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Jennifer A Brisson - One of the best experts on this subject based on the ideXlab platform.
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ecdysone signaling underlies the pea aphid transgenerational wing Polyphenism
Proceedings of the National Academy of Sciences of the United States of America, 2017Co-Authors: Neetha Nanoth Vellichirammal, Purba Gupta, Tannice A Hall, Jennifer A BrissonAbstract:The wing Polyphenism of pea aphids is a compelling laboratory model with which to study the molecular mechanisms underlying phenotypic plasticity. In this Polyphenism, environmental stressors such as high aphid density cause asexual, viviparous adult female aphids to alter the developmental fate of their embryos from wingless to winged morphs. This Polyphenism is transgenerational, in that the pea aphid mother experiences the environmental signals, but it is her offspring that are affected. Previous research suggested that the steroid hormone ecdysone may play a role in this Polyphenism. Here, we analyzed ecdysone-related gene expression patterns and found that they were consistent with a down-regulation of the ecdysone pathway being involved in the production of winged offspring. We therefore predicted that reduced ecdysone signaling would result in more winged offspring. Experimental injections of ecdysone or its analog resulted in a decreased production of winged offspring. Conversely, interfering with ecdysone signaling using an ecdysone receptor antagonist or knocking down the ecdysone receptor gene with RNAi resulted in an increased production of winged offspring. Our results are therefore consistent with the idea that ecdysone plays a causative role in the regulation of the proportion of winged offspring produced in response to crowding in this Polyphenism. Our results also show that an environmentally regulated maternal hormone can mediate phenotype production in the next generation, as well as provide significant insight into the molecular mechanisms underlying the functioning of transgenerational phenotypic plasticity.
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a case for a joint strategy of diversified bet hedging and plasticity in the pea aphid wing Polyphenism
Biology Letters, 2016Co-Authors: Mary E Grantham, Chris J Antonio, Brian R Oneil, Yi Xiang Zhan, Jennifer A BrissonAbstract:Phenotypic plasticity and diversified bet hedging are strategies for coping with variable environments. Plasticity is favoured when an organism can predict future conditions using environmental cues, while bet hedging is favoured when predictive cues are not available. Theoretical analyses suggest that many organisms should use a mixture of both strategies, because environments often present both scenarios. Here, we examine if the pea aphid wing Polyphenism, a well-known case of plasticity, is potentially a mixture of plasticity and bet hedging. In this Polyphenism, asexual females produce more winged offspring in crowded conditions, and wingless offspring in uncrowded conditions. We find that pea aphids use plasticity to respond to crowding and we find considerable genetic variation for this response. We further show that individual aphids produce both winged and wingless offspring, consistent with the variability expected in a bet hedging trait. We conclude that the pea aphid wing Polyphenism system is probably a mixture of plasticity and bet hedging. Our study adds to a limited list of empirical studies examining mixed strategy usage, and suggests that mixed strategies may be common in dispersal traits.
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the genomewide transcriptional response underlying the pea aphid wing Polyphenism
Molecular Ecology, 2016Co-Authors: Neetha Nanoth Vellichirammal, Nandakumar Madayiputhiya, Jennifer A BrissonAbstract:Phenotypic plasticity is a key life history strategy used by many plants and animals living in heterogeneous environments. A multitude of studies have investigated the costs and limits of plasticity, as well as the conditions under which it evolves. Much less well understood are the molecular genetic mechanisms that enable an organism to sense its environment and respond in a plastic manner. The pea aphid wing Polyphenism is a compelling laboratory model to study these mechanisms. In this Polyphenism, environmental stressors like high density cause asexual, viviparous adult female aphids to change the development of their embryos from wingless to winged morphs. The life history trade-offs between the two morphs have been intensively studied, but the molecular mechanisms underlying this process remain largely unknown. We therefore performed a genomewide study of the maternal transcriptome at two time points with and without a crowding stress to discover the maternal molecular changes that lead to the development of winged vs. wingless offspring. We observed significant transcriptional changes in genes associated with odorant binding, neurotransmitter transport, hormonal activity and chromatin remodelling in the maternal transcriptome. We also found that titres of serotonin, dopamine and octopamine were higher in solitary compared to crowded aphids. We use these results to posit a model for how maternal signals inform a developing embryo to be winged or wingless. Our findings add significant insights into the identity of the molecular mechanisms that underlie environmentally induced morph determination and suggest a possible role for biogenic amine regulation in Polyphenisms generally.
