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Clark E, Battistara M, Benton MA. A timer gene network is spatially regulated by the terminal system in the Drosophila embryo. eLife 2022; 11:e78902. [PMID: 36524728 PMCID: PMC10065802 DOI: 10.7554/elife.78902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Accepted: 12/15/2022] [Indexed: 12/23/2022] Open
Abstract
In insect embryos, anteroposterior patterning is coordinated by the sequential expression of the 'timer' genes caudal, Dichaete, and odd-paired, whose expression dynamics correlate with the mode of segmentation. In Drosophila, the timer genes are expressed broadly across much of the blastoderm, which segments simultaneously, but their expression is delayed in a small 'tail' region, just anterior to the hindgut, which segments during germband extension. Specification of the tail and the hindgut depends on the terminal gap gene tailless, but beyond this the regulation of the timer genes is poorly understood. We used a combination of multiplexed imaging, mutant analysis, and gene network modelling to resolve the regulation of the timer genes, identifying 11 new regulatory interactions and clarifying the mechanism of posterior terminal patterning. We propose that a dynamic Tailless expression gradient modulates the intrinsic dynamics of a timer gene cross-regulatory module, delineating the tail region and delaying its developmental maturation.
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Affiliation(s)
- Erik Clark
- Department of Zoology, University of CambridgeCambridgeUnited Kingdom
- Department of Systems Biology, Harvard Medical SchoolBostonUnited States
- Department of Genetics, University of CambridgeCambridgeUnited Kingdom
| | - Margherita Battistara
- Department of Zoology, University of CambridgeCambridgeUnited Kingdom
- Department of Physiology, Development and Neuroscience, University of CambridgeCambridgeUnited Kingdom
| | - Matthew A Benton
- Department of Zoology, University of CambridgeCambridgeUnited Kingdom
- Developmental Biology Unit, EMBLHeidelbergGermany
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2
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Lin GW, Chung CY, Cook CE, Lin MD, Lee WC, Chang CC. Germline specification and axis determination in viviparous and oviparous pea aphids: conserved and divergent features. Dev Genes Evol 2022; 232:51-65. [PMID: 35678925 PMCID: PMC9329388 DOI: 10.1007/s00427-022-00690-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Accepted: 05/19/2022] [Indexed: 01/06/2023]
Abstract
Aphids are hemimetabolous insects that undergo incomplete metamorphosis without pupation. The annual life cycle of most aphids includes both an asexual (viviparous) and a sexual (oviparous) phase. Sexual reproduction only occurs once per year and is followed by many generations of asexual reproduction, during which aphids propagate exponentially with telescopic development. Here, we discuss the potential links between viviparous embryogenesis and derived developmental features in the pea aphid Acyrthosiphon pisum, particularly focusing on germline specification and axis determination, both of which are key events of early development in insects. We also discuss potential evolutionary paths through which both viviparous and oviparous females might have come to utilize maternal germ plasm to drive germline specification. This developmental strategy, as defined by germline markers, has not been reported in other hemimetabolous insects. In viviparous females, furthermore, we discuss whether molecules that in other insects characterize germ plasm, like Vasa, also participate in posterior determination and how the anterior localization of the hunchback orthologue Ap-hb establishes the anterior-posterior axis. We propose that the linked chain of developing oocytes and embryos within each ovariole and the special morphology of early embryos might have driven the formation of evolutionary novelties in germline specification and axis determination in the viviparous aphids. Moreover, based upon the finding that the endosymbiont Buchnera aphidicola is closely associated with germ cells throughout embryogenesis, we propose presumptive roles for B. aphidicola in aphid development, discussing how it might regulate germline migration in both reproductive modes of pea aphids. In summary, we expect that this review will shed light on viviparous as well as oviparous development in aphids.
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Affiliation(s)
- Gee-Way Lin
- Laboratory for Genomics and Development, College of Bio-Resources and Agriculture, Department of Entomology, National Taiwan University (NTU), No. 1, Sec. 4, Roosevelt Rd., Taipei, 10617, Taiwan
- Department of Biochemistry and Molecular Cell Biology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
| | - Chen-Yo Chung
- Laboratory for Genomics and Development, College of Bio-Resources and Agriculture, Department of Entomology, National Taiwan University (NTU), No. 1, Sec. 4, Roosevelt Rd., Taipei, 10617, Taiwan
- Research Center for Developmental Biology and Regenerative Medicine, NTU, Taipei, Taiwan
| | - Charles E Cook
- Laboratory for Genomics and Development, College of Bio-Resources and Agriculture, Department of Entomology, National Taiwan University (NTU), No. 1, Sec. 4, Roosevelt Rd., Taipei, 10617, Taiwan
| | - Ming-Der Lin
- Department of Molecular Biology and Human Genetics, Tzu Chi University, Hualien, Taiwan
| | - Wen-Chih Lee
- Research Center for Global SDGs Challenges, Office of Research and Development, Tzu Chi University, Hualien, Taiwan
| | - Chun-Che Chang
- Laboratory for Genomics and Development, College of Bio-Resources and Agriculture, Department of Entomology, National Taiwan University (NTU), No. 1, Sec. 4, Roosevelt Rd., Taipei, 10617, Taiwan.
- Research Center for Developmental Biology and Regenerative Medicine, NTU, Taipei, Taiwan.
- Institute of Biotechnology, College of Bio-Resources and Agriculture, NTU, Taipei, Taiwan.
- Genome and Systems Biology Degree Program, NTU, Taipei, Taiwan.
- International Graduate Program of Molecular Science and Technology, NTU, Taipei, Taiwan.
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3
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Schmidt-Ott U, Yoon Y. Evolution and loss of ß-catenin and TCF-dependent axis specification in insects. CURRENT OPINION IN INSECT SCIENCE 2022; 50:100877. [PMID: 35104659 PMCID: PMC9133022 DOI: 10.1016/j.cois.2022.100877] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Revised: 01/06/2022] [Accepted: 01/11/2022] [Indexed: 06/14/2023]
Abstract
Mechanisms and evolution of primary axis specification in insects are discussed in the context of the roles of ß-catenin and TCF in polarizing metazoan embryos. Three hypotheses are presented. First, insects with sequential segmentation and posterior growth use cell-autonomous mechanisms for establishing embryo polarity via the nuclear ratio of ß-catenin and TCF. Second, TCF homologs establish competence for anterior specification. Third, the evolution of simultaneous segmentation mechanisms, also known as long-germ development, resulted in primary axis specification mechanisms that are independent of ß-catenin but reliant on TCF, a condition that preceded the frequent replacement of anterior determinants in long germ insects.
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Affiliation(s)
- Urs Schmidt-Ott
- University of Chicago, Dept. of Organismal Biology and Anatomy, 1027 East 57th Street, Chicago, IL 60637, USA.
| | - Yoseop Yoon
- University of California, Irvine, Dept. of Microbiology and Molecular Genetics, School of Medicine, 811 Health Sciences Rd., Med Sci B262, CA 92617, USA
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4
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Taylor SE, Dearden PK. The Nasonia pair-rule gene regulatory network retains its function over 300 million years of evolution. Development 2022; 149:dev199632. [PMID: 35142336 PMCID: PMC8959145 DOI: 10.1242/dev.199632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Accepted: 01/28/2022] [Indexed: 11/20/2022]
Abstract
Insect segmentation is a well-studied and tractable system with which to investigate the genetic regulation of development. Though insects segment their germband using a variety of methods, modelling work implies that a single gene regulatory network can underpin the two main types of insect segmentation. This means limited genetic changes are required to explain significant differences in segmentation mode between different insects. This idea needs to be tested in a wider variety of species, and the nature of the gene regulatory network (GRN) underlying this model has not been tested. Some insects, e.g. Nasonia vitripennis and Apis mellifera segment progressively, a pattern not examined in previous studies of this segmentation model, producing stripes at different times progressively through the embryo, but not from a segment addition zone. Here, we aim to understand the GRNs patterning Nasonia using a simulation-based approach. We found that an existing model of Drosophila segmentation ( Clark, 2017) can be used to recapitulate the progressive segmentation of Nasonia, if provided with altered inputs in the form of expression of the timer genes Nv-caudal and Nv-odd paired. We predict limited topological changes to the pair-rule network and show, by RNAi knockdown, that Nv-odd paired is required for morphological segmentation. Together this implies that very limited changes to the Drosophila network are required to simulate Nasonia segmentation, despite significant differences in segmentation modes, implying that Nasonia use a very similar version of an ancestral GRN used by Drosophila, which must therefore have been conserved for at least 300 million years.
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Affiliation(s)
| | - Peter K. Dearden
- Genomics Aotearoa and Department of Biochemistry, University of Otago, PO Box 56, Dunedin 9016, Aotearoa-New Zealand
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5
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Diaz-Cuadros M, Pourquié O, El-Sherif E. Patterning with clocks and genetic cascades: Segmentation and regionalization of vertebrate versus insect body plans. PLoS Genet 2021; 17:e1009812. [PMID: 34648490 PMCID: PMC8516289 DOI: 10.1371/journal.pgen.1009812] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Oscillatory and sequential processes have been implicated in the spatial patterning of many embryonic tissues. For example, molecular clocks delimit segmental boundaries in vertebrates and insects and mediate lateral root formation in plants, whereas sequential gene activities are involved in the specification of regional identities of insect neuroblasts, vertebrate neural tube, vertebrate limb, and insect and vertebrate body axes. These processes take place in various tissues and organisms, and, hence, raise the question of what common themes and strategies they share. In this article, we review 2 processes that rely on the spatial regulation of periodic and sequential gene activities: segmentation and regionalization of the anterior-posterior (AP) axis of animal body plans. We study these processes in species that belong to 2 different phyla: vertebrates and insects. By contrasting 2 different processes (segmentation and regionalization) in species that belong to 2 distantly related phyla (arthropods and vertebrates), we elucidate the deep logic of patterning by oscillatory and sequential gene activities. Furthermore, in some of these organisms (e.g., the fruit fly Drosophila), a mode of AP patterning has evolved that seems not to overtly rely on oscillations or sequential gene activities, providing an opportunity to study the evolution of pattern formation mechanisms.
