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Morrow H, Mirth CK. Timing Drosophila development through steroid hormone action. Curr Opin Genet Dev 2024; 84:102148. [PMID: 38271845 DOI: 10.1016/j.gde.2023.102148] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2023] [Revised: 12/15/2023] [Accepted: 12/15/2023] [Indexed: 01/27/2024]
Abstract
Specifically timed pulses of the moulting hormone ecdysone are necessary for developmental progression in insects, guiding development through important milestones such as larval moults, pupation and metamorphosis. It also coordinates the acquisition of cell identities, known as cell patterning, and growth in a tissue-specific manner. In the absence of ecdysone, the ecdysone receptor heterodimer Ecdysone Receptor and Ultraspiracle represses expression of target primary response genes, which become de-repressed as the ecdysone titre rises. However, ecdysone signalling elicits both repressive and activating responses in a temporal and tissue-specific manner. To understand how ecdysone achieves such specificity, this review explores the layers of gene regulation involved in stage-appropriate ecdysone responses in Drosophila fruit flies.
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Affiliation(s)
- Hannah Morrow
- School of Biological Sciences, Monash University, Clayton, Victoria 3000, Australia.
| | - Christen K Mirth
- School of Biological Sciences, Monash University, Clayton, Victoria 3000, Australia
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2
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Vea IM, Wilcox AS, Frankino WA, Shingleton AW. Genetic Variation in Sexual Size Dimorphism Is Associated with Variation in Sex-Specific Plasticity in Drosophila. Am Nat 2023; 202:368-381. [PMID: 37606943 DOI: 10.1086/725420] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/23/2023]
Abstract
AbstractThe difference in body size between females and males, or sexual size dimorphism (SSD), is ubiquitous, yet we have a poor understanding of the developmental genetic mechanisms that generate it and how these mechanisms may vary within and among species. Such an understanding of the genetic architecture of SSD is important if we are to evaluate alternative models of SSD evolution, but the genetic architecture is difficult to describe because SSD is a characteristic of populations, not individuals. Here, we overcome this challenge by using isogenic lineages of Drosophila to measure SSD for 196 genotypes. We demonstrate extensive genetic variation for SSD, primarily driven by higher levels of genetic variation for body size among females than among males. While we observe a general increase in SSD with sex-averaged body size (pooling for sex) among lineages, most of the variation in SSD is independent of sex-averaged body size and shows a strong genetic correlation with sex-specific plasticity, such that increased female-biased SSD is associated with increased body size plasticity in females. Our data are consistent with the condition dependence hypothesis of sexual dimorphism and suggest that SSD in Drosophila is a consequence of selection on the developmental genetic mechanisms that regulate the plasticity of body size.
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One genome, multiple phenotypes: decoding the evolution and mechanisms of environmentally induced developmental plasticity in insects. Biochem Soc Trans 2023; 51:675-689. [PMID: 36929376 DOI: 10.1042/bst20210995] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Revised: 02/16/2023] [Accepted: 02/21/2023] [Indexed: 03/18/2023]
Abstract
Plasticity in developmental processes gives rise to remarkable environmentally induced phenotypes. Some of the most striking and well-studied examples of developmental plasticity are seen in insects. For example, beetle horn size responds to nutritional state, butterfly eyespots are enlarged in response to temperature and humidity, and environmental cues also give rise to the queen and worker castes of eusocial insects. These phenotypes arise from essentially identical genomes in response to an environmental cue during development. Developmental plasticity is taxonomically widespread, affects individual fitness, and may act as a rapid-response mechanism allowing individuals to adapt to changing environments. Despite the importance and prevalence of developmental plasticity, there remains scant mechanistic understanding of how it works or evolves. In this review, we use key examples to discuss what is known about developmental plasticity in insects and identify fundamental gaps in the current knowledge. We highlight the importance of working towards a fully integrated understanding of developmental plasticity in a diverse range of species. Furthermore, we advocate for the use of comparative studies in an evo-devo framework to address how developmental plasticity works and how it evolves.
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4
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Cobham AE, Neumann B, Mirth CK. Maintaining robust size across environmental conditions through plastic brain growth dynamics. Open Biol 2022; 12:220037. [PMID: 36102061 PMCID: PMC9471992 DOI: 10.1098/rsob.220037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Organ growth is tightly regulated across environmental conditions to generate an appropriate final size. While the size of some organs is free to vary, others need to maintain constant size to function properly. This poses a unique problem: how is robust final size achieved when environmental conditions alter key processes that regulate organ size throughout the body, such as growth rate and growth duration? While we know that brain growth is ‘spared’ from the effects of the environment from humans to fruit flies, we do not understand how this process alters growth dynamics across brain compartments. Here, we explore how this robustness in brain size is achieved by examining differences in growth patterns between the larval body, the brain and a brain compartment—the mushroom bodies—in Drosophila melanogaster across both thermal and nutritional conditions. We identify key differences in patterns of growth between the whole brain and mushroom bodies that are likely to underlie robustness of final organ shape. Further, we show that these differences produce distinct brain shapes across environments.
