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Zhang Z, Liu X, Yu Y, Yang F, Li K. The receptor tyrosine kinase torso regulates ecdysone homeostasis to control developmental timing in Bombyx mori. INSECT SCIENCE 2021; 28:1582-1590. [PMID: 33205532 PMCID: PMC9291747 DOI: 10.1111/1744-7917.12879] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/21/2020] [Revised: 09/11/2020] [Accepted: 09/24/2020] [Indexed: 06/11/2023]
Abstract
Insect growth and development are precisely controlled by hormone homeostasis. The prothoracicotropic hormone (PTTH) receptor, Torso, is a member of the receptor tyrosine kinase family in insects. Activation of Torso by PTTH triggers biosynthesis and release of the steroid hormone in the prothoracic gland (PG). Although numbers of genes functioning in steroid hormone synthesis and metabolism have been identified in insects, the PTTH transduction pathway via its receptor Torso is poorly understood. In the current study, we describe a loss-of-function analysis of Torso in the silkworm, Bombyx mori, by targeted gene disruption using the transgenic CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/RNA-guided Cas9 nucleases) system. Depletion of B. mori Torso (BmTorso) did not eventually affect larval ecdysis and metamorphosis processes. Instead, BmTorso deficiency resulted in significant extension of developing time during larval and pupal stages with increased pupa and cocoon sizes. The ecdysteriod titers in the hemolymph of BmTorso mutants sharpy declined. Transcriptional levels of genes involved in ecdysone biosynthesis and ecdysteroid signaling pathways were significantly reduced in BmTorso-deficient animals. Additionally, RNA-Seq analysis revealed that genes involved in the longevity pathway and protein processing in the endoplasmic reticulum pathway were affected after BmTorso deletion. These results indicate that Torso is critical for maintaining steroid hormone homeostasis in insects.
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Affiliation(s)
- Zhong‐Jie Zhang
- School of Life ScienceEast China Normal UniversityShanghai200062China
- Key Laboratory of Insect Developmental and Evolutionary BiologyCenter for Excellence in Molecular Plant SciencesShanghai Institute of Plant Physiology and EcologyChinese Academy of SciencesShanghai200032China
- CAS Center for Excellence in Biotic InteractionsUniversity of Chinese Academy of SciencesBeijing100049China
| | - Xiao‐Jing Liu
- Key Laboratory of Insect Developmental and Evolutionary BiologyCenter for Excellence in Molecular Plant SciencesShanghai Institute of Plant Physiology and EcologyChinese Academy of SciencesShanghai200032China
- CAS Center for Excellence in Biotic InteractionsUniversity of Chinese Academy of SciencesBeijing100049China
| | - Ye Yu
- Key Laboratory of Insect Developmental and Evolutionary BiologyCenter for Excellence in Molecular Plant SciencesShanghai Institute of Plant Physiology and EcologyChinese Academy of SciencesShanghai200032China
- CAS Center for Excellence in Biotic InteractionsUniversity of Chinese Academy of SciencesBeijing100049China
| | - Fang‐Ying Yang
- Key Laboratory of Insect Developmental and Evolutionary BiologyCenter for Excellence in Molecular Plant SciencesShanghai Institute of Plant Physiology and EcologyChinese Academy of SciencesShanghai200032China
- CAS Center for Excellence in Biotic InteractionsUniversity of Chinese Academy of SciencesBeijing100049China
| | - Kai Li
- School of Life ScienceEast China Normal UniversityShanghai200062China
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Barredo CG, Gil-Marti B, Deveci D, Romero NM, Martin FA. Timing the Juvenile-Adult Neurohormonal Transition: Functions and Evolution. Front Endocrinol (Lausanne) 2020; 11:602285. [PMID: 33643219 PMCID: PMC7909313 DOI: 10.3389/fendo.2020.602285] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Accepted: 12/28/2020] [Indexed: 02/05/2023] Open
Abstract
Puberty and metamorphosis are two major developmental transitions linked to the reproductive maturation. In mammals and vertebrates, the central brain acts as a gatekeeper, timing the developmental transition through the activation of a neuroendocrine circuitry. In addition to reproduction, these neuroendocrine axes and the sustaining genetic network play additional roles in metabolism, sleep and behavior. Although neurohormonal axes regulating juvenile-adult transition have been classically considered the result of convergent evolution (i.e., analogous) between mammals and insects, recent findings challenge this idea, suggesting that at least some neuroendocrine circuits might be present in the common bilaterian ancestor Urbilateria. The initial signaling pathways that trigger the transition in different species appear to be of a single evolutionary origin and, consequently, many of the resulting functions are conserved with a few other molecular players being co-opted during evolution.