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Affiliation(s)
- Margarete Diaz-Cuadros
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
- Department of Pathology, Brigham and Women’s Hospital, Boston, Massachusetts, United States of America
| | - Olivier Pourquié
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
- Department of Pathology, Brigham and Women’s Hospital, Boston, Massachusetts, United States of America
- Harvard Stem Cell Institute, Harvard University, Cambridge, Massachusetts, United States of America
| | - Ezzat El-Sherif
- Division of Developmental Biology, Department of Biology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
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6
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Nakao H. Early embryonic development of Bombyx. Dev Genes Evol 2021; 231:95-107. [PMID: 34296338 DOI: 10.1007/s00427-021-00679-8] [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: 12/03/2020] [Accepted: 07/09/2021] [Indexed: 11/25/2022]
Abstract
Decades have passed since the early molecular embryogenesis of Drosophila melanogaster was outlined. During this period, the molecular mechanisms underlying early embryonic development in other insects, particularly the flour beetle, Tribolium castaneum, have been described in more detail. The information clearly demonstrated that Drosophila embryogenesis is not representative of other insects and has highly distinctive characteristics. At the same time, this new data has been gradually clarifying ancestral operating mechanisms. The silk moth, Bombyx mori, is a lepidopteran insect and, as a representative of the order, has many unique characteristics found in early embryonic development that have not been identified in other insect groups. Herein, some of these characteristics are introduced and discussed in the context of recent information obtained from other insects.
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Affiliation(s)
- Hajime Nakao
- Insect Genome Research and Engineering Unit, Division of Applied Genetics, Institute of Agrobiological Sciences, National Agriculture and Food Research Organization (NARO), 1-2 Oowashi, Tsukuba, Ibaraki, 305-8634, Japan.
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7
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Abstract
Arthropod segmentation and vertebrate somitogenesis are leading fields in the experimental and theoretical interrogation of developmental patterning. However, despite the sophistication of current research, basic conceptual issues remain unresolved. These include: (i) the mechanistic origins of spatial organization within the segment addition zone (SAZ); (ii) the mechanistic origins of segment polarization; (iii) the mechanistic origins of axial variation; and (iv) the evolutionary origins of simultaneous patterning. Here, I explore these problems using coarse-grained models of cross-regulating dynamical processes. In the morphogenetic framework of a row of cells undergoing axial elongation, I simulate interactions between an 'oscillator', a 'switch' and up to three 'timers', successfully reproducing essential patterning behaviours of segmenting systems. By comparing the output of these largely cell-autonomous models to variants that incorporate positional information, I find that scaling relationships, wave patterns and patterning dynamics all depend on whether the SAZ is regulated by temporal or spatial information. I also identify three mechanisms for polarizing oscillator output, all of which functionally implicate the oscillator frequency profile. Finally, I demonstrate significant dynamical and regulatory continuity between sequential and simultaneous modes of segmentation. I discuss these results in the context of the experimental literature.
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Affiliation(s)
- Erik Clark
- Department of Systems Biology, Harvard Medical School, 210 Longwood Ave, Boston, MA 02115, USA
- Trinity College Cambridge, University of Cambridge, Trinity Street, Cambridge CB2 1TQ, UK
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8
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Johnson AB, Lambert JD. The Caudal ParaHox gene is required for hindgut development in the mollusc Tritia (a.k.a. Ilyanassa). Dev Biol 2020; 470:1-9. [PMID: 33191200 DOI: 10.1016/j.ydbio.2020.10.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2019] [Revised: 10/19/2020] [Accepted: 10/20/2020] [Indexed: 11/26/2022]
Abstract
Caudal homeobox genes are found across animals, typically linked to two other homeobox genes in what has been called the ParaHox cluster. These genes have been proposed to pattern the anterior-posterior axis of the endoderm ancestrally, but the expression of Caudal in extant groups is varied and often occurs in other germ layers. Here we examine the role of Caudal in the embryo of the mollusc Tritia (Ilyanassa) obsoleta. ToCaudal expression is initially broad, then becomes progressively restricted and is finally only in the developing hindgut (a.k.a. intestine). Knockdown of ToCaudal using morpholino oligonucleotides specifically blocks hindgut development, indicating that despite its initially broad expression, the functional role of ToCaudal is in hindgut patterning. This is the first functional characterization of Caudal in an animal with spiralian development, which is an ancient mode of embryogenesis that arose early in bilaterian animal evolution. These results are consistent with the hypothesis that the ancestral role of the ParaHox genes was anterior-posterior patterning of the endoderm.
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Affiliation(s)
- Adam B Johnson
- Department of Biology, University of Rochester, Rochester, NY, 14627, USA
| | - J David Lambert
- Department of Biology, University of Rochester, Rochester, NY, 14627, USA.
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9
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Novikova AV, Auman T, Cohen M, Oleynik O, Stahi-Hitin R, Gil E, Weisbrod A, Chipman AD. The multiple roles of caudal in early development of the milkweed bug Oncopeltus fasciatus. Dev Biol 2020; 467:66-76. [PMID: 32891622 DOI: 10.1016/j.ydbio.2020.08.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Revised: 08/25/2020] [Accepted: 08/26/2020] [Indexed: 11/27/2022]
Abstract
The homeobox transcription factor Caudal has conserved roles in all Bilateria in defining the posterior pole and in controlling posterior elongation. These roles are seemingly similar and are difficult to disentangle. We have carried out a detailed analysis of the expression, function and interactions of the caudal ortholog of the milkweed bug, Oncopeltus fasciatus, a hemimetabolous insect with a conservative early development process, in order to understand its different functions throughout development. In Oncopeltus, caudal is not maternally deposited, but has a sequence of roles in the posterior of the embryos throughout early development. It defines and maintains a posterior-anterior gradient in the blastoderm and modulates the activity of segmentation genes in simultaneous segmentation during the blastoderm stage. It later defines the invagination site and the posterior segment addition zone (SAZ) in the germband. It maintains the posterior SAZ cells in an undifferentiated proliferative state, while promoting dynamic expression of segmentation genes in the anterior SAZ. We show that rather than being a simple posterior determinant, Caudal is involved in several distinct regulatory networks, each with a distinct developmental role.
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Affiliation(s)
- Asya V Novikova
- The Department of Ecology, Evolution & Behavior, Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Israel
| | - Tzach Auman
- The Department of Ecology, Evolution & Behavior, Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Israel
| | - Mira Cohen
- The Department of Ecology, Evolution & Behavior, Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Israel
| | - Olesya Oleynik
- The Department of Ecology, Evolution & Behavior, Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Israel
| | - Reut Stahi-Hitin
- The Department of Ecology, Evolution & Behavior, Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Israel
| | - Ella Gil
- The Department of Ecology, Evolution & Behavior, Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Israel
| | - Anat Weisbrod
- The Department of Ecology, Evolution & Behavior, Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Israel
| | - Ariel D Chipman
- The Department of Ecology, Evolution & Behavior, Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Israel.
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10
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Constantinou SJ, Duan N, Nagy LM, Chipman AD, Williams TA. Elongation during segmentation shows axial variability, low mitotic rates, and synchronized cell cycle domains in the crustacean, Thamnocephalus platyurus. EvoDevo 2020; 11:1. [PMID: 31988708 PMCID: PMC6969478 DOI: 10.1186/s13227-020-0147-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2019] [Accepted: 01/03/2020] [Indexed: 12/20/2022] Open
Abstract
Background Segmentation in arthropods typically occurs by sequential addition of segments from a posterior growth zone. However, the amount of tissue required for growth and the cell behaviors producing posterior elongation are sparsely documented. Results Using precisely staged larvae of the crustacean, Thamnocephalus platyurus, we systematically examine cell division patterns and morphometric changes associated with posterior elongation during segmentation. We show that cell division occurs during normal elongation but that cells in the growth zone need only divide ~ 1.5 times to meet growth estimates; correspondingly, direct measures of cell division in the growth zone are low. Morphometric measurements of the growth zone and of newly formed segments suggest tagma-specific features of segment generation. Using methods for detecting two different phases in the cell cycle, we show distinct domains of synchronized cells in the posterior trunk. Borders of cell cycle domains correlate with domains of segmental gene expression, suggesting an intimate link between segment generation and cell cycle regulation. Conclusions Emerging measures of cellular dynamics underlying posterior elongation already show a number of intriguing characteristics that may be widespread among sequentially segmenting arthropods and are likely a source of evolutionary variability. These characteristics include: the low rates of posterior mitosis, the apparently tight regulation of cell cycle at the growth zone/new segment border, and a correlation between changes in elongation and tagma boundaries.
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Affiliation(s)
- Savvas J Constantinou
- 1Biology Department, Trinity College, Hartford, CT USA.,4Present Address: Department of Integrative Biology, Michigan State University, East Lansing, MI 48824 USA
| | - Nicole Duan
- 1Biology Department, Trinity College, Hartford, CT USA.,5Present Address: Bioinformatics and Quantitative Biosciences, Georgia Institute of Technology, North Avenue, Atlanta, GA 30332 USA
| | - Lisa M Nagy
- 2Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ 85721 USA
| | - Ariel D Chipman
- 3The Department of Ecology, Evolution and Behavior, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 91904 Jerusalem, Israel
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11
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An Atlas of Transcription Factors Expressed in Male Pupal Terminalia of Drosophila melanogaster. G3-GENES GENOMES GENETICS 2019; 9:3961-3972. [PMID: 31619460 PMCID: PMC6893207 DOI: 10.1534/g3.119.400788] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
During development, transcription factors and signaling molecules govern gene regulatory networks to direct the formation of unique morphologies. As changes in gene regulatory networks are often implicated in morphological evolution, mapping transcription factor landscapes is important, especially in tissues that undergo rapid evolutionary change. The terminalia (genital and anal structures) of Drosophila melanogaster and its close relatives exhibit dramatic changes in morphology between species. While previous studies have identified network components important for patterning the larval genital disc, the networks governing adult structures during pupal development have remained uncharted. Here, we performed RNA-seq in whole Drosophila melanogaster male terminalia followed by in situ hybridization for 100 highly expressed transcription factors during pupal development. We find that the male terminalia are highly patterned during pupal stages and that specific transcription factors mark separate structures and substructures. Our results are housed online in a searchable database (https://flyterminalia.pitt.edu/) as a resource for the community. This work lays a foundation for future investigations into the gene regulatory networks governing the development and evolution of Drosophila terminalia.