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The right tools for the job: regulating polyphenic morph development in insects
Current opinion in insect science, 2016Co-Authors: Jennifer A Brisson, Gregory K DavisAbstract:Polyphenism is a form of developmental plasticity in which organisms respond to environmental cues by producing adaptive, discrete, alternative phenotypes known as morphs. The phenomenon is common and important as both a form of adaptation and a source of variation for natural selection. Understanding the evolution of Polyphenism will require understanding the proximate factors that regulate alternative morph production. Renewed interest and technological advances have fueled multiple approaches to the latter, including hormone manipulation studies, targeted transcriptomic studies, and epigenetic profiling. We review these studies and suggest that integration of multilayered approaches will be necessary to understand the complex mechanisms involved in regulating alternative morphologies.
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Integrative Genomic Approaches to Studying Epigenetic Mechanisms of Phenotypic Plasticity in the Aphid
2015Co-Authors: Mary Grantham, Jennifer A Brisson, Denis Tagu, Gaël Le TrionnaireAbstract:Phenotypic plasticity is the nongenic variation in phenotype due to environmental factors. It is a common phenomenon in the animal kingdom that is not well understood at the molecular level. A tenable form of phenotypic plasticity for molecular research is Polyphenism, which is an extreme form of phenotypic plasticity that results in discrete, alternative morphs. Epigenetic mechanisms have been hypothesized as the molecular regulators of Polyphenism, in particular DNA methylation and chromatin remodeling. The pea aphid exhibits multiple Polyphenisms including winged and wingless females during summer (wing Polyphenism) and asexual and sexual morphs during summer and fall, respectively (reproductive Polyphenism). The aphid is ideally situated for research into the molecular basis of Polyphenism, with a sequenced genome and multiple transcriptomic studies that have begun identifying key molecular regulators of these two Polyphenisms. The aphid also possesses the genes necessary for DNA methylation and chromatin remodeling. The pea aphid system is thus primed for future research into the epigenetic regulation of Polyphenisms
Toru Miura - One of the best experts on this subject based on the ideXlab platform.
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Aphid Polyphenisms: trans-generational developmental regulation through viviparity.
Frontiers in physiology, 2014Co-Authors: Kota Ogawa, Toru MiuraAbstract:Polyphenism, in which multiple discrete phenotypes develop from a single genotype, is considered to have contributed to the evolutionary success of aphids. Of the various Polyphenisms observed in the complex life cycle of aphids, the reproductive and wing Polyphenisms seen in most aphid species are conspicuous. In reproductive Polyphenism, the reproductive modes can change between viviparous parthenogenesis and sexual reproduction in response to the photoperiod. Under short-day conditions in autumn, sexual morphs (males and oviparous females) are produced parthenogenetically. Winged Polyphenism is observed in viviparous generations during summer, when winged or wingless (flightless) aphids are produced depending on a variety of environmental conditions (e.g. density, predators). Here, we review the physiological mechanisms underlying reproductive and wing Polyphenism in aphids. In reproductive Polyphenism, morph determination (male, oviparous or viviparous female) within mother aphids is regulated by juvenile hormone (JH) titers in the mothers. In wing Polyphenism, although JH is considered to play an important role in phenotype determination (winged or wingless), the role is still controversial. In both cases, the acquisition of viviparity in Aphididae is considered to be the basis for maternal regulation of these Polyphenisms, and through which environmental cues can be transferred to developing embryos through the physiological state of the mother. Although the mechanisms by which mothers alter the developmental programs of their progeny have not yet been clarified, continued developments in molecular biology will likely unravel these questions.
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Effect of juvenoids on predator-induced Polyphenism in the water flea, Daphnia pulex.
Journal of experimental zoology. Part A Ecological genetics and physiology, 2013Co-Authors: Hitoshi Miyakawa, Hiroki Gotoh, Naoki Sugimoto, Toru MiuraAbstract:In Daphnia pulex, juveniles form "neckteeth" a defensive structure on their heads, in response to predatory kairomones released by Chaoborus larvae. This phenomenon provides a model experimental system for the study of developmental mechanisms and evolutionary processes in predator-induced Polyphenisms. Although it is thought that kairomone signals are sensed and converted into physiological signals resulting in morphological changes, little is known about the endocrine and physiological mechanisms of this process. Juvenile hormones and related chemicals, that is, juvenoids, are key hormones responsible for various physiological events in insects, includingPolyphenisms. Insome crustaceans, methyl farnesoate(MF) is known toact asa juvenoid. In order to investigate the functions of juvenoids in defense morph formation, we treated daphnids with MF as well as JHIII (Juvenile Hormone III, an insect juvenoid) and fenoxycarb (a synthetic juvenile hormone analog) during their developmental stages. Strikingly, in the first-instar juveniles, all examined juvenoids stimulated the formation of neckteeth only in the presence of kairomones, not by themselves. This juvenoid effect on the neckteeth formation might be due to disturbance of the JH pathway. Juvenoid treatments reduced tail-spine length, whereas predatory kairomones are known to elongate tail spine. These results suggest that other physiological factors are responsible for the tail-spine elongation. J. Exp. Zool. 319A: 440-450, 2013. © 2013 Wiley Periodicals, Inc. Howtocitethisarticle:MiyakawaH,GotohH,SugimotoN,MiuraT.2013.Effectofjuvenoidson predator-induced Polyphenism in the water flea, Daphnia pulex. J. Exp. Zool. 319A:440-450.