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Affiliation(s)
- Celia G. Barredo
- Molecular Physiology of Behavior Laboratory, Department of Molecular, Cellular and Developmental Neurobiology, Cajal Institute, Spanish National Research Council (CSIC), Madrid, Spain
| | - Beatriz Gil-Marti
- Molecular Physiology of Behavior Laboratory, Department of Molecular, Cellular and Developmental Neurobiology, Cajal Institute, Spanish National Research Council (CSIC), Madrid, Spain
| | - Derya Deveci
- Sartorius Netherlands BV, Amersfoor, Netherlands
| | - Nuria M. Romero
- Developmental Timing, Environment and Behaviors Laboratory, Institut Sophia Agrobiotech, Université Côte d’Azur-INRAE-CNRS-INSERM, Sophia Antipolis, France
- *Correspondence: Nuria M. Romero, ; Francisco A. Martin,
| | - Francisco A. Martin
- Molecular Physiology of Behavior Laboratory, Department of Molecular, Cellular and Developmental Neurobiology, Cajal Institute, Spanish National Research Council (CSIC), Madrid, Spain
- *Correspondence: Nuria M. Romero, ; Francisco A. Martin,
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Shimell M, Pan X, Martin FA, Ghosh AC, Leopold P, O'Connor MB, Romero NM. Prothoracicotropic hormone modulates environmental adaptive plasticity through the control of developmental timing. Development 2018; 145:dev.159699. [PMID: 29467242 DOI: 10.1242/dev.159699] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Accepted: 02/12/2018] [Indexed: 12/19/2022]
Abstract
Adult size and fitness are controlled by a combination of genetics and environmental cues. In Drosophila, growth is confined to the larval phase and final body size is impacted by the duration of this phase, which is under neuroendocrine control. The neuropeptide prothoracicotropic hormone (PTTH) has been proposed to play a central role in controlling the length of the larval phase through regulation of ecdysone production, a steroid hormone that initiates larval molting and metamorphosis. Here, we test this by examining the consequences of null mutations in the Ptth gene for Drosophila development. Loss of Ptth causes several developmental defects, including a delay in developmental timing, increase in critical weight, loss of coordination between body and imaginal disc growth, and reduced adult survival in suboptimal environmental conditions such as nutritional deprivation or high population density. These defects are caused by a decrease in ecdysone production associated with altered transcription of ecdysone biosynthetic genes. Therefore, the PTTH signal contributes to coordination between environmental cues and the developmental program to ensure individual fitness and survival.
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Affiliation(s)
- MaryJane Shimell
- Department of Genetics Cell Biology and Development, University of Minnesota, Minneapolis, MN 55455, USA
| | - Xueyang Pan
- Department of Genetics Cell Biology and Development, University of Minnesota, Minneapolis, MN 55455, USA
| | - Francisco A Martin
- University Côte d'Azur, CNRS, Inserm, Institute of Biology Valrose, Parc Valrose, 06108 Nice, France.,Cajal Institute, Av Doctor Arce 37, 28002 Madrid, Spain
| | - Arpan C Ghosh
- Department of Genetics Cell Biology and Development, University of Minnesota, Minneapolis, MN 55455, USA
| | - Pierre Leopold
- University Côte d'Azur, CNRS, Inserm, Institute of Biology Valrose, Parc Valrose, 06108 Nice, France
| | - Michael B O'Connor
- Department of Genetics Cell Biology and Development, University of Minnesota, Minneapolis, MN 55455, USA
| | - Nuria M Romero
- University Côte d'Azur, CNRS, Inserm, Institute of Biology Valrose, Parc Valrose, 06108 Nice, France
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Xu QY, Meng QW, Deng P, Guo WC, Li GQ. Leptinotarsa hormone receptor 4 (HR4) tunes ecdysteroidogenesis and mediates 20-hydroxyecdysone signaling during larval-pupal metamorphosis. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2018; 94:50-60. [PMID: 28951206 DOI: 10.1016/j.ibmb.2017.09.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Revised: 09/20/2017] [Accepted: 09/21/2017] [Indexed: 06/07/2023]
Abstract
Hormone receptor 4 (HR4) is involved in the regulation of 20-hydroxyecdysone (20E) biosynthesis and the mediation of 20E signaling during larval-pupal transition in a holometabolan Drosophila melanogaster, whereas it acts as a repressor in 20E-responsive transcriptional cascade in a hemimetabolan, Blattella germanica. Here we characterized two HR4 splicing variants, LdHR4X1 and LdHR4X2, in a coleopteran Leptinotarsa decemlineata. LdHR4X1 was highly expressed in the prothoracic gland and epidermis while LdHR4X2 was abundantly transcribed in the nervous system. In vivo results showed that both prothoracicotropic hormone and 20E pathways transcriptionally regulated LdHR4, in an isoform-dependent pattern. RNA interference of LdHR4 at the final (fourth) larval instar, in contrast to the second- and third-instar periods, enhanced the expression of two ecdysteroidogenesis genes, increased 20E titer, upregulated transcription of five 20E-response genes, and reduced the mRNA level of Fushi tarazu-factor 1 (FTZ-F1). As a result, the fourth-instar LdHR4 RNAi larvae exhibited accelerated development and reduced body weight. Moreover, knockdown of LdHR4 at the fourth instar resulted in larval lethality and impaired pupation. Feeding of pyriproxyfen (a mimic of juvenile hormone) or silencing of a juvenile hormone degrading enzyme gene restored the normal course of ecdysteroidogenesis, duration of larval development, and body weight in fourth-instar LdHR4 RNAi larvae. The treatment partially suppressed the larval mortality but not the failure to pupate. The dual role of HR4 during larval-pupal metamorphosis appears to be evolutionarily conserved among holometabolans.