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12
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Quan H, Arsala D, Lynch JA. Transcriptomic and functional analysis of the oosome, a unique form of germ plasm in the wasp Nasonia vitripennis. BMC Biol 2019; 17:78. [PMID: 31601213 PMCID: PMC6785909 DOI: 10.1186/s12915-019-0696-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 08/30/2019] [Indexed: 11/20/2022] Open
Abstract
BACKGROUND The oosome is the germline determinant in the wasp Nasonia vitripennis and is homologous to the polar granules of Drosophila. Despite a common evolutionary origin and developmental role, the oosome is morphologically quite distinct from polar granules. It is a solid sphere that migrates within the cytoplasm before budding out and forming pole cells. RESULTS To gain an understanding of both the molecular basis of oosome development and the conserved essential features of germ plasm, we quantified and compared transcript levels between embryo fragments that contained the oosome and those that did not. The identity of the differentially localized transcripts indicated that Nasonia uses a distinct set of molecules to carry out conserved germ plasm functions. In addition, functional testing of a sample of localized transcripts revealed potentially novel mechanisms of ribonucleoprotein assembly and pole cell cellularization in the wasp. CONCLUSIONS Our results demonstrate that the composition of germ plasm varies significantly within Holometabola, as very few mRNAs share localization to the oosome and polar granules. Some of this variability appears to be related to the unique properties of the oosome relative to the polar granules in Drosophila, and some may be related to differences in pole formation between species. This work will serve as the basis for further investigation into the patterns of germline determinant evolution among insects, the molecular basis of the unique properties of the oosome, and the incorporation of novel components into developmental networks.
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Affiliation(s)
- Honghu Quan
- Department of Pathology and Department of Cell and Molecular Biology, St. Jude Children’s Research Hospital, Memphis, TN 38105 USA
| | - Deanna Arsala
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL 60607 USA
| | - Jeremy A. Lynch
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL 60607 USA
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13
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Rudolf H, Zellner C, El-Sherif E. Speeding up anterior-posterior patterning of insects by differential initialization of the gap gene cascade. Dev Biol 2019; 460:20-31. [PMID: 31075221 DOI: 10.1016/j.ydbio.2019.04.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2018] [Revised: 04/25/2019] [Accepted: 04/25/2019] [Indexed: 01/28/2023]
Abstract
Recently, it was shown that anterior-posterior patterning genes in the red flour beetle Tribolium castaneum are expressed sequentially in waves. However, in the fruit fly Drosophila melanogaster, an insect with a derived mode of embryogenesis compared to Tribolium, anterior-posterior patterning genes quickly and simultaneously arise as mature gene expression domains that, afterwards, undergo slight posterior-to-anterior shifts. This raises the question of how a fast and simultaneous mode of patterning, like that of Drosophila, could have evolved from a rather slow sequential mode of patterning, like that of Tribolium. In this paper, we propose a mechanism for this evolutionary transition based on a switch from a uniform to a gradient-mediated initialization of the gap gene cascade by maternal Hb. The model is supported by computational analyses and experiments.
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Affiliation(s)
- Heike Rudolf
- Department of Biology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Staudtstrasse 5, Erlangen, 91058, Germany
| | - Christine Zellner
- Department of Biology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Staudtstrasse 5, Erlangen, 91058, Germany
| | - Ezzat El-Sherif
- Department of Biology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Staudtstrasse 5, Erlangen, 91058, Germany.
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14
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Shimizu Y, Tamai T, Goto SG. Cell cycle regulator, small silencing RNA, and segmentation patterning gene expression in relation to embryonic diapause in the band-legged ground cricket. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2018; 102:75-83. [PMID: 30287269 DOI: 10.1016/j.ibmb.2018.09.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Revised: 09/03/2018] [Accepted: 09/27/2018] [Indexed: 06/08/2023]
Abstract
Insects enter diapause to synchronize their life cycle with biotic and abiotic conditions favorable for their development, reproduction, and survival. Adult females of the band-legged ground cricket Dianemobius nigrofasciatus (Orthoptera, Glyllidae) respond to environmental factors in autumn and lay diapause-destined eggs. The eggs arrest their development and enter diapause at a very early embryonic stage, specifically the cellular blastoderm. To elucidate the physiological mechanisms underlying this very early stage programmed developmental arrest, we investigated the cell division cycle as well as the expression of cell cycle regulators, small silencing RNAs, and segment patterning genes. The diapause embryo arrests its cell cycle predominantly at the G0/G1 phase. The proportion of cells in the S phase of the cell cycle abruptly decreased at the time of developmental arrest, but further changes of the G0/G1 and G2/M were later observed. Thus, cell cycle arrest in the diapause embryo is not an immediate event, but it takes longer to reach the steady state. We further elucidated molecular events possibly involved in diapause preparation and entry. Downregulation of Proliferating cellular antigen (PCNA; a cell cycle regulator), caudal and pumilio (cad and pum; early segmentation genes) as well as P-element induced wimpy testis (piwi) (a small silencing RNA) prior to the onset of developmental arrest was notable. The downregulation of PCNA, cad and pum continued even after entry into developmental arrest. In contrast to upregulation in non-diapause eggs, Cyclin D (another cell cycle regulator) and hunchback, Krüppel, and runt (gap and pair-rule genes) were downregulated in diapause eggs. These molecular events may contribute to embryonic diapause of D. nigrofasciatus.
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Affiliation(s)
- Yuta Shimizu
- Graduate School of Science, Osaka City University, Osaka, 558-8585, Japan
| | - Takaaki Tamai
- Graduate School of Science, Osaka City University, Osaka, 558-8585, Japan
| | - Shin G Goto
- Graduate School of Science, Osaka City University, Osaka, 558-8585, Japan.
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15
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Precision in a rush: Trade-offs between reproducibility and steepness of the hunchback expression pattern. PLoS Comput Biol 2018; 14:e1006513. [PMID: 30307984 PMCID: PMC6198997 DOI: 10.1371/journal.pcbi.1006513] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Revised: 10/23/2018] [Accepted: 09/14/2018] [Indexed: 11/19/2022] Open
Abstract
Fly development amazes us by the precision and reproducibility of gene expression, especially since the initial expression patterns are established during very short nuclear cycles. Recent live imaging of hunchback promoter dynamics shows a stable steep binary expression pattern established within the three minute interphase of nuclear cycle 11. Considering expression models of different complexity, we explore the trade-off between the ability of a regulatory system to produce a steep boundary and minimize expression variability between different nuclei. We show how a limited readout time imposed by short developmental cycles affects the gene’s ability to read positional information along the embryo’s anterior posterior axis and express reliably. Comparing our theoretical results to real-time monitoring of the hunchback transcription dynamics in live flies, we discuss possible regulatory strategies, suggesting an important role for additional binding sites, gradients or non-equilibrium binding and modified transcription factor search strategies. Despite very limited time, organisms develop in reproducible ways. In the early stages of fly development the information about maternal signals is read out in a few minutes to produce steep and precise gene expression patterns. Motivated by recent live imaging experiments in fly embryos, we explore the consequences of the trade-off between a rushed but reproducible readout and a steep expression pattern on the regulatory modules of gene expression. We show that the current view of one anterior gradient morphogen binding to six binding sites is quantitatively inconsistent with the experimental data given the short readout time, suggesting other regulatory features.
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16
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Vincent BJ, Staller MV, Lopez-Rivera F, Bragdon MDJ, Pym ECG, Biette KM, Wunderlich Z, Harden TT, Estrada J, DePace AH. Hunchback is counter-repressed to regulate even-skipped stripe 2 expression in Drosophila embryos. PLoS Genet 2018; 14:e1007644. [PMID: 30192762 PMCID: PMC6145585 DOI: 10.1371/journal.pgen.1007644] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Revised: 09/19/2018] [Accepted: 08/17/2018] [Indexed: 01/18/2023] Open
Abstract
Hunchback is a bifunctional transcription factor that can activate and repress gene expression in Drosophila development. We investigated the regulatory DNA sequence features that control Hunchback function by perturbing enhancers for one of its target genes, even-skipped (eve). While Hunchback directly represses the eve stripe 3+7 enhancer, we found that in the eve stripe 2+7 enhancer, Hunchback repression is prevented by nearby sequences-this phenomenon is called counter-repression. We also found evidence that Caudal binding sites are responsible for counter-repression, and that this interaction may be a conserved feature of eve stripe 2 enhancers. Our results alter the textbook view of eve stripe 2 regulation wherein Hb is described as a direct activator. Instead, to generate stripe 2, Hunchback repression must be counteracted. We discuss how counter-repression may influence eve stripe 2 regulation and evolution.
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Affiliation(s)
- Ben J. Vincent
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Max V. Staller
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Francheska Lopez-Rivera
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Meghan D. J. Bragdon
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Edward C. G. Pym
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Kelly M. Biette
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Zeba Wunderlich
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Timothy T. Harden
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Javier Estrada
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Angela H. DePace
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
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17
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Suter B. RNA localization and transport. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2018; 1861:938-951. [PMID: 30496039 DOI: 10.1016/j.bbagrm.2018.08.004] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2018] [Revised: 08/23/2018] [Accepted: 08/23/2018] [Indexed: 12/30/2022]
Abstract
RNA localization serves numerous purposes from controlling development and differentiation to supporting the physiological activities of cells and organisms. After a brief introduction into the history of the study of mRNA localization I will focus on animal systems, describing in which cellular compartments and in which cell types mRNA localization was observed and studied. In recent years numerous novel localization patterns have been described, and countless mRNAs have been documented to accumulate in specific subcellular compartments. These fascinating revelations prompted speculations about the purpose of localizing all these mRNAs. In recent years experimental evidence for an unexpected variety of different functions has started to emerge. Aside from focusing on the functional aspects, I will discuss various ways of localizing mRNAs with a focus on the mechanism of active and directed transport on cytoskeletal tracks. Structural studies combined with imaging of transport and biochemical studies have contributed to the enormous recent progress, particularly in understanding how dynein/dynactin/BicD (DDB) dependent transport on microtubules works. This transport process actively localizes diverse cargo in similar ways to the minus end of microtubules and, at least in flies, also individual mRNA molecules. A sophisticated mechanism ensures that cargo loading licenses processive transport.