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Differential regulations of wing and ovarian development and heterochronic changes of embryogenesis between morphs in wing Polyphenism of the vetch aphid
Evolution & Development, 2009Co-Authors: Asano Ishikawa, Toru MiuraAbstract:SUMMARY In wing Polyphenisms that produced alternative wing morphs depending on environmental conditions, the developmental regulations to balance between flight and reproductive abilities should be important. Many species of aphids exhibit wing Polyphenisms, and the development of wing and flight muscles is thought to incur costs of reproductive ability. To evaluate the relationship between flight and reproduction, the fecundity and the wing- and ovarian development in the parthenogenetic generations were compared between winged and wingless aphids in the vetch aphid Megoura crassicauda. Although no differences in offspring number and size were detected, the onset of larviposition after imaginal molt was delayed in winged adults. The comparison of growth in flight apparatus revealed that, after the second-instar nymphs, the flight-apparatus primordia of presumptive wingless aphids were degenerated while those of winged nymphs rapidly developed. In the ovaries of winged line, the embryo size was smaller and the embryonic stages were delayed from third to fifth instars, although these differences had disappeared by the time of larviposition. It is therefore likely that the delay in larviposition in winged aphids is due to the slower embryonic development. The correlation between embryo size and developmental stage suggests that the embryos of winged aphids are better developed than similarly sized embryos in wingless aphids. These heterochronic shifts would facilitate the rapid onset of larviposition after the dispersal flight. This developmental regulation of embryogenesis in the aphid wing Polyphenism is suggested to be an adaptation that compensates the delay of reproduction caused by the wing development.
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Caste-specific cytochrome P450 in the damp-wood termite Hodotermopsis sjostedti (Isoptera, Termopsidae).
Insect Molecular Biology, 2006Co-Authors: Richard Cornette, Tadao Matsumoto, Shigeyuki Koshikawa, Masaru Hojo, Toru MiuraAbstract:Termites are eusocial insects with a well-defined caste system, which is an example of Polyphenism. This Polyphenism is based on hormonally controlled differential gene expression. In the damp-wood termite Hodotermopsis sjostedti , we induced differentiation into the soldier caste by using juvenile hormone analogue treatment. We then investigated specific gene expression, which appeared during the hormonal response and triggered caste differentiation, using fluorescent differential display. A candidate cDNA sequence with similarity to cytochromes P450, CYP6AM1, was characterized and its transcript shown to be repressed between 1 and 3 days after hormone treatment. CYP6AM1 was specifically expressed in the fat body of pseudergates and soldiers. The putative function of this P450 is discussed with respect to the caste differentiation system.
Gregory A. Sword - One of the best experts on this subject based on the ideXlab platform.
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Polyphenism in insects.
Current biology : CB, 2011Co-Authors: Stephen J. Simpson, Gregory A. SwordAbstract:Polyphenism is the phenomenon where two or more distinct phenotypes are produced by the same genotype. Examples of Polyphenism provide some of the most compelling systems for the study of epigenetics. Polyphenisms are a major reason for the success of the insects, allowing them to partition life history stages (with larvae dedicated to feeding and growth, and adults dedicated to reproduction and dispersal), to adopt different phenotypes that best suit predictable environmental changes (seasonal morphs), to cope with temporally heterogeneous environments (dispersal morphs), and to partition labour within social groups (the castes of eusocial insects). We survey the status of research on some of the best known examples of insect Polyphenism, in each case considering the environmental cues that trigger shifts in phenotype, the neurochemical and hormonal pathways that mediate the transformation, the molecular genetic and epigenetic mechanisms involved in initiating and maintaining the Polyphenism, and the adaptive and life-history significance of the phenomenon. We conclude by highlighting some of the common features of these examples and consider future avenues for research on Polyphenism.
