared ancestry. Our dataset included samples from 187 modern and six historical Galápagos dogs, together with whole genome sequence from over 2,000 modern purebred and village dogs. Our results indicate that modern Galápagos dogs are recently admixed with purebred dogs but show no evidence of a population bottleneck related to the culling. Additionally, IBD analyses reveal evidence of shared shepherd-dog ancestry in the historical Galápagos dogs. Overall, our results demonstrate that the 1980s culling of dogs was ineffective in controlling population size and did little to reduce genetic diversity, instead producing a stable and expanding population with genomic signatures of historical dogs remaining today. The insights from this study can be used to improve population control strategies for the Galápagos Islands and other endangered endemic communities worldwide.
Project description:We used custom Nimblegen microarrays representing whole-larval transcriptomes for two species (Erynnis propertius [this submission] and Papilio zelicaon [submitted seperately]) to assess gene expression differences affecting tolerance to climatic regimes. Many individuals were sourced from populations from the northern periphery and center of the species' (shared) range; these were each divided into groups treated under peripheral and central climate regimes, resulting in 4 experimental groups for each species (Peripheral Source, Peripheral treatment; Peripheral Source, Central Treatment; Central Source, Peripheral Treatment; Central Source, Central Treatment). Using technical microarray replicates allowed us to use ANOVA to identify genes whose expression may underlie local adaptation to climate (i.e., those showing an interaction term between source and population). Abstract: Population differences may determine geographic range shifts and adaptive evolution under climate change. Local adaptation in peripheral populations could preclude or slow range expansions, and populations with different genetic make-up could have distinct trajectories that produce complex spatial patterns of population change. To investigate the genetic extent of local responses to climate change, we exposed poleward-periphery and central populations of two Lepidoptera to reciprocal, common-garden climatic conditions and compared whole-transcriptome expression. We found significant expression differences between populations in both species. In addition, several hundred genes including genes involved in energy metabolism and oxidative stress responded in a localized fashion in the species that exhibits greater population structure and local adaptation. Expression levels of these genes are most divergent in the same environment in which we previously detected phenotypic divergence in metabolism. By contrast, we found no localized genes in the species with higher gene flow, reflecting the lack of previously observed local adaptation. These results suggest that population differences do not generalize easily, even for related species living in the same climate, but some taxa deserve population-level consideration when predicting the effects of climate change.
Project description:We used custom Nimblegen microarrays representing whole-larval transcriptomes for two species (Papilio zelicaon [this submission] and Erynnis propertius [submitted seperately]) to assess gene expression differences affecting tolerance to climatic regimes. Many individuals were sourced from populations from the northern periphery and center of the species' (shared) range; these were each divided into groups treated under peripheral and central climate regimes, resulting in 4 experimental groups for each species (Peripheral Source, Peripheral treatment; Peripheral Source, Central Treatment; Central Source, Peripheral Treatment; Central Source, Central Treatment). Using technical microarray replicates allowed us to use ANOVA to identify genes whose expression may underlie local adaptation to climate (i.e., those showing an interaction term between source and population). Abstract: Population differences may determine geographic range shifts and adaptive evolution under climate change. Local adaptation in peripheral populations could preclude or slow range expansions, and populations with different genetic make-up could have distinct trajectories that produce complex spatial patterns of population change. To investigate the genetic extent of local responses to climate change, we exposed poleward-periphery and central populations of two Lepidoptera to reciprocal, common-garden climatic conditions and compared whole-transcriptome expression. We found significant expression differences between populations in both species. In addition, several hundred genes including genes involved in energy metabolism and oxidative stress responded in a localized fashion in the species that exhibits greater population structure and local adaptation. Expression levels of these genes are most divergent in the same environment in which we previously detected phenotypic divergence in metabolism. By contrast, we found no localized genes in the species with higher gene flow, reflecting the lack of previously observed local adaptation. These results suggest that population differences do not generalize easily, even for related species living in the same climate, but some taxa deserve population-level consideration when predicting the effects of climate change.
Project description:We used custom Nimblegen microarrays representing whole-larval transcriptomes for two species (Erynnis propertius [this submission] and Papilio zelicaon [submitted seperately]) to assess gene expression differences affecting tolerance to climatic regimes. Many individuals were sourced from populations from the northern periphery and center of the species' (shared) range; these were each divided into groups treated under peripheral and central climate regimes, resulting in 4 experimental groups for each species (Peripheral Source, Peripheral treatment; Peripheral Source, Central Treatment; Central Source, Peripheral Treatment; Central Source, Central Treatment). Using technical microarray replicates allowed us to use ANOVA to identify genes whose expression may underlie local adaptation to climate (i.e., those showing an interaction term between source and population). Abstract: Population differences may determine geographic range shifts and adaptive evolution under climate change. Local adaptation in peripheral populations could preclude or slow range expansions, and populations with different genetic make-up could have distinct trajectories that produce complex spatial patterns of population change. To investigate the genetic extent of local responses to climate change, we exposed poleward-periphery and central populations of two Lepidoptera to reciprocal, common-garden climatic conditions and compared whole-transcriptome expression. We found significant expression differences between populations in both species. In addition, several hundred genes including genes involved in energy metabolism and oxidative stress responded in a localized fashion in the species that exhibits greater population structure and local adaptation. Expression levels of these genes are most divergent in the same environment in which we previously detected phenotypic divergence in metabolism. By contrast, we found no localized genes in the species with higher gene flow, reflecting the lack of previously observed local adaptation. These results suggest that population differences do not generalize easily, even for related species living in the same climate, but some taxa deserve population-level consideration when predicting the effects of climate change. Previously we sequenced and assembled whole larval transcriptome ESTs sourced from pooled central-population individuals subjected to environmental stressors (see O'Neil et al., 2008). From these assemblies custom Nimblegen microarrays were designed (Nimblegen, Inc.), representing 34,609 putative gene sequences for E. propertius (this submission) and 25,735 putative gene sequences for P. zelicaon (submitted seperately). Probe designs sought 5 representative 60mer probes for E.propertius and 4 representative probes for P. zelicaon. Messenger RNA was was sampled from multiple individuals of each experimental group and pooled before being converted to cDNA and hybridized to technical replicate microarrays. Three technical replicates for each experimental group were used, for a total of 12 microarrays (per species). Microarray data were log2 transformed and quintile-normalized (Bolstad et al. 2003) on a per-species basis.