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Affiliation(s)
- Beat Suter
- Institute of Cell Biology, University of Bern, 3012 Bern, Switzerland.
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18
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Clark E, Peel AD. Evidence for the temporal regulation of insect segmentation by a conserved sequence of transcription factors. Development 2018; 145:dev.155580. [PMID: 29724758 PMCID: PMC6001374 DOI: 10.1242/dev.155580] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Accepted: 04/25/2018] [Indexed: 01/20/2023]
Abstract
Long-germ insects, such as the fruit fly Drosophila melanogaster, pattern their segments simultaneously, whereas short-germ insects, such as the beetle Tribolium castaneum, pattern their segments sequentially, from anterior to posterior. While the two modes of segmentation at first appear quite distinct, much of this difference might simply reflect developmental heterochrony. We now show here that, in both Drosophila and Tribolium, segment patterning occurs within a common framework of sequential Caudal, Dichaete, and Odd-paired expression. In Drosophila these transcription factors are expressed like simple timers within the blastoderm, while in Tribolium they form wavefronts that sweep from anterior to posterior across the germband. In Drosophila, all three are known to regulate pair-rule gene expression and influence the temporal progression of segmentation. We propose that these regulatory roles are conserved in short-germ embryos, and that therefore the changing expression profiles of these genes across insects provide a mechanistic explanation for observed differences in the timing of segmentation. In support of this hypothesis we demonstrate that Odd-paired is essential for segmentation in Tribolium, contrary to previous reports.
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Affiliation(s)
- Erik Clark
- Laboratory for Development and Evolution, Department of Zoology, University of Cambridge, UK
| | - Andrew D Peel
- Faculty of Biological Sciences, University of Leeds, UK
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19
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A damped oscillator imposes temporal order on posterior gap gene expression in Drosophila. PLoS Biol 2018; 16:e2003174. [PMID: 29451884 PMCID: PMC5832388 DOI: 10.1371/journal.pbio.2003174] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Revised: 03/01/2018] [Accepted: 01/31/2018] [Indexed: 12/21/2022] Open
Abstract
Insects determine their body segments in two different ways. Short-germband insects, such as the flour beetle Tribolium castaneum, use a molecular clock to establish segments sequentially. In contrast, long-germband insects, such as the vinegar fly Drosophila melanogaster, determine all segments simultaneously through a hierarchical cascade of gene regulation. Gap genes constitute the first layer of the Drosophila segmentation gene hierarchy, downstream of maternal gradients such as that of Caudal (Cad). We use data-driven mathematical modelling and phase space analysis to show that shifting gap domains in the posterior half of the Drosophila embryo are an emergent property of a robust damped oscillator mechanism, suggesting that the regulatory dynamics underlying long- and short-germband segmentation are much more similar than previously thought. In Tribolium, Cad has been proposed to modulate the frequency of the segmentation oscillator. Surprisingly, our simulations and experiments show that the shift rate of posterior gap domains is independent of maternal Cad levels in Drosophila. Our results suggest a novel evolutionary scenario for the short- to long-germband transition and help explain why this transition occurred convergently multiple times during the radiation of the holometabolan insects. Different insect species exhibit one of two distinct modes of determining their body segments (known as segmentation) during development: they either use a molecular oscillator to position segments sequentially, or they generate segments simultaneously through a hierarchical gene-regulatory cascade. The sequential mode is ancestral, while the simultaneous mode has been derived from it independently several times during evolution. In this paper, we present evidence suggesting that simultaneous segmentation also involves an oscillator in the posterior end of the embryo of the vinegar fly, Drosophila melanogaster. This surprising result indicates that both modes of segment determination are much more similar than previously thought. Such similarity provides an important step towards our understanding of the frequent evolutionary transitions observed between sequential and simultaneous segmentation.
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20
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Speed regulation of genetic cascades allows for evolvability in the body plan specification of insects. Proc Natl Acad Sci U S A 2017; 114:E8646-E8655. [PMID: 28973882 DOI: 10.1073/pnas.1702478114] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
During the anterior-posterior fate specification of insects, anterior fates arise in a nonelongating tissue (called the "blastoderm"), and posterior fates arise in an elongating tissue (called the "germband"). However, insects differ widely in the extent to which anterior-posterior fates are specified in the blastoderm versus the germband. Here we present a model in which patterning in both the blastoderm and germband of the beetle Tribolium castaneum is based on the same flexible mechanism: a gradient that modulates the speed of a genetic cascade of gap genes, resulting in the induction of sequential kinematic waves of gap gene expression. The mechanism is flexible and capable of patterning both elongating and nonelongating tissues, and hence converting blastodermal to germband fates and vice versa. Using RNAi perturbations, we found that blastodermal fates could be shifted to the germband, and germband fates could be generated in a blastoderm-like morphology. We also suggest a molecular mechanism underlying our model, in which gradient levels regulate the switch between two enhancers: One enhancer is responsible for sequential gene activation, and the other is responsible for freezing temporal rhythms into spatial patterns. This model is consistent with findings in Drosophila melanogaster, where gap genes were found to be regulated by two nonredundant "shadow" enhancers.
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21
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Williams TA, Nagy LM. Linking gene regulation to cell behaviors in the posterior growth zone of sequentially segmenting arthropods. ARTHROPOD STRUCTURE & DEVELOPMENT 2017; 46:380-394. [PMID: 27720841 DOI: 10.1016/j.asd.2016.10.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2016] [Accepted: 10/03/2016] [Indexed: 06/06/2023]
Abstract
Virtually all arthropods all arthropods add their body segments sequentially, one by one in an anterior to posterior progression. That process requires not only segment specification but typically growth and elongation. Here we review the functions of some of the key genes that regulate segmentation: Wnt, caudal, Notch pathway, and pair-rule genes, and discuss what can be inferred about their evolution. We focus on how these regulatory factors are integrated with growth and elongation and discuss the importance and challenges of baseline measures of growth and elongation. We emphasize a perspective that integrates the genetic regulation of segment patterning with the cellular mechanisms of growth and elongation.
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Affiliation(s)
| | - Lisa M Nagy
- Department of Molecular and Cellular Biology, The University of Arizona, Tucson, AZ 85721, USA.
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22
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Auman T, Vreede BMI, Weiss A, Hester SD, Williams TA, Nagy LM, Chipman AD. Dynamics of growth zone patterning in the milkweed bug Oncopeltus fasciatus. Development 2017; 144:1896-1905. [PMID: 28432218 PMCID: PMC5450833 DOI: 10.1242/dev.142091] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Accepted: 04/10/2017] [Indexed: 01/19/2023]
Abstract
We describe the dynamic process of abdominal segment generation in the milkweed bug Oncopeltus fasciatus. We present detailed morphological measurements of the growing germband throughout segmentation. Our data are complemented by cell division profiles and expression patterns of key genes, including invected and even-skipped as markers for different stages of segment formation. We describe morphological and mechanistic changes in the growth zone and in nascent segments during the generation of individual segments and throughout segmentation, and examine the relative contribution of newly formed versus existing tissue to segment formation. Although abdominal segment addition is primarily generated through the rearrangement of a pool of undifferentiated cells, there is nonetheless proliferation in the posterior. By correlating proliferation with gene expression in the growth zone, we propose a model for growth zone dynamics during segmentation in which the growth zone is functionally subdivided into two distinct regions: a posterior region devoted to a slow rate of growth among undifferentiated cells, and an anterior region in which segmental differentiation is initiated and proliferation inhibited. Summary: A detailed analysis of posterior segment addition in an insect reveals that the growth zone is divided into two functional domains responsible for growth and differentiation.
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Affiliation(s)
- Tzach Auman
- Department of Ecology, Evolution and Behavior, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram 91904, Jerusalem, Israel
| | - Barbara M I Vreede
- Department of Ecology, Evolution and Behavior, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram 91904, Jerusalem, Israel
| | - Aryeh Weiss
- Faculty of Engineering and The Bar-Ilan Institute of Nanotechnology & Advanced Materials, Bar Ilan University, Ramat Gan 52900, Israel.,Bio-Imaging Unit, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram 91904, Jerusalem, Israel
| | - Susan D Hester
- Molecular and Cellular Biology Department, University of Arizona, Tucson, AZ 85721, USA
| | | | - Lisa M Nagy
- Molecular and Cellular Biology Department, University of Arizona, Tucson, AZ 85721, USA
| | - Ariel D Chipman
- Department of Ecology, Evolution and Behavior, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram 91904, Jerusalem, Israel
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23
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Schmidt-Ott U, Lynch JA. Emerging developmental genetic model systems in holometabolous insects. Curr Opin Genet Dev 2016; 39:116-128. [PMID: 27399647 DOI: 10.1016/j.gde.2016.06.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Revised: 05/25/2016] [Accepted: 06/08/2016] [Indexed: 01/08/2023]
Abstract
The number of insect species that are amenable to functional genetic studies is growing rapidly and provides many new research opportunities in developmental and evolutionary biology. The holometabolous insects represent a disproportionate percentage of animal diversity and are thus well positioned to provide model species for a wide variety of developmental processes. Here we discuss emerging holometabolous models, and review some recent breakthroughs. For example, flies and midges were found to use structurally unrelated long-range pattern organizers, butterflies and moths revealed extensive pattern formation during oogenesis, new imaging possibilities in the flour beetle Tribolium castaneum showed how embryos break free of their extraembryonic membranes, and the complex genetics governing interspecies difference in head shape were revealed in Nasonia wasps.
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Affiliation(s)
- Urs Schmidt-Ott
- Department of Organismal Biology and Anatomy, University of Chicago, United States.
| | - Jeremy A Lynch
- Department of Biological Sciences, University of Illinois at Chicago, United States.