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Affiliation(s)
- Qing-Yu Xu
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China.
| | - Qing-Wei Meng
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China.
| | - Pan Deng
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China.
| | - Wen-Chao Guo
- Department of Plant Protection, Xinjiang Academy of Agricultural Sciences, Urumqi 830091, China.
| | - Guo-Qing Li
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China.
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Niwa R, Niwa YS. Enzymes for ecdysteroid biosynthesis: their biological functions in insects and beyond. Biosci Biotechnol Biochem 2014; 78:1283-92. [DOI: 10.1080/09168451.2014.942250] [Citation(s) in RCA: 131] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Abstract
Steroid hormones are responsible for the coordinated regulation of many aspects of biological processes in multicellular organisms. Since the last century, many studies have identified and characterized steroidogenic enzymes in vertebrates, including mammals. However, much less is known about invertebrate steroidogenic enzymes. In the last 15 years, a number of steroidogenic enzymes and their functions have been characterized in ecdysozoan animals, especially in the fruit fly Drosophila melanogaster. In this review, we summarize the latest knowledge of enzymes crucial for synthesizing ecdysteroids, the principal insect steroid hormones. We also discuss the functional conservation and diversity of ecdysteroidogenic enzymes in other insects and even non-insect species, such as nematodes, vertebrates, and lower eukaryotes.
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Affiliation(s)
- Ryusuke Niwa
- Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
- Japan Science and Technology Agency, PRESTO, Kawaguchi, Japan
| | - Yuko S Niwa
- Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
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Nuclear receptors in nematode development: Natural experiments made by a phylum. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2014; 1849:224-37. [PMID: 24984201 DOI: 10.1016/j.bbagrm.2014.06.016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Revised: 06/21/2014] [Accepted: 06/23/2014] [Indexed: 11/21/2022]
Abstract
The development of complex multicellular organisms is dependent on regulatory decisions that are necessary for the establishment of specific differentiation and metabolic cellular states. Nuclear receptors (NRs) form a large family of transcription factors that play critical roles in the regulation of development and metabolism of Metazoa. Based on their DNA binding and ligand binding domains, NRs are divided into eight NR subfamilies from which representatives of six subfamilies are present in both deuterostomes and protostomes indicating their early evolutionary origin. In some nematode species, especially in Caenorhabditis, the family of NRs expanded to a large number of genes strikingly exceeding the number of NR genes in vertebrates or insects. Nematode NRs, including the multiplied Caenorhabditis genes, show clear relation to vertebrate and insect homologues belonging to six of the eight main NR subfamilies. This review summarizes advances in research of nematode NRs and their developmental functions. Nematode NRs can reveal evolutionarily conserved mechanisms that regulate specific developmental and metabolic processes as well as new regulatory adaptations. They represent the results of a large number of natural experiments with structural and functional potential of NRs for the evolution of the phylum. The conserved and divergent character of nematode NRs adds a new dimension to our understanding of the general biology of regulation by NRs. This article is part of a Special Issue entitled: Nuclear receptors in animal development.
