The Experts below are selected from a list of 99 Experts worldwide ranked by ideXlab platform
Alexander V. Badyaev - One of the best experts on this subject based on the ideXlab platform.
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Evolution of "determinants" in sex-determination: a novel hypothesis for the origin of Environmental contingencies in avian sex-bias.
Seminars in cell & developmental biology, 2008Co-Authors: Tobias Uller, Alexander V. BadyaevAbstract:Abstract Sex-determination is commonly categorized as either “genetic” or “Environmental”—a classification that obscures the origin of this dichotomy and the evolution of sex-determining factors. The current focus on static outcomes of sex-determination provides little insight into the dynamic developmental processes by which some mechanisms acquire the role of sex determinants. Systems that combine “genetic” pathways of sex-determination (i.e., sex chromosomes) with “Environmental” pathways (e.g., epigenetically induced segregation distortion) provide an opportunity to examine the evolutionary relationships between the two classes of processes and, ultimately, illuminate the evolution of sex-determining systems. Taxa with sex chromosomes typically undergo an evolutionary reduction in size of one of the sex chromosomes due to suppressed recombination, resulting in pronounced dimorphism of the sex chromosomes, and setting the stage for emergence of epigenetic compensatory mechanisms regulating meiotic segregation of heteromorphic sex chromosomes. Here we propose that these dispersed and redundant regulatory mechanisms enable Environmental Contingency in genetic sex-determination in birds and account for frequently documented context-dependence in avian sex-determination. We examine the evolution of directionality in such sex-determination as a result of exposure of epigenetic regulators of meiosis to natural selection and identify a central role of hormones in integrating female reproductive homeostasis, resource allocation to oocytes, and offspring sex. This approach clarifies the evolutionary relationship between sex-specific molecular genetic mechanisms of sex-determination and non-sex-specific epigenetic regulators of meiosis and demonstrates that both can determine sex. Our perspective shows how non-sex-specific mechanisms can acquire sex-determining function and, by establishing the explicit link between physiological integration of oogenesis and sex-determination, opens new avenues to the studies of adaptive sex-bias and sex-specific resource allocation in species with genetic sex-determination.
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Evolvability and Robustness in Color Displays: Bridging the Gap between Theory and Data
Evolutionary Biology, 2007Co-Authors: Alexander V. BadyaevAbstract:Evolution of diet-derived sexual ornaments—some of the most spectacular and diverse traits in the living world—highlights the gap between modern evolutionary theory and empirical data on the origin and inheritance of complex environment-dependent traits. Specifically, current theory offers little insight into how strong Environmental Contingency of diet-dependent color biosynthesis and Environmental variability in precursor supply can be reconciled with extensive evolutionary elaboration, diversification, and convergence of diet-dependent displays among animal taxa. Moreover, biosynthetic pathways of diet-derived displays combine seemingly irreconcilable robustness, lability, and modularity to facilitate elaboration under variable Environmental conditions. Here I show that an ontogenetic decrease in the predictability of an association between organismal and Environmental components of color biosynthesis and the corresponding evolutionary transition from short-term epigenetic inheritance of peripheral biosynthetic components to genetic inheritance of the most reliable upstream components link the causes of developmental variation with the causes of inheritance in diet-derived displays. Using carotenoid-based colors as an empirical model, I outline general principles of a testable evolutionary framework of diversification and functional robustness of diet-derived displays, and suggest that such a framework provides insight into the foundational question of evolutionary biology—how to connect causes of within-generation developmental variation with causes of among-generation and among-taxa variation and thus with causes of evolution?
Leah E. Cowen - One of the best experts on this subject based on the ideXlab platform.
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Mapping the Hsp90 genetic interaction network in Candida albicans reveals Environmental Contingency and rewired circuitry.
PLoS genetics, 2012Co-Authors: Stephanie Diezmann, Magali Michaut, Rebecca S. Shapiro, Gary D. Bader, Leah E. CowenAbstract:The molecular chaperone Hsp90 regulates the folding of diverse signal transducers in all eukaryotes, profoundly affecting cellular circuitry. In fungi, Hsp90 influences development, drug resistance, and evolution. Hsp90 interacts with ∼10% of the proteome in the model yeast Saccharomyces cerevisiae, while only two interactions have been identified in Candida albicans, the leading fungal pathogen of humans. Utilizing a chemical genomic approach, we mapped the C. albicans Hsp90 interaction network under diverse stress conditions. The chaperone network is Environmentally contingent, and most of the 226 genetic interactors are important for growth only under specific conditions, suggesting that they operate downstream of Hsp90, as with the MAPK Hog1. Few interactors are important for growth in many environments, and these are poised to operate upstream of Hsp90, as with the protein kinase CK2 and the transcription factor Ahr1. We establish Environmental Contingency in the first chaperone network of a fungal pathogen, novel effectors upstream and downstream of Hsp90, and network rewiring over evolutionary time.