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24
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Rothschild JB, Tsimiklis P, Siggia ED, François P. Predicting Ancestral Segmentation Phenotypes from Drosophila to Anopheles Using In Silico Evolution. PLoS Genet 2016; 12:e1006052. [PMID: 27227405 PMCID: PMC4882032 DOI: 10.1371/journal.pgen.1006052] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Accepted: 04/23/2016] [Indexed: 12/23/2022] Open
Abstract
Molecular evolution is an established technique for inferring gene homology but regulatory DNA turns over so rapidly that inference of ancestral networks is often impossible. In silico evolution is used to compute the most parsimonious path in regulatory space for anterior-posterior patterning linking two Dipterian species. The expression pattern of gap genes has evolved between Drosophila (fly) and Anopheles (mosquito), yet one of their targets, eve, has remained invariant. Our model predicts that stripe 5 in fly disappears and a new posterior stripe is created in mosquito, thus eve stripe modules 3+7 and 4+6 in fly are homologous to 3+6 and 4+5 in mosquito. We can place Clogmia on this evolutionary pathway and it shares the mosquito homologies. To account for the evolution of the other pair-rule genes in the posterior we have to assume that the ancestral Dipterian utilized a dynamic method to phase those genes in relation to eve. The last common ancestor of the fruit fly (Drosophila) and mosquito (Anopheles) lived more than 200 Million years ago. Can we use available data on insects alive today to infer what their ancestor looked like? In this manuscript, we focus on early embryonic development, when stripes of genetic expression appear and define the location of insect segments (“segmentation”). We use an evolutionary algorithm to reconstruct and predict dynamics of genes controlling stripes in the last common ancestor of fly and mosquito. We predict a new and different combinatorial logic of stripe formation in mosquito compared to fly, which is fully consistent with development of intermediate species such as moth-fly (Clogmia). Our simulations further suggest that the dynamics of gene expression in this last common ancestor were similar to other insects, such as wasps (Nasonia). Our method illustrates how computational methods inspired by machine learning and non-linear physics can be used to infer gene dynamics in species that disappeared millions of years ago.
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Affiliation(s)
- Jeremy B. Rothschild
- Physics Department, McGill University, Ernest Rutherford Physics Building, Montreal, Quebec, Canada
| | - Panagiotis Tsimiklis
- Physics Department, McGill University, Ernest Rutherford Physics Building, Montreal, Quebec, Canada
| | - Eric D. Siggia
- Center for Studies in Physics and Biology, The Rockefeller University, New York, New York, United States of America
| | - Paul François
- Physics Department, McGill University, Ernest Rutherford Physics Building, Montreal, Quebec, Canada
- * E-mail:
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25
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Janssen R, Budd GE. Gene expression analysis reveals that Delta/Notch signalling is not involved in onychophoran segmentation. Dev Genes Evol 2016; 226:69-77. [PMID: 26935716 PMCID: PMC4819559 DOI: 10.1007/s00427-016-0529-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2015] [Accepted: 02/09/2016] [Indexed: 11/24/2022]
Abstract
Delta/Notch (Dl/N) signalling is involved in the gene regulatory network underlying the segmentation process in vertebrates and possibly also in annelids and arthropods, leading to the hypothesis that segmentation may have evolved in the last common ancestor of bilaterian animals. Because of seemingly contradicting results within the well-studied arthropods, however, the role and origin of Dl/N signalling in segmentation generally is still unclear. In this study, we investigate core components of Dl/N signalling by means of gene expression analysis in the onychophoran Euperipatoides kanangrensis, a close relative to the arthropods. We find that neither Delta or Notch nor any other investigated components of its signalling pathway are likely to be involved in segment addition in onychophorans. We instead suggest that Dl/N signalling may be involved in posterior elongation, another conserved function of these genes. We suggest further that the posterior elongation network, rather than classic Dl/N signalling, may be in the control of the highly conserved segment polarity gene network and the lower-level pair-rule gene network in onychophorans. Consequently, we believe that the pair-rule gene network and its interaction with Dl/N signalling may have evolved within the arthropod lineage and that Dl/N signalling has thus likely been recruited independently for segment addition in different phyla.
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Affiliation(s)
- Ralf Janssen
- Department of Earth Sciences, Palaeobiology, Uppsala University, Villavägen 16, 75236, Uppsala, Sweden.
| | - Graham E Budd
- Department of Earth Sciences, Palaeobiology, Uppsala University, Villavägen 16, 75236, Uppsala, Sweden
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26
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Hoermann A, Cicin-Sain D, Jaeger J. A quantitative validated model reveals two phases of transcriptional regulation for the gap gene giant in Drosophila. Dev Biol 2016; 411:325-338. [DOI: 10.1016/j.ydbio.2016.01.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2015] [Revised: 12/22/2015] [Accepted: 01/08/2016] [Indexed: 01/05/2023]
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27
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Carter JM, Gibbs M, Breuker CJ. Divergent RNA Localisation Patterns of Maternal Genes Regulating Embryonic Patterning in the Butterfly Pararge aegeria. PLoS One 2015; 10:e0144471. [PMID: 26633019 PMCID: PMC4669120 DOI: 10.1371/journal.pone.0144471] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Accepted: 11/18/2015] [Indexed: 12/19/2022] Open
Abstract
The maternal effect genes responsible for patterning the embryo along the antero-posterior (AP) axis are broadly conserved in insects. The precise function of these maternal effect genes is the result of the localisation of their mRNA in the oocyte. The main developmental mechanisms involved have been elucidated in Drosophila melanogaster, but recent studies have shown that other insect orders often diverge in RNA localisation patterns. A recent study has shown that in the butterfly Pararge aegeria the distinction between blastodermal embryonic (i.e. germ band) and extra-embryonic tissue (i.e. serosa) is already specified in the oocyte during oogenesis in the ovariole, long before blastoderm cellularisation. To examine the extent by which a female butterfly specifies and patterns the AP axis within the region fated to be the germ band, and whether she specifies a germ plasm, we performed in situ hybridisation experiments on oocytes in P. aegeria ovarioles and on early embryos. RNA localisation of the following key maternal effect genes were investigated: caudal (cad), orthodenticle (otd), hunchback (hb) and four nanos (nos) paralogs, as well as TDRD7 a gene containing a key functional domain (OST-HTH/LOTUS) shared with oskar. TDRD7 was mainly confined to the follicle cells, whilst hb was exclusively zygotically transcribed. RNA of some of the nos paralogs, otd and cad revealed complex localisation patterns within the cortical region prefiguring the germ band (i.e. germ cortex). Rather interestingly, otd was localised within and outside the anterior of the germ cortex. Transcripts of nos-O formed a distinct granular ring in the middle of the germ cortex possibly prefiguring the region where germline stem cells form. These butterfly RNA localisation patterns are highly divergent with respect to other insects, highlighting the diverse ways in which different insect orders maternally regulate early embryogenesis of their offspring.
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Affiliation(s)
- Jean-Michel Carter
- Evolutionary Developmental Biology Research Group, Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes University, Gipsy Lane, Headington, Oxford, OX3 0BP, United Kingdom
| | - Melanie Gibbs
- NERC Centre for Ecology & Hydrology, Maclean Building, Benson Lane, Crowmarsh Gifford, Wallingford, Oxfordshire, OX10 8BB, United Kingdom
| | - Casper J. Breuker
- Evolutionary Developmental Biology Research Group, Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes University, Gipsy Lane, Headington, Oxford, OX3 0BP, United Kingdom
- * E-mail:
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28
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Kazemian M, Suryamohan K, Chen JY, Zhang Y, Samee MAH, Halfon MS, Sinha S. Evidence for deep regulatory similarities in early developmental programs across highly diverged insects. Genome Biol Evol 2015; 6:2301-20. [PMID: 25173756 PMCID: PMC4217690 DOI: 10.1093/gbe/evu184] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Many genes familiar from Drosophila development, such as the so-called gap, pair-rule, and segment polarity genes, play important roles in the development of other insects and in many cases appear to be deployed in a similar fashion, despite the fact that Drosophila-like "long germband" development is highly derived and confined to a subset of insect families. Whether or not these similarities extend to the regulatory level is unknown. Identification of regulatory regions beyond the well-studied Drosophila has been challenging as even within the Diptera (flies, including mosquitoes) regulatory sequences have diverged past the point of recognition by standard alignment methods. Here, we demonstrate that methods we previously developed for computational cis-regulatory module (CRM) discovery in Drosophila can be used effectively in highly diverged (250-350 Myr) insect species including Anopheles gambiae, Tribolium castaneum, Apis mellifera, and Nasonia vitripennis. In Drosophila, we have successfully used small sets of known CRMs as "training data" to guide the search for other CRMs with related function. We show here that although species-specific CRM training data do not exist, training sets from Drosophila can facilitate CRM discovery in diverged insects. We validate in vivo over a dozen new CRMs, roughly doubling the number of known CRMs in the four non-Drosophila species. Given the growing wealth of Drosophila CRM annotation, these results suggest that extensive regulatory sequence annotation will be possible in newly sequenced insects without recourse to costly and labor-intensive genome-scale experiments. We develop a new method, Regulus, which computes a probabilistic score of similarity based on binding site composition (despite the absence of nucleotide-level sequence alignment), and demonstrate similarity between functionally related CRMs from orthologous loci. Our work represents an important step toward being able to trace the evolutionary history of gene regulatory networks and defining the mechanisms underlying insect evolution.