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Good RT, Gramzow L, Battlay P, Sztal T, Batterham P, Robin C. The molecular evolution of cytochrome P450 genes within and between drosophila species. Genome Biol Evol 2014; 6:1118-34. [PMID: 24751979 PMCID: PMC4040991 DOI: 10.1093/gbe/evu083] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
We map 114 gene gains and 74 gene losses in the P450 gene family across the phylogeny of 12 Drosophila species by examining the congruence of gene trees and species trees. Although the number of P450 genes varies from 74 to 94 in the species examined, we infer that there were at least 77 P450 genes in the ancestral Drosophila genome. One of the most striking observations in the data set is the elevated loss of P450 genes in the Drosophila sechellia lineage. The gain and loss events are not evenly distributed among the P450 genes-with 30 genes showing no gene gains or losses whereas others show as many as 20 copy number changes among the species examined. The P450 gene clades showing the fewest number of gene gain and loss events tend to be those evolving with the most purifying selection acting on the protein sequences, although there are exceptions, such as the rapid rate of amino acid replacement observed in the single copy phantom (Cyp306a1) gene. Within D. melanogaster, we observe gene copy number polymorphism in ten P450 genes including multiple cases of interparalog chimeras. Nonallelic homologous recombination (NAHR) has been associated with deleterious mutations in humans, but here we provide a second possible example of an NAHR event in insect P450s being adaptive. Specifically, we find that a polymorphic Cyp12a4/Cyp12a5 chimera correlates with resistance to an insecticide. Although we observe such interparalog exchange in our within-species data sets, we have little evidence of it between species, raising the possibility that such events may occur more frequently than appreciated but are masked by subsequent sequence change.
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Affiliation(s)
- Robert T Good
- Department of Genetics, University of Melbourne, AustraliaPresent address: Department of Genetics, Friedrich Schiller University Jena, Philosophenweg 12, Jena, GermanyPresent address: School of Biological Sciences, Monash University, Australia
| | - Lydia Gramzow
- Present address: Department of Genetics, Friedrich Schiller University Jena, Philosophenweg 12, Jena, Germany
| | - Paul Battlay
- Department of Genetics, University of Melbourne, AustraliaPresent address: Department of Genetics, Friedrich Schiller University Jena, Philosophenweg 12, Jena, GermanyPresent address: School of Biological Sciences, Monash University, Australia
| | - Tamar Sztal
- Present address: School of Biological Sciences, Monash University, Australia
| | - Philip Batterham
- Department of Genetics, University of Melbourne, AustraliaPresent address: Department of Genetics, Friedrich Schiller University Jena, Philosophenweg 12, Jena, GermanyPresent address: School of Biological Sciences, Monash University, Australia
| | - Charles Robin
- Department of Genetics, University of Melbourne, AustraliaPresent address: Department of Genetics, Friedrich Schiller University Jena, Philosophenweg 12, Jena, GermanyPresent address: School of Biological Sciences, Monash University, Australia
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Pondeville E, David JP, Guittard E, Maria A, Jacques JC, Ranson H, Bourgouin C, Dauphin-Villemant C. Microarray and RNAi analysis of P450s in Anopheles gambiae male and female steroidogenic tissues: CYP307A1 is required for ecdysteroid synthesis. PLoS One 2013; 8:e79861. [PMID: 24324583 PMCID: PMC3851169 DOI: 10.1371/journal.pone.0079861] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Accepted: 09/24/2013] [Indexed: 11/26/2022] Open
Abstract
In insects, the steroid hormone 20-hydroxyecdysone (20E) coordinates major developmental transitions. While the first and the final steps of 20E biosynthesis are characterized, the pathway from 7-dehydrocholesterol to 5β-ketodiol, commonly referred as the “black box”, remains hypothetical and whether there are still unidentified enzymes is unknown. The black box would include some oxidative steps, which are believed to be mediated by P450 enzymes. To identify new enzyme(s) involved in steroid synthesis, we analyzed by small-scale microarray the expression of all the genes encoding P450 enzymes of the malaria mosquito Anopheles gambiae in active steroidogenic organs of adults, ovaries from blood-fed females and male reproductive tracts, compared to inactive steroidogenic organs, ovaries from non-blood-fed females. Some genes encoding P450 enzymes were specifically overexpressed in female ovaries after a blood-meal or in male reproductive tracts but only three genes were found to be overexpressed in active steroidogenic organs of both females and males: cyp307a1, cyp4g16 and cyp6n1. Among these genes, only cyp307a1 has an expression pattern similar to other mosquito steroidogenic genes. Moreover, loss-of-function by transient RNAi targeting cyp307a1 disrupted ecdysteroid production demonstrating that this gene is required for ecdysteroid biosynthesis in Anopheles gambiae.