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Affiliation(s)
- Ansa E Cobham
- School of Biological Sciences, Monash University, Melbourne, Australia
| | - Brent Neumann
- Neuroscience Program, Monash Biomedicine Discovery Institute and Department of Anatomy and Developmental Biology, Monash University, Melbourne, Australia
| | - Christen K Mirth
- School of Biological Sciences, Monash University, Melbourne, Australia
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Nogueira Alves A, Oliveira MM, Koyama T, Shingleton A, Mirth CK. Ecdysone coordinates plastic growth with robust pattern in the developing wing. eLife 2022; 11:72666. [PMID: 35261337 PMCID: PMC8947767 DOI: 10.7554/elife.72666] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Accepted: 03/07/2022] [Indexed: 11/25/2022] Open
Abstract
Animals develop in unpredictable, variable environments. In response to environmental change, some aspects of development adjust to generate plastic phenotypes. Other aspects of development, however, are buffered against environmental change to produce robust phenotypes. How organ development is coordinated to accommodate both plastic and robust developmental responses is poorly understood. Here, we demonstrate that the steroid hormone ecdysone coordinates both plasticity of organ size and robustness of organ pattern in the developing wings of the fruit fly Drosophila melanogaster. Using fed and starved larvae that lack prothoracic glands, which synthesize ecdysone, we show that nutrition regulates growth both via ecdysone and via an ecdysone-independent mechanism, while nutrition regulates patterning only via ecdysone. We then demonstrate that growth shows a graded response to ecdysone concentration, while patterning shows a threshold response. Collectively, these data support a model where nutritionally regulated ecdysone fluctuations confer plasticity by regulating disc growth in response to basal ecdysone levels and confer robustness by initiating patterning only once ecdysone peaks exceed a threshold concentration. This could represent a generalizable mechanism through which hormones coordinate plastic growth with robust patterning in the face of environmental change.
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Affiliation(s)
| | | | | | - Alexander Shingleton
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, United States
| | - Christen K Mirth
- School of Biological Sciences, Monash University, Melbourne, Australia
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Tiwari P, Rengarajan H, Saunders TE. Scaling of internal organs during Drosophila embryonic development. Biophys J 2021; 120:4264-4276. [PMID: 34087212 PMCID: PMC8516638 DOI: 10.1016/j.bpj.2021.05.023] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 05/04/2021] [Accepted: 05/27/2021] [Indexed: 11/20/2022] Open
Abstract
Many species show a diverse range of sizes; for example, domestic dogs have large variation in body mass. Yet, the internal structure of the organism remains similar, i.e., the system scales to organism size. Drosophila melanogaster has been a powerful model system for exploring scaling mechanisms. In the early embryo, gene expression boundaries scale very precisely to embryo length. Later in development, the adult wings grow with remarkable symmetry and scale well with animal size. Yet, our knowledge of whether internal organs initially scale to embryo size remains largely unknown. Here, we utilize artificially small Drosophila embryos to explore how three critical internal organs-the heart, hindgut, and ventral nerve cord (VNC)-adapt to changes in embryo morphology. We find that the heart scales precisely with embryo length. Intriguingly, reduction in cardiac cell length, rather than number, appears to be important in controlling heart length. The hindgut, which is the first chiral organ to form, displays scaling with embryo size under large-scale changes in the artificially smaller embryos but shows few hallmarks of scaling within wild-type size variation. Finally, the VNC only displays weak scaling behavior; even large changes in embryo geometry result in only small shifts in VNC length. This suggests that the VNC may have an intrinsic minimal length that is largely independent of embryo length. Overall, our work shows that internal organs can adapt to embryo size changes in Drosophila, but the extent to which they scale varies significantly between organs.
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Affiliation(s)
- Prabhat Tiwari
- Mechanobiology Institute, National University of Singapore, Singapore, Singapore
| | | | - Timothy E Saunders
- Mechanobiology Institute, National University of Singapore, Singapore, Singapore; Department of Biological Sciences, National University of Singapore, Singapore, Singapore; Institute of Molecular and Cell Biology, A(∗)Star, Singapore, Singapore; Warwick Medical School, University of Warwick, Coventry, United Kingdom.
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7
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Sarikaya DP, Rickelton K, Cridland JM, Hatmaker R, Sheehy HK, Davis S, Khan N, Kochummen A, Begun DJ. Sex and tissue-specific evolution of developmental plasticity in Drosophila melanogaster. Ecol Evol 2021; 11:1334-1341. [PMID: 33598134 PMCID: PMC7863663 DOI: 10.1002/ece3.7136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Revised: 11/20/2020] [Accepted: 11/23/2020] [Indexed: 11/11/2022] Open
Abstract
Developmental plasticity influences the size of adult tissues in insects. Tissues can have unique responses to environmental perturbation during development; however, the prevalence of within species evolution of tissue-specific developmental plasticity remains unclear. To address this, we studied the effects of temperature and nutrition on wing and femur size in D. melanogaster populations from a temperate and tropical region. Wings were more sensitive to temperature, while wings and femurs were equally responsive to nutrition in both populations and sexes. The temperate population was larger under all conditions, except for femurs of starved females. In line with this, we observed greater femur size plasticity in response to starvation in temperate females, leading to differences in sexual dimorphism between populations such that the slope of the reaction norm of sexual dimorphism in the tropical population was double that of the temperate population. Lastly, we observed a significant trend for steeper slopes of reaction norms in temperate than in tropical females, but not in males. These findings highlight that plasticity divergence between populations can evolve heterogeneously across sexes and tissues and that nutritional plasticity can alter sexual dimorphism in D. melanogaster.