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Affiliation(s)
- Majid Kazemian
- Department of Computer Science, University of Illinois at Urbana-Champaign Laboratory of Molecular Immunology, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland
| | - Kushal Suryamohan
- Department of Biochemistry, University at Buffalo-State University of New York NY State Center of Excellence in Bioinformatics and Life Sciences, Buffalo, New York
| | - Jia-Yu Chen
- Department of Computer Science, University of Illinois at Urbana-Champaign
| | - Yinan Zhang
- Department of Computer Science, University of Illinois at Urbana-Champaign
| | | | - Marc S Halfon
- Department of Biochemistry, University at Buffalo-State University of New York NY State Center of Excellence in Bioinformatics and Life Sciences, Buffalo, New York Department of Biological Sciences, University at Buffalo-State University of New York Molecular and Cellular Biology Department and Program in Cancer Genetics, Roswell Park Cancer Institute, Buffalo, New York
| | - Saurabh Sinha
- Department of Computer Science, University of Illinois at Urbana-Champaign Institute of Genomic Biology, University of Illinois at Urbana-Champaign
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29
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Wotton KR, Jiménez-Guri E, Jaeger J. Maternal co-ordinate gene regulation and axis polarity in the scuttle fly Megaselia abdita. PLoS Genet 2015; 11:e1005042. [PMID: 25757102 PMCID: PMC4355411 DOI: 10.1371/journal.pgen.1005042] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2014] [Accepted: 01/30/2015] [Indexed: 02/01/2023] Open
Abstract
Axis specification and segment determination in dipteran insects are an excellent model system for comparative analyses of gene network evolution. Antero-posterior polarity of the embryo is established through systems of maternal morphogen gradients. In Drosophila melanogaster, the anterior system acts through opposing gradients of Bicoid (Bcd) and Caudal (Cad), while the posterior system involves Nanos (Nos) and Hunchback (Hb) protein. These systems act redundantly. Both Bcd and Hb need to be eliminated to cause a complete loss of polarity resulting in mirror-duplicated abdomens, so-called bicaudal phenotypes. In contrast, knock-down of bcd alone is sufficient to induce double abdomens in non-drosophilid cyclorrhaphan dipterans such as the hoverfly Episyrphus balteatus or the scuttle fly Megaselia abdita. We investigate conserved and divergent aspects of axis specification in the cyclorrhaphan lineage through a detailed study of the establishment and regulatory effect of maternal gradients in M. abdita. Our results show that the function of the anterior maternal system is highly conserved in this species, despite the loss of maternal cad expression. In contrast, hb does not activate gap genes in this species. The absence of this activatory role provides a precise genetic explanation for the loss of polarity upon bcd knock-down in M. abdita, and suggests a general scenario in which the posterior maternal system is increasingly replaced by the anterior one during the evolution of the cyclorrhaphan dipteran lineage. The basic head-to-tail polarity of an animal is established very early in development. In dipteran insects (flies, midges, and mosquitoes), polarity is established with the help of so-called morphogen gradients. Morphogens are regulatory proteins that are distributed as a concentration gradient, often involving diffusion from a localised source. This graded distribution then leads to the concentration-dependent activation of different target genes along the embryo’s axis. We examine this process, which differs to a surprising extent between dipteran species, in the scuttle fly Megaselia abdita, and compare our results to the model organism Drosophila melanogaster. In this way, we not only gain insights into how the mechanisms that establish polarity function differently in different species, but also how the system has evolved since these two flies shared a common ancestor. Specifically, we pin down the main difference between Drosophila and Megaselia in the altered function of the maternal Hunchback morphogen gradient, which activates target genes in the former, but not the latter species, where it has been completely replaced by the Bicoid morphogen during evolution.
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Affiliation(s)
- Karl R. Wotton
- EMBL/CRG Research Unit in Systems Biology, Centre for Genomic Regulation (CRG), Barcelona, Spain
- Universitat Pompeu Fabra (UPF), Barcelona, Spain
- * E-mail: (KW); (JJ)
| | - Eva Jiménez-Guri
- EMBL/CRG Research Unit in Systems Biology, Centre for Genomic Regulation (CRG), Barcelona, Spain
- Universitat Pompeu Fabra (UPF), Barcelona, Spain
| | - Johannes Jaeger
- EMBL/CRG Research Unit in Systems Biology, Centre for Genomic Regulation (CRG), Barcelona, Spain
- Universitat Pompeu Fabra (UPF), Barcelona, Spain
- * E-mail: (KW); (JJ)
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Caudal regulates the spatiotemporal dynamics of pair-rule waves in Tribolium. PLoS Genet 2014; 10:e1004677. [PMID: 25329152 PMCID: PMC4199486 DOI: 10.1371/journal.pgen.1004677] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Accepted: 08/18/2014] [Indexed: 12/22/2022] Open
Abstract
In the short-germ beetle Tribolium castaneum, waves of pair-rule gene expression propagate from the posterior end of the embryo towards the anterior and eventually freeze into stable stripes, partitioning the anterior-posterior axis into segments. Similar waves in vertebrates are assumed to arise due to the modulation of a molecular clock by a posterior-to-anterior frequency gradient. However, neither a molecular candidate nor a functional role has been identified to date for such a frequency gradient, either in vertebrates or elsewhere. Here we provide evidence that the posterior gradient of Tc-caudal expression regulates the oscillation frequency of pair-rule gene expression in Tribolium. We show this by analyzing the spatiotemporal dynamics of Tc-even-skipped expression in strong and mild knockdown of Tc-caudal, and by correlating the extension, level and slope of the Tc-caudal expression gradient to the spatiotemporal dynamics of Tc-even-skipped expression in wild type as well as in different RNAi knockdowns of Tc-caudal regulators. Further, we show that besides its absolute importance for stripe generation in the static phase of the Tribolium blastoderm, a frequency gradient might serve as a buffer against noise during axis elongation phase in Tribolium as well as vertebrates. Our results highlight the role of frequency gradients in pattern formation. One of the most popular problems in development is how the anterior-posterior axis of vertebrates, arthropods and annelids is partitioned into segments. In vertebrates, and recently shown in the beetle Tribolium castaneum, segments are demarcated by means of gene expression waves that propagate from posterior to anterior as the embryo elongates. These waves are assumed to arise due to the regulation of a molecular clock by a frequency gradient. However, to date, neither a candidate nor a functional role has been identified for such a frequency gradient. Here we provide evidence that a static expression gradient of caudal regulates pair-rule oscillations during blastoderm stage in Tribolium. In such a static setup, a frequency gradient is essential to convert clock oscillations into a striped pattern. We further show that a frequency gradient might be essential even in the presence of axis elongation as a buffer against noise. Our work also provides the best evidence to date that Caudal acts as a type of morphogen gradient in the blastoderm of short-germ arthropods; however, Caudal seems to convey positional information through frequency regulation of pair-rule oscillations, rather than through threshold concentration levels in the gradient.
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Lynch JA. Diversity of molecules and mechanisms in establishing insect anterior-posterior polarity. CURRENT OPINION IN INSECT SCIENCE 2014; 1:39-44. [PMID: 32846728 DOI: 10.1016/j.cois.2014.05.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2014] [Revised: 04/27/2014] [Accepted: 05/02/2014] [Indexed: 06/11/2023]
Abstract
Anterior-posterior (AP) patterning is an essential process that requires the generation of large amounts of positional information to properly specify many distinct cell fates along the long axis of the insect embryo. While the general molecular basis of this process has long been known in the fly Drosophila, detailed understanding of this process is still emerging in other insect species. What is now clear is that this process in extremely labile, and distinct AP patterning programs can exist even within a single species. This review presents recent progress on this topic in an attempt to synthesize the disparate data and provide an outlook on the future of the field.
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Affiliation(s)
- Jeremy A Lynch
- University of Illinois at Chicago, 4020 MBRB, 900 Ashland Ave., Chicago, IL 60607, USA.
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Wilson MJ, Kenny NJ, Dearden PK. Components of the dorsal-ventral pathway also contribute to anterior-posterior patterning in honeybee embryos (Apis mellifera). EvoDevo 2014; 5:11. [PMID: 24620747 PMCID: PMC3995682 DOI: 10.1186/2041-9139-5-11] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Accepted: 01/20/2014] [Indexed: 01/27/2023] Open
Abstract
Background A key early step in embryogenesis is the establishment of the major body axes; the dorsal-ventral (DV) and anterior-posterior (AP) axes. Determination of these axes in some insects requires the function of different sets of signalling pathways for each axis. Patterning across the DV axis requires interaction between the Toll and Dpp/TGF-β pathways, whereas patterning across the AP axis requires gradients of bicoid/orthodenticle proteins and the actions of a hierarchy of gene transcription factors. We examined the expression and function of Toll and Dpp signalling during honeybee embryogenesis to assess to the role of these genes in DV patterning. Results Pathway components that are required for dorsal specification in Drosophila are expressed in an AP-restricted pattern in the honeybee embryo, including Dpp and its receptor Tkv. Components of the Toll pathway are expressed in a more conserved pattern along the ventral axis of the embryo. Late-stage embryos from RNA interference (RNAi) knockdown of Toll and Dpp pathways had both DV and AP patterning defects, confirmed by staining with Am-sna, Am-zen, Am-eve, and Am-twi at earlier stages. We also identified two orthologues of dorsal in the honeybee genome, with one being expressed during embryogenesis and having a minor role in axis patterning, as determined by RNAi and the other expressed during oogenesis. Conclusions We found that early acting pathways (Toll and Dpp) are involved not only in DV patterning but also AP patterning in honeybee embryogenesis. Changes to the expression patterns and function of these genes may reflect evolutionary changes in the placement of the extra-embryonic membranes during embryogenesis with respect to the AP and DV axes.
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Affiliation(s)
- Megan J Wilson
- Developmental Biology Laboratory, Department of Anatomy, University of Otago, P,O, Box 56, Dunedin 9054, New Zealand.
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Rosenberg MI, Brent AE, Payre F, Desplan C. Dual mode of embryonic development is highlighted by expression and function of Nasonia pair-rule genes. eLife 2014; 3:e01440. [PMID: 24599282 PMCID: PMC3941026 DOI: 10.7554/elife.01440] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Embryonic anterior-posterior patterning is well understood in Drosophila, which uses 'long germ' embryogenesis, in which all segments are patterned before cellularization. In contrast, most insects use 'short germ' embryogenesis, wherein only head and thorax are patterned in a syncytial environment while the remainder of the embryo is generated after cellularization. We use the wasp Nasonia (Nv) to address how the transition from short to long germ embryogenesis occurred. Maternal and gap gene expression in Nasonia suggest long germ embryogenesis. However, the Nasonia pair-rule genes even-skipped, odd-skipped, runt and hairy are all expressed as early blastoderm pair-rule stripes and late-forming posterior stripes. Knockdown of Nv eve, odd or h causes loss of alternate segments at the anterior and complete loss of abdominal segments. We propose that Nasonia uses a mixed mode of segmentation wherein pair-rule genes pattern the embryo in a manner resembling Drosophila at the anterior and ancestral Tribolium at the posterior. DOI: http://dx.doi.org/10.7554/eLife.01440.001.