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Affiliation(s)
- Emilie Pondeville
- Biogenèse des Stéroïdes, FRE2852, CNRS-UPMC, Paris, France
- Unit of Insect Vector Genetics and Genomics, Department of Parasitology and Mycology, CNRS Unit URA3012: Hosts, Vectors and Infectious Agents, Institut Pasteur, Paris, France
- * E-mail:
| | - Jean-Philippe David
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
- Laboratoire d'Ecologie Alpine, UMR 5553, CNRS-Université de Grenoble, Grenoble, France
| | | | - Annick Maria
- Biogenèse des Stéroïdes, FRE2852, CNRS-UPMC, Paris, France
| | - Jean-Claude Jacques
- Centre de Production et d'Infection des Anophèles, Institut Pasteur, Paris, France
| | - Hilary Ranson
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Catherine Bourgouin
- Unit of Insect Vector Genetics and Genomics, Department of Parasitology and Mycology, CNRS Unit URA3012: Hosts, Vectors and Infectious Agents, Institut Pasteur, Paris, France
- Centre de Production et d'Infection des Anophèles, Institut Pasteur, Paris, France
| | - Chantal Dauphin-Villemant
- Biogenèse des Stéroïdes, FRE2852, CNRS-UPMC, Paris, France
- Department of Ecology and Evolution, Université de Lausanne, Lausanne, Suisse
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Moeller ME, Danielsen ET, Herder R, O'Connor MB, Rewitz KF. Dynamic feedback circuits function as a switch for shaping a maturation-inducing steroid pulse in Drosophila. Development 2013; 140:4730-9. [PMID: 24173800 DOI: 10.1242/dev.099739] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Steroid hormones trigger the onset of sexual maturation in animals by initiating genetic response programs that are determined by steroid pulse frequency, amplitude and duration. Although steroid pulses coordinate growth and timing of maturation during development, the mechanisms generating these pulses are not known. Here we show that the ecdysone steroid pulse that drives the juvenile-adult transition in Drosophila is determined by feedback circuits in the prothoracic gland (PG), the major steroid-producing tissue of insect larvae. These circuits coordinate the activation and repression of hormone synthesis, the two key parameters determining pulse shape (amplitude and duration). We show that ecdysone has a positive-feedback effect on the PG, rapidly amplifying its own synthesis to trigger pupariation as the onset of maturation. During the prepupal stage, a negative-feedback signal ensures the decline in ecdysone levels required to produce a temporal steroid pulse that drives developmental progression to adulthood. The feedback circuits rely on a developmental switch in the expression of Broad isoforms that transcriptionally activate or silence components in the ecdysone biosynthetic pathway. Remarkably, our study shows that the same well-defined genetic program that stimulates a systemic downstream response to ecdysone is also utilized upstream to set the duration and amplitude of the ecdysone pulse. Activation of this switch-like mechanism ensures a rapid, self-limiting PG response that functions in producing steroid oscillations that can guide the decision to terminate growth and promote maturation.
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Affiliation(s)
- Morten E Moeller
- Department of Biology, University of Copenhagen, 2100 Copenhagen, Denmark
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Danielsen ET, Moeller ME, Rewitz KF. Nutrient Signaling and Developmental Timing of Maturation. Curr Top Dev Biol 2013; 105:37-67. [DOI: 10.1016/b978-0-12-396968-2.00002-6] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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Rewitz KF, Yamanaka N, O'Connor MB. Developmental checkpoints and feedback circuits time insect maturation. Curr Top Dev Biol 2013; 103:1-33. [PMID: 23347514 DOI: 10.1016/b978-0-12-385979-2.00001-0] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The transition from juvenile to adult is a fundamental process that allows animals to allocate resource toward reproduction after completing a certain amount of growth. In insects, growth to a species-specific target size induces pulses of the steroid hormone ecdysone that triggers metamorphosis and reproductive maturation. The past few years have seen significant progress in understanding the interplay of mechanisms that coordinate timing of ecdysone production and release. These studies show that the neuroendocrine system monitors complex size-related and nutritional signals, as well as external cues, to time production and release of ecdysone. Based on results discussed here, we suggest that developmental progression to adulthood is controlled by checkpoints that regulate the genetic timing program enabling it to adapt to different environmental conditions. These checkpoints utilize a number of signaling pathways to modulate ecdysone production in the prothoracic gland. Release of ecdysone activates an autonomous cascade of both feedforward and feedback signals that determine the duration of the ecdysone pulse at each developmental transitions. Conservation of the genetic mechanisms that coordinate the juvenile-adult transition suggests that insights from the fruit fly Drosophila will provide a framework for future investigation of developmental timing in metazoans.
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Affiliation(s)
- Kim F Rewitz
- Department of Biology, Cell and Neurobiology, University of Copenhagen, Copenhagen, Denmark.
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