Project description:We used custom Nimblegen microarrays representing whole-larval transcriptomes for two species (Papilio zelicaon [this submission] and Erynnis propertius [submitted seperately]) to assess gene expression differences affecting tolerance to climatic regimes. Many individuals were sourced from populations from the northern periphery and center of the species' (shared) range; these were each divided into groups treated under peripheral and central climate regimes, resulting in 4 experimental groups for each species (Peripheral Source, Peripheral treatment; Peripheral Source, Central Treatment; Central Source, Peripheral Treatment; Central Source, Central Treatment). Using technical microarray replicates allowed us to use ANOVA to identify genes whose expression may underlie local adaptation to climate (i.e., those showing an interaction term between source and population). Abstract: Population differences may determine geographic range shifts and adaptive evolution under climate change. Local adaptation in peripheral populations could preclude or slow range expansions, and populations with different genetic make-up could have distinct trajectories that produce complex spatial patterns of population change. To investigate the genetic extent of local responses to climate change, we exposed poleward-periphery and central populations of two Lepidoptera to reciprocal, common-garden climatic conditions and compared whole-transcriptome expression. We found significant expression differences between populations in both species. In addition, several hundred genes including genes involved in energy metabolism and oxidative stress responded in a localized fashion in the species that exhibits greater population structure and local adaptation. Expression levels of these genes are most divergent in the same environment in which we previously detected phenotypic divergence in metabolism. By contrast, we found no localized genes in the species with higher gene flow, reflecting the lack of previously observed local adaptation. These results suggest that population differences do not generalize easily, even for related species living in the same climate, but some taxa deserve population-level consideration when predicting the effects of climate change. Previously we sequenced and assembled whole larval transcriptome ESTs sourced from pooled central-population individuals subjected to environmental stressors (see O'Neil et al., 2008). From these assemblies custom Nimblegen microarrays were designed (Nimblegen, Inc.), representing 34,609 putative gene sequences for E. propertius (submitted separately) and 25,735 putative gene sequences for P. zelicaon (this submission). Probe designs sought 5 representative 60mer probes for E.propertius and 4 representative probes for P. zelicaon. Messenger RNA was was sampled from multiple individuals of each experimental group and pooled before being converted to cDNA and hybridized to technical replicate microarrays. Three technical replicates for each experimental group were used, for a total of 12 microarrays (per species). Microarray data were log2 transformed and quintile-normalized (Bolstad et al. 2003) on a per-species basis.
Project description:The Kashmiri population is an ethno-linguistic group that resides in the Kashmir Valley in northern India. A longstanding hypothesis is that this population derives ancestry from Jewish and/or Greek sources. There is historical and archaeological evidence of ancient Greek presence in India and Kashmir. Further, some historical accounts suggest ancient Hebrew ancestry as well. To date, it has not been determined whether signatures of Greek or Jewish admixture can be detected in the Kashmiri population. Using genome-wide genotyping and admixture detection methods, we determined there are no significant or substantial signs of Greek or Jewish admixture in modern-day Kashmiris. The ancestry of Kashmiri Tibetans was also determined, which showed signs of admixture with populations from northern India and west Eurasia. These results contribute to our understanding of the existing population structure in northern India and its surrounding geographical areas.
Project description:Orchids form an endomycorrhizal association with fungal symbionts mainly belonging to Basidiomycetes. The molecular events taking place in orchid mycorrhiza are poorly understood, although the cellular changes necessary to accommodate the fungus and to control nutrient exchange between the symbionts imply a modulation of gene expression. In this study, we used proteomic and transcriptomic approaches to identify changes in the steady-state levels of proteins and transcripts in roots of the green terrestrial orchid Oeceoclades maculata. When mycorrhizal and non-mycorrhizal roots from the same individuals of O. maculata were compared, 94 proteins showed differential accumulation using the label-free protein quantitation approach, 86 using isobaric tagging (iTRAQ) and 60 using 2D-differential electrophoresis. After de novo assembly of transcriptomic data, 11,179 plant transcripts were found to be differentially expressed and 2175 were successfully annotated. The annotated plant transcripts allowed the identification of up- and down-regulated metabolic pathways in mycorrhizal roots, as compared to non-mycorrhizal roots. Overall, proteomics and transcriptomics revealed in mycorrhizal roots increased levels of transcription factors and nutrient transporters, as well as ethylene-related proteins. The expression pattern of proteins and transcripts involved in plant defense responses suggest that plant defense is reduced in mycorrhizal roots. These results expand our current knowledge towards a better understanding of the orchid mycorrhizal symbiosis in adult plants under natural conditions.