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Affiliation(s)
- Miriam I Rosenberg
- Center for Developmental Genetics, Department of Biology, New York University, New York, United States
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Chang CC, Hsiao YM, Huang TY, Cook CE, Shigenobu S, Chang TH. Noncanonical expression of caudal during early embryogenesis in the pea aphid Acyrthosiphon pisum: maternal cad-driven posterior development is not conserved. INSECT MOLECULAR BIOLOGY 2013; 22:442-455. [PMID: 23683148 DOI: 10.1111/imb.12035] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Previously we identified anterior localization of hunchback (Aphb) mRNA in oocytes and early embryos of the parthenogenetic and viviparous pea aphid Acyrthosiphon pisum, suggesting that the breaking of anterior asymmetry in the oocytes leads to the formation of the anterior axis in embryos. In order to study posterior development in the asexual pea aphid, we cloned and analysed the developmental expression of caudal (Apcad), a posterior gene highly conserved in many animal phyla. We found that transcripts of Apcad were not detected in germaria, oocytes and embryos prior to the formation of the blastoderm in the asexual (viviparous) pea aphid. This unusual expression pattern differs from that of the existing insect models, including long- and short-germ insects, where maternal cad mRNA is passed to the early embryos and forms a posterior-anterior gradient. The first detectable Apcad expression occurred in the newly formed primordial germ cells and their adjacent blastodermal cells during late blastulation. From gastrulation onward, and as in other insects, Apcad mRNA is restricted to the posteriormost region of the germ band. Similarly, in the sexual (oviparous) oocytes we were able to identify anterior localization of Aphb mRNA but posterior localization of Apcad was not detected. This suggests that cad-driven posterior development is not conserved during early embryogenesis in asexual and sexual pea aphids.
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Affiliation(s)
- C-C Chang
- Laboratory for Genetics and Development, Department of Entomology/Institute of Biotechnology, College of Bio-Resources and Agriculture, National Taiwan University, Taipei, Taiwan.
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35
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Verhulst EC, Lynch JA, Bopp D, Beukeboom LW, van de Zande L. A new component of the Nasonia sex determining cascade is maternally silenced and regulates transformer expression. PLoS One 2013; 8:e63618. [PMID: 23717455 PMCID: PMC3661551 DOI: 10.1371/journal.pone.0063618] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Accepted: 04/04/2013] [Indexed: 01/28/2023] Open
Abstract
Although sex determination is a universal process in sexually reproducing organisms, sex determination pathways are among the most highly variable genetic systems found in nature. Nevertheless, general principles can be identified among the diversity, like the central role of transformer (tra) in insects. When a functional TRA protein is produced in early embryogenesis, the female sex determining route is activated, while prevention of TRA production leads to male development. In dipterans, male development is achieved by prevention of female-specific splicing of tra mRNA, either mediated by X-chromosome dose or masculinizing factors. In Hymenoptera, which have haplodiploid sex determination, complementary sex determination and maternal imprinting have been identified to regulate timely TRA production. In the parasitoid Nasonia, zygotic transformer (Nvtra) expression and splicing is regulated by a combination of maternal provision of Nvtra mRNA and silencing of Nvtra expression in unfertilized eggs. It is unclear, however, if this silencing is directly on the tra locus or whether it is mediated through maternal silencing of a trans-acting factor. Here we show that in Nasonia, female sex determination is dependent on zygotic activation of Nvtra expression by an as yet unknown factor. This factor, which we propose to term womanizer (wom), is maternally silenced during oogenesis to ensure male development in unfertilized eggs. This finding implicates the upstream recruitment of a novel gene in the Nasonia sex determining cascade and supports the notion that sex determining cascades can rapidly change by adding new components on top of existing regulators.
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Affiliation(s)
- Eveline C Verhulst
- University of Groningen, Center for Ecological and Evolutionary Studies, Evolutionary Genetics, Groningen, The Netherlands.
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36
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Duncan EJ, Leask MP, Dearden PK. The pea aphid (Acyrthosiphon pisum) genome encodes two divergent early developmental programs. Dev Biol 2013; 377:262-74. [PMID: 23416037 DOI: 10.1016/j.ydbio.2013.01.036] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Revised: 01/18/2013] [Accepted: 01/29/2013] [Indexed: 12/28/2022]
Abstract
The pea aphid (Acyrthosiphon pisum) can reproduce either sexually or asexually (parthenogenetically), giving rise, in each case, to almost identical adults. These two modes of reproduction are accompanied by differences in ovarian morphology and the developmental environment of the offspring, with sexual forms producing eggs that are laid, whereas asexual development occurs within the mother. Here we examine the effect each mode of reproduction has on the expression of key maternal and axis patterning genes; orthodenticle (otd), hunchback (hb), caudal (cad) and nanos (nos). We show that three of these genes (Ap-hb, Ap-otd and Ap-cad) are expressed differently between the sexually and asexually produced oocytes and embryos of the pea aphid. We also show, using immunohistochemistry and cytoskeletal inhibitors, that Ap-hb RNA is localized differently between sexually and asexually produced oocytes, and that this is likely due to differences in the 3' untranslated regions of the RNA. Furthermore, Ap-hb and Ap-otd have extensive expression domains in early sexually produced embryos, but are not expressed at equivalent stages in asexually produced embryos. These differences in expression likely correspond with substantial changes in the gene regulatory networks controlling early development in the pea aphid. These data imply that in the evolution of parthenogenesis a new program has evolved to control the development of asexually produced embryos, whilst retaining the existing, sexual, developmental program. The patterns of modification of these developmental processes mirror the changes that we see in developmental processes between species, in that early acting pathways in development are less constrained, and evolve faster, than later ones. We suggest that the evolution of the novel asexual development pathway in aphids is not a simple modification of an ancestral system, but the evolution of two very different developmental mechanisms occurring within a single species.
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Affiliation(s)
- Elizabeth J Duncan
- Laboratory for Evolution and Development, Genetics Otago & Gravida, National Centre for Growth and Development, Department of Biochemistry, University of Otago, 56, Dunedin 9054, Aotearoa, New Zealand.
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37
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Wilson MJ, Dearden PK. RNA localization in the honeybee (Apis mellifera) oocyte reveals insights about the evolution of RNA localization mechanisms. Dev Biol 2013; 375:193-201. [PMID: 23313731 DOI: 10.1016/j.ydbio.2013.01.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2012] [Revised: 12/21/2012] [Accepted: 01/02/2013] [Indexed: 11/28/2022]
Abstract
Subcellular localization of RNAs is a critical biological process for generation of cellular asymmetries for many cell types and a critical step in axis determination during the early development of animals. We have identified transcripts localized to the anterior and posterior of honeybee oocyte using laser capture microscopy and microarray analysis. Analysis of orthologous transcripts in Drosophila indicates that many do not show a conserved pattern of localization. By microinjecting fluorescently labeled honeybee transcripts into Drosophila egg chambers we show that these RNAs become localized in a similar manner to their localization in honeybee oocytes, indicating conservation of the localization machinery. Thus while the mechanisms for localizing RNA are conserved, the complement of localized RNAs are not. We propose that this complement of localized RNAs may change relatively rapidly through the loss or evolution of signal sequences detected by the conserved localization machinery, and show this has occurred in one transcript that is localized in a novel way in the honeybee. Our proposal, that the acquisition of novel RNA localization is relatively easy to evolve, has implications for the evolution of symmetry breaking mechanisms that trigger axis formation and development in animal embryos.
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Affiliation(s)
- Megan J Wilson
- Laboratory for Evolution and Development, Genetics Otago and Gravida, The National Centre for Growth and Development, Department of Biochemistry, University of Otago, PO Box 56, Dunedin 9054, New Zealand.
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38
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Nakao H. Anterior and posterior centers jointly regulate Bombyx embryo body segmentation. Dev Biol 2012; 371:293-301. [DOI: 10.1016/j.ydbio.2012.08.029] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2012] [Accepted: 08/28/2012] [Indexed: 11/29/2022]
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Lasko P. mRNA localization and translational control in Drosophila oogenesis. Cold Spring Harb Perspect Biol 2012; 4:cshperspect.a012294. [PMID: 22865893 DOI: 10.1101/cshperspect.a012294] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Localization of an mRNA species to a particular subcellular region can complement translational control mechanisms to produce a restricted spatial distribution of the protein it encodes. mRNA localization has been studied most in asymmetric cells such as budding yeast, early embryos, and neurons, but the process is likely to be more widespread. This article reviews the current state of knowledge about the mechanisms of mRNA localization and its functions in early embryonic development, focusing on Drosophila where the relevant knowledge is most advanced. Links between mRNA localization and translational control mechanisms also are examined.
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Affiliation(s)
- Paul Lasko
- Department of Biology, Bellini Life Sciences Building, McGill University, Montréal, Québec H3G 0B1, Canada.
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40
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van Rooijen C, Simmini S, Bialecka M, Neijts R, van de Ven C, Beck F, Deschamps J. Evolutionarily conserved requirement of Cdx for post-occipital tissue emergence. Development 2012; 139:2576-83. [PMID: 22675207 DOI: 10.1242/dev.079848] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Mouse Cdx genes are involved in axial patterning and partial Cdx mutants exhibit posterior embryonic defects. We found that mouse embryos in which all three Cdx genes are inactivated fail to generate any axial tissue beyond the cephalic and occipital primordia. Anterior axial tissues are laid down and well patterned in Cdx null embryos, and a 3' Hox gene is initially transcribed and expressed in the hindbrain normally. Axial elongation stops abruptly at the post-occipital level in the absence of Cdx, as the posterior growth zone loses its progenitor activity. Exogenous Fgf8 rescues the posterior truncation of Cdx mutants, and the spectrum of defects of Cdx null embryos matches that resulting from loss of posterior Fgfr1 signaling. Our data argue for a main function of Cdx in enforcing trunk emergence beyond the Cdx-independent cephalo-occipital region, and for a downstream role of Fgfr1 signaling in this function. Cdx requirement for the post-head section of the axis is ancestral as it takes place in arthropods as well.