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Phase Polyphenism and preventative locust management.
Journal of insect physiology, 2010Co-Authors: Gregory A. Sword, Michel Lecoq, Stephen J. SimpsonAbstract:The ecology of phase Polyphenism plays a major role in locust swarm formation. We describe how recent advances in the understanding of phase Polyphenism can be combined with existing management approaches as part of a preventative Desert locust management strategy. We start with a brief overview of phase Polyphenism with particular emphasis on the role that resource distribution patterns play in the process of locust phase change. We then review current perspective on preventative locust management, and conclude by proposing a framework for quantitatively assessing the risk that phase change will occur in local locust populations. Importantly, the data required to implement this framework can be readily collected with little additional effort or cost just by slightly modifying locust habitat survey protocols that are already in operation. Incorporating gregarization risk assessment into existing preventative management strategies stands to make a considerable contribution toward realizing sustainable goals of reductions in the pesticide, manpower and financial support necessary to combat Desert locust upsurges, outbreaks and ultimately plagues.
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Behavioural phase Polyphenism in the Australian plague locust (Chortoicetes terminifera).
Biology Letters, 2009Co-Authors: Lindsey J. Gray, Gregory A. Sword, Michael L. Anstey, Fiona J. Clissold, Stephen J. SimpsonAbstract:Swarming and the expression of phase Polyphenism are defining characteristics of locust species. Increases in local population density mediate morphological, physiological and behavioural changes within individuals, which correlate with mass marching of juveniles in migratory bands and flying swarms of adults. The Australian plague locust (Chortoicetes terminifera) regularly forms migratory bands and swarms, but is claimed not to express phase Polyphenism and has accordingly been used to argue against a central role for phase change in locust swarming. We demonstrate that juvenile C. terminifera express extreme density-dependent behavioural phase Polyphenism. Isolated-reared juveniles are sedentary and repelled by conspecifics, whereas crowd-reared individuals are highly active and are attracted to conspecifics. In contrast to other major locust species, however, behavioural phase change does not accumulate across generations, but shifts completely within an individual's lifetime in response to a change in population density.
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Behavioural phase Polyphenism in the Australian plague locust (Chortoicetes terminifera).
Biology letters, 2009Co-Authors: Lindsey J. Gray, Gregory A. Sword, Michael L. Anstey, Fiona J. Clissold, Stephen J. SimpsonAbstract:Swarming and the expression of phase Polyphenism are defining characteristics of locust species. Increases in local population density mediate morphological, physiological and behavioural changes w...
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To be or not to be a locust? A comparative analysis of behavioral phase change in nymphs of Schistocerca americana and S. gregaria
Journal of insect physiology, 2003Co-Authors: Gregory A. SwordAbstract:Phenotypic plasticity in behavior induced by high rearing density is often part of a migratory syndrome in insects called phase Polyphenism. Among locust species, swarming and the expression of phase Polyphenism are highly correlated. The american grasshopper, Schistocerca americana, rarely swarms even though it is closely related to the swarming Old World desert locust, S. gregaria ,a s well as two swarming New World locusts. Anecdotal field observations of locust-like behavior in S. americana indicate that it may express behavioral phase Polyphenism, but empirical investigations are lacking. In this study, I tested the hypothesis that S. americana expresses locust-like density-dependent changes in behavior during both the first and final nymphal instars. I then compared the expression of behavioral phase change between S. americana and S. gregaria. First instar S. americana exhibited significant geographic variation in behavior with grasshoppers from a North Carolina population expressing more pronounced density-dependent changes relative to grasshoppers from a Texas population. The behavior of final instar S. americana was only slightly affected by rearing density and there was no evidence for a difference between populations. Comparison with S. gregaria revealed that the magnitude of density-dependent behavioral change, particularly among final instar nymphs, was much reduced in S. americana. Published by Elsevier Science Ltd.
Shigeyuki Koshikawa - One of the best experts on this subject based on the ideXlab platform.
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gene up regulation in response to predator kairomones in the water flea daphnia pulex
BMC Developmental Biology, 2010Co-Authors: Hitoshi Miyakawa, Asano Ishikawa, Naoki Sugimoto, Maki Imai, Yuki Ishikawa, Hidehiko Ishigaki, Yasukazu Okada, Satoshi Miyazaki, Shigeyuki KoshikawaAbstract:Numerous cases of predator-induced Polyphenisms, in which alternate phenotypes are produced in response to extrinsic stimuli, have been reported in aquatic taxa to date. The genus Daphnia (Branchiopoda, Cladocera) provides a model experimental system for the study of the developmental mechanisms and evolutionary processes associated with predator-induced Polyphenisms. In D. pulex, juveniles form neckteeth in response to predatory kairomones released by Chaoborus larvae (Insecta, Diptera).