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Affiliation(s)
- Didem P. Sarikaya
- Evolution and EcologyUniversity of California DavisDavisCAUSA
- Molecular and Cellular BiologyUniversity of California DavisDavisCAUSA
| | | | | | - Ryan Hatmaker
- Evolution and EcologyUniversity of California DavisDavisCAUSA
| | | | - Sophia Davis
- Evolution and EcologyUniversity of California DavisDavisCAUSA
| | - Nossin Khan
- Evolution and EcologyUniversity of California DavisDavisCAUSA
| | | | - David J. Begun
- Evolution and EcologyUniversity of California DavisDavisCAUSA
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Mirth CK, Saunders TE, Amourda C. Growing Up in a Changing World: Environmental Regulation of Development in Insects. ANNUAL REVIEW OF ENTOMOLOGY 2021; 66:81-99. [PMID: 32822557 DOI: 10.1146/annurev-ento-041620-083838] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
All organisms are exposed to changes in their environment throughout their life cycle. When confronted with these changes, they adjust their development and physiology to ensure that they can produce the functional structures necessary for survival and reproduction. While some traits are remarkably invariant, or robust, across environmental conditions, others show high degrees of variation, known as plasticity. Generally, developmental processes that establish cell identity are thought to be robust to environmental perturbation, while those relating to body and organ growth show greater degrees of plasticity. However, examples of plastic patterning and robust organ growth demonstrate that this is not a hard-and-fast rule.In this review, we explore how the developmental context and the gene regulatory mechanisms underlying trait formation determine the impacts of the environment on development in insects. Furthermore, we outline future issues that need to be resolved to understand how the structure of signaling networks defines whether a trait displays plasticity or robustness.
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Affiliation(s)
- Christen K Mirth
- School of Biological Sciences, Monash University, Melbourne 3800, Victoria, Australia;
| | - Timothy E Saunders
- Mechanobiology Institute, National University of Singapore, Singapore 117411, Republic of Singapore
- Department of Biological Sciences, National University of Singapore, Singapore 117588, Republic of Singapore
- Institute of Molecular and Cell Biology, A*Star, Proteos, Singapore 138673, Republic of Singapore
| | - Christopher Amourda
- MRC London Institute of Medical Sciences, Imperial College London, London W12 0NN, United Kingdom
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Abstract
Abstract
Background
Organisms show an incredibly diverse array of body and organ shapes that are both unique to their taxon and important for adapting to their environment. Achieving these specific shapes involves coordinating the many processes that transform single cells into complex organs, and regulating their growth so that they can function within a fully-formed body.
Main text
Conceptually, body and organ shape can be separated in two categories, although in practice these categories need not be mutually exclusive. Body shape results from the extent to which organs, or parts of organs, grow relative to each other. The patterns of relative organ size are characterized using allometry. Organ shape, on the other hand, is defined as the geometric features of an organ’s component parts excluding its size. Characterization of organ shape is frequently described by the relative position of homologous features, known as landmarks, distributed throughout the organ. These descriptions fall into the domain of geometric morphometrics.
Conclusion
In this review, we discuss the methods of characterizing body and organ shape, the developmental programs thought to underlie each, highlight when and how the mechanisms regulating body and organ shape might overlap, and provide our perspective on future avenues of research.
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McKenna KZ, Tao D, Nijhout HF. Exploring the Role of Insulin Signaling in Relative Growth: A Case Study on Wing-Body Scaling in Lepidoptera. Integr Comp Biol 2019; 59:1324-1337. [DOI: 10.1093/icb/icz080] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Abstract
Adult forms emerge from the relative growth of the body and its parts. Each appendage and organ has a unique pattern of growth that influences the size and shape it attains. This produces adult size relationships referred to as static allometries, which have received a great amount of attention in evolutionary and developmental biology. However, many questions remain unanswered, for example: What sorts of developmental processes coordinate growth? And how do these processes change given variation in body size? It has become increasingly clear that nutrition is one of the strongest influences on size relationships. In insects, nutrition acts via insulin/TOR signaling to facilitate inter- and intra-specific variation in body size and appendage size. Yet, the mechanism by which insulin signaling influences the scaling of growth remains unclear. Here we will discuss the potential roles of insulin signaling in wing-body scaling in Lepidoptera. We analyzed the growth of wings in animals reared on different diet qualities that induce a range of body sizes not normally present in our laboratory populations. By growing wings in tissue culture, we survey how perturbation and stimulation of insulin/TOR signaling influences wing growth. To conclude, we will discuss the implications of our findings for the development and evolution of organismal form.
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Affiliation(s)
| | - Della Tao
- Department of Biology, Duke University, Durham, NC 27708, USA
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