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hsp90 potentiates the rapid evolution of new traits drug resistance in diverse fungi
Science, 2005Co-Authors: Leah E. Cowen, Susan LindquistAbstract:Hsp90 is a molecular chaperone for many signal transducers and may influence evolution by releasing previously silent genetic variation in response to Environmental change. In fungi separated by ∼800 million years of evolution, Hsp90 potentiated the evolution of drug resistance in a different way, by enabling new mutations to have immediate phenotypic consequences. Resistance was abrogated by Hsp90 inhibitors and by febrile temperatures, suggesting new therapeutic strategies and a clinical benefit of fever. During selection in a human host, drug resistance that was initially Hsp90-dependent evolved toward independence. Thus, Hsp90 can act in diverse ways to couple Environmental Contingency to the emergence and fixation of new traits.
Ranjay Gulati - One of the best experts on this subject based on the ideXlab platform.
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Environmental Demands and the Emergence of Social Structure Technological Dynamism and Interorganizational Network Forms
Administrative Science Quarterly, 2015Co-Authors: Adam Tatarynowicz, Maxim Sytch, Ranjay GulatiAbstract:This study investigates the origins of variation in the structures of interorganizational networks across industries. We combine empirical analyses of existing interorganizational networks with an agent-based simulation model of network emergence. Our insights are twofold. First, we find that differences in technological dynamism across industries and the concomitant demands for value creation engender variations in firms’ collaborative behaviors. On average, firms in technologically dynamic industries pursue more open ego networks, which fosters access to new and diverse resources that help sustain continuous innovation. In contrast, firms in technologically stable industries on average pursue more closed ego networks, which fosters reliable collaboration and helps preserve existing resources. Second, we show that because of the observed cross-industry differences in firms’ collaborative behaviors, the emergent industry-wide networks take on distinct structural forms. Technologically stable industries feature clan networks, characterized by low network connectedness and rather strong community structures. Technologically dynamic industries, in turn, feature community networks, characterized by high network connectedness and medium-to-strong community structures. Convention networks, which feature high network connectedness and weak community structures, were not evident among the empirical networks we examined. Taken together, our findings advance an Environmental Contingency theory of network formation.
Tobias Uller - One of the best experts on this subject based on the ideXlab platform.
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Evolution of "determinants" in sex-determination: a novel hypothesis for the origin of Environmental contingencies in avian sex-bias.
Seminars in cell & developmental biology, 2008Co-Authors: Tobias Uller, Alexander V. BadyaevAbstract:Abstract Sex-determination is commonly categorized as either “genetic” or “Environmental”—a classification that obscures the origin of this dichotomy and the evolution of sex-determining factors. The current focus on static outcomes of sex-determination provides little insight into the dynamic developmental processes by which some mechanisms acquire the role of sex determinants. Systems that combine “genetic” pathways of sex-determination (i.e., sex chromosomes) with “Environmental” pathways (e.g., epigenetically induced segregation distortion) provide an opportunity to examine the evolutionary relationships between the two classes of processes and, ultimately, illuminate the evolution of sex-determining systems. Taxa with sex chromosomes typically undergo an evolutionary reduction in size of one of the sex chromosomes due to suppressed recombination, resulting in pronounced dimorphism of the sex chromosomes, and setting the stage for emergence of epigenetic compensatory mechanisms regulating meiotic segregation of heteromorphic sex chromosomes. Here we propose that these dispersed and redundant regulatory mechanisms enable Environmental Contingency in genetic sex-determination in birds and account for frequently documented context-dependence in avian sex-determination. We examine the evolution of directionality in such sex-determination as a result of exposure of epigenetic regulators of meiosis to natural selection and identify a central role of hormones in integrating female reproductive homeostasis, resource allocation to oocytes, and offspring sex. This approach clarifies the evolutionary relationship between sex-specific molecular genetic mechanisms of sex-determination and non-sex-specific epigenetic regulators of meiosis and demonstrates that both can determine sex. Our perspective shows how non-sex-specific mechanisms can acquire sex-determining function and, by establishing the explicit link between physiological integration of oogenesis and sex-determination, opens new avenues to the studies of adaptive sex-bias and sex-specific resource allocation in species with genetic sex-determination.
Adam Tatarynowicz - One of the best experts on this subject based on the ideXlab platform.
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Environmental Demands and the Emergence of Social Structure Technological Dynamism and Interorganizational Network Forms
Administrative Science Quarterly, 2015Co-Authors: Adam Tatarynowicz, Maxim Sytch, Ranjay GulatiAbstract:This study investigates the origins of variation in the structures of interorganizational networks across industries. We combine empirical analyses of existing interorganizational networks with an agent-based simulation model of network emergence. Our insights are twofold. First, we find that differences in technological dynamism across industries and the concomitant demands for value creation engender variations in firms’ collaborative behaviors. On average, firms in technologically dynamic industries pursue more open ego networks, which fosters access to new and diverse resources that help sustain continuous innovation. In contrast, firms in technologically stable industries on average pursue more closed ego networks, which fosters reliable collaboration and helps preserve existing resources. Second, we show that because of the observed cross-industry differences in firms’ collaborative behaviors, the emergent industry-wide networks take on distinct structural forms. Technologically stable industries feature clan networks, characterized by low network connectedness and rather strong community structures. Technologically dynamic industries, in turn, feature community networks, characterized by high network connectedness and medium-to-strong community structures. Convention networks, which feature high network connectedness and weak community structures, were not evident among the empirical networks we examined. Taken together, our findings advance an Environmental Contingency theory of network formation.