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Caste-specific cytochrome P450 in the damp-wood termite Hodotermopsis sjostedti (Isoptera, Termopsidae).
Insect Molecular Biology, 2006Co-Authors: Richard Cornette, Tadao Matsumoto, Shigeyuki Koshikawa, Masaru Hojo, Toru MiuraAbstract:Termites are eusocial insects with a well-defined caste system, which is an example of Polyphenism. This Polyphenism is based on hormonally controlled differential gene expression. In the damp-wood termite Hodotermopsis sjostedti , we induced differentiation into the soldier caste by using juvenile hormone analogue treatment. We then investigated specific gene expression, which appeared during the hormonal response and triggered caste differentiation, using fluorescent differential display. A candidate cDNA sequence with similarity to cytochromes P450, CYP6AM1, was characterized and its transcript shown to be repressed between 1 and 3 days after hormone treatment. CYP6AM1 was specifically expressed in the fat body of pseudergates and soldiers. The putative function of this P450 is discussed with respect to the caste differentiation system.
Ehab Abouheif - One of the best experts on this subject based on the ideXlab platform.
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Interruption points in the wing gene regulatory network underlying wing Polyphenism evolved independently in male and female morphs in Cardiocondyla ants.
Journal of experimental zoology. Part B Molecular and developmental evolution, 2018Co-Authors: Jan Oettler, Tobias Platschek, Christine V. Schmidt, Rajendhran Rajakumar, Marie-julie Favé, Abderrahman Khila, Jürgen Heinze, Ehab AbouheifAbstract:Wing Polyphenism in ants, which produces a winged female queen caste and a wingless female worker caste, evolved approximately 150 million years ago and has been key to the remarkable success of ants. Approximately 20 million years ago, the myrmicine ant genus Cardiocondyla evolved an additional wing Polyphenism among males producing two male morphs: wingless males that fight to enhance mating success and winged males that disperse. Here we show that interruption of rudimentary wing-disc development in larvae of the ant Cardiocondyla obscurior occurs further downstream in the network in wingless males as compared with wingless female workers. This pattern is corroborated in C. kagutsuchi, a species from a different clade within the genus, indicating that late interruption of wing development in males is conserved across Cardiocondyla. Therefore, our results show that the novel male wing Polyphenism was not developmentally constrained by the pre-existing female wing Polyphenism and evolved through independent alteration of interruption points in the wing gene network. Furthermore, a comparison of adult morphological characters in C. obscurior reveals that developmental trajectories lead to similar morphological trait integration between winged and wingless females, but dramatically different integration between winged and wingless males. This suggests that the alternative sex-specific developmental routes to achieve winglessness in the genus Cardiocondyla may have evolved through different selection regimes acting on wingless males and females.
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The dynamics of developmental system drift in the gene network underlying wing Polyphenism in ants: a mathematical model.
Evolution & development, 2008Co-Authors: Marcos Nahmad, Leon Glass, Ehab AbouheifAbstract:SUMMARY Understanding the complex interaction between genotype and phenotype is a major challenge of Evolutionary Developmental Biology. One important facet of this complex interaction has been called ‘‘Developmental System Drift’’ (DSD). DSD occurs when a similar phenotype, which is homologous across a group of related species, is produced by different genes or gene expression patterns in each of these related species. We constructed a mathematical model to explore the developmental and evolutionary dynamics of DSD in the gene network underlying wing Polyphenism in ants. Wing Polyphenism in ants is the ability of an embryo to develop into a winged queen or a wingless worker in response to an environmental cue. Although wing Polyphenism is homologous across all ants, the gene network that underlies wing Polyphenism has evolved. In winged ant castes, our simulations reproduced the conserved gene expression patterns observed in the network that controls wing development in holometabolous insects. In wingless ant castes, we simulated the suppression of wings by interrupting (up- or downregulating) the expression of genes in the network. Our simulations uncovered the existence of four groups of genes that have similar effects on target gene expression and growth. Although each group is comprised of genes occupying different positions in the network, their interruption produces vestigial discs that are similar in size and shape. The implications of our results for understanding the origin, evolution, and dissociation of the gene network underlying wing Polyphenism in ants are discussed.