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Affiliation(s)
- Carina van Rooijen
- Hubrecht Institute, Developmental Biology and Stem Cell Research, Uppsalalaan 8, 3584 CT Utrecht, and University Medical Center Utrecht, 3584 CX Utrecht, The Netherlands
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El-Sherif E, Lynch JA, Brown SJ. Comparisons of the embryonic development of Drosophila, Nasonia, and Tribolium. WILEY INTERDISCIPLINARY REVIEWS. DEVELOPMENTAL BIOLOGY 2012; 1:16-39. [PMID: 23801665 PMCID: PMC5323069 DOI: 10.1002/wdev.3] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Studying the embryogenesis of diverse insect species is crucial to understanding insect evolution. Here, we review current advances in understanding the development of two emerging model organisms: the wasp Nasonia vitripennis and the beetle Tribolium castaneum in comparison with the well-studied fruit fly Drosophila melanogaster. Although Nasonia represents the most basally branching order of holometabolous insects, it employs a derived long germband mode of embryogenesis, more like that of Drosophila, whereas Tribolium undergoes an intermediate germband mode of embryogenesis, which is more similar to the ancestral mechanism. Comparing the embryonic development and genetic regulation of early patterning events in these three insects has given invaluable insights into insect evolution. The similar mode of embryogenesis of Drosophila and Nasonia is reflected in their reliance on maternal morphogenetic gradients. However, they employ different genes as maternal factors, reflecting the evolutionary distance separating them. Tribolium, on the other hand, relies heavily on self-regulatory mechanisms other than maternal cues, reflecting its sequential nature of segmentation and the need for reiterated patterning.
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Affiliation(s)
- Ezzat El-Sherif
- Program of Genetics, Kansas State University, Manhattan, Kansas
| | - Jeremy A Lynch
- Institute for Developmental Biology, University of Cologne, Cologne, Germany
| | - Susan J Brown
- Division of Biology, Kansas State University, Manhattan, Kansas
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Abstract
The localization of mRNAs in developing animal cells is essential for establishing cellular polarity and setting up the body plan for subsequent development. Cellular and molecular mechanisms by which maternal mRNAs are localized during oogenesis have been extensively studied in Drosophila and Xenopus. In contrast, evidence for mechanisms used in the localization of mRNAs encoded by developmentally important genes has also been accumulating in several other organisms. This offers the opportunity to unravel the fundamental mechanisms of mRNA localization shared among many species, as well as unique mechanisms specifically acquired or retained by animals based on their developmental needs. In addition to maternal mRNAs, the localization of zygotically expressed mRNAs in the cells of cleaving embryos is also important for early development. In this review, mRNA localization dynamics in the oocytes/eggs of Drosophila and Xenopus are first summarized, and evidence for localized mRNAs in the oocytes/eggs and cleaving embryos of other organisms is then presented.
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Affiliation(s)
- Gaku Kumano
- Department of Biological Sciences, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan.
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Wilson MJ, Dearden PK. Diversity in insect axis formation: two orthodenticle genes and hunchback act in anterior patterning and influence dorsoventral organization in the honeybee (Apis mellifera). Development 2011; 138:3497-507. [DOI: 10.1242/dev.067926] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Axis formation is a key step in development, but studies indicate that genes involved in insect axis formation are relatively fast evolving. Orthodenticle genes have conserved roles, often with hunchback, in maternal anterior patterning in several insect species. We show that two orthodenticle genes, otd1 and otd2, and hunchback act as maternal anterior patterning genes in the honeybee (Apis mellifera) but, unlike other insects, act to pattern the majority of the anteroposterior axis. These genes regulate the expression domains of anterior, central and posterior gap genes and may directly regulate the anterior gap gene giant. We show otd1 and hunchback also influence dorsoventral patterning by regulating zerknült (zen) as they do in Tribolium, but that zen does not regulate the expression of honeybee gap genes. This suggests that interactions between anteroposterior and dorsal-ventral patterning are ancestral in holometabolous insects. Honeybee axis formation, and the function of the conserved anterior patterning gene orthodenticle, displays unique characters that indicate that, even when conserved genes pattern the axis, their regulatory interactions differ within orders of insects, consistent with relatively fast evolution in axis formation pathways.
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Affiliation(s)
- Megan J. Wilson
- Laboratory for Evolution and Development, National Research Centre for Growth and Development and Genetics Otago, Biochemistry Department, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - Peter K. Dearden
- Laboratory for Evolution and Development, National Research Centre for Growth and Development and Genetics Otago, Biochemistry Department, University of Otago, PO Box 56, Dunedin 9054, New Zealand
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Altenburger A, Martinez P, Wanninger A. Homeobox gene expression in Brachiopoda: the role of Not and Cdx in bodyplan patterning, neurogenesis, and germ layer specification. Gene Expr Patterns 2011; 11:427-36. [PMID: 21782038 DOI: 10.1016/j.gep.2011.07.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2011] [Revised: 07/01/2011] [Accepted: 07/03/2011] [Indexed: 10/18/2022]
Abstract
The molecular control that underlies brachiopod ontogeny is largely unknown. In order to contribute to this issue we analyzed the expression pattern of two homeobox containing genes, Not and Cdx, during development of the rhynchonelliform (i.e., articulate) brachiopod Terebratalia transversa. Not is a homeobox containing gene that regulates the formation of the notochord in chordates, while Cdx (caudal) is a ParaHox gene involved in the formation of posterior tissues of various animal phyla. The T. transversa homolog, TtrNot, is expressed in the ectoderm from the beginning of gastrulation until completion of larval development, which is marked by a three-lobed body with larval setae. Expression starts at gastrulation in two areas lateral to the blastopore and subsequently extends over the animal pole of the gastrula. With elongation of the gastrula, expression at the animal pole narrows to a small band, whereas the areas lateral to the blastopore shift slightly towards the future anterior region of the larva. Upon formation of the three larval body lobes, TtrNot expressing cells are present only in the posterior part of the apical lobe. Expression ceases entirely at the onset of larval setae formation. TtrNot expression is absent in unfertilized eggs, in embryos prior to gastrulation, and in settled individuals during and after metamorphosis. Comparison with the expression patterns of Not genes in other metazoan phyla suggests an ancestral role for this gene in gastrulation and germ layer (ectoderm) specification with co-opted functions in notochord formation in chordates and left/right determination in ambulacrarians and vertebrates. The caudal ortholog, TtrCdx, is first expressed in the ectoderm of the gastrulating embryo in the posterior region of the blastopore. Its expression stays stable in that domain until the blastopore is closed. Thereafter, the expression is confined to the ventral portion of the mantle lobe in the fully developed larva. No TtrCdx expression is detectable in the juvenile after metamorphosis. This expression of TtrCdx is congruent with findings in other metazoans, where genes belonging to the Cdx/caudal family are predominantly localized in posterior domains during gastrulation. Later in development this gene will play a fundamental role in the formation of posterior tissues.
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Affiliation(s)
- Andreas Altenburger
- University of Copenhagen, Natural History Museum of Denmark, Zoological Museum, Universitetsparken, Copenhagen Ø, Denmark.
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45
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Blechert O, Douglas D, Baumgartner S. Conserved function of the Krüppel gap gene in the blowfly Lucilia sericata, despite anterior shift of expression. INSECT MOLECULAR BIOLOGY 2011; 20:257-265. [PMID: 21166911 DOI: 10.1111/j.1365-2583.2010.01063.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
To determine whether expression patterns of segmentation genes found in Drosophila melanogaster can be scaled to pattern larger insects, we studied the expression of the Krüppel (Kr) gene in the blowfly Lucilia sericata. Compared with Drosophila Kr, L. sericata Kr showed an unexpected 10% shift of expression towards the anterior pole. Furthermore, expression domains not found in D. melanogaster were present at the blastoderm stage of L. sericata. To compare Kr activity and function, we employed RNA interference-mediated gene silencing. We found Kr phenotypes in L. sericata comparable with those observed in D. melanogaster, demonstrating that L. sericata Kr functions as a gap gene as it does in Drosophila. Our results show that, despite an anterior shift in expression, Kr function has remained conserved during the evolution of the blowflies.
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Affiliation(s)
- O Blechert
- Lund University, Department of Experimental Medical Sciences, Lund, Sweden
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46
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Peel AD, Averof M. Early asymmetries in maternal transcript distribution associated with a cortical microtubule network and a polar body in the beetle Tribolium castaneum. Dev Dyn 2011; 239:2875-87. [PMID: 20857499 DOI: 10.1002/dvdy.22423] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The localization of maternal mRNAs during oogenesis plays a central role in axial specification in some insects. Here we describe a polar body-associated asymmetry in maternal transcript distribution in pre-blastoderm eggs of the beetle Tribolium castaneum. Since the position of the polar body marks the future dorsal side of the embryo, we have investigated whether this asymmetry in mRNA distribution plays a role in dorsal-ventral axis specification. Whilst our results suggest polar body-associated transcripts do not play a significant role in specifying the DV axis, at least during early embryogenesis, we do find that the polar body is closely associated with a cortical microtubule network (CMN), which may play a role in the localization of transcripts during oogenesis. Transcripts of the gene T.c.pangolin co-localize with the CMN at the time of their anterior localization during oogenesis and their anterior localization is disrupted by the microtubule-depolymerizing agent colcemid.
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Affiliation(s)
- Andrew D Peel
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology Hellas, Crete, Greece.
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47
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Lasko P. Posttranscriptional regulation in Drosophila oocytes and early embryos. WILEY INTERDISCIPLINARY REVIEWS-RNA 2011; 2:408-16. [PMID: 21957026 DOI: 10.1002/wrna.70] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Molecular asymmetries underlying embryonic axis patterning and germ cell specification are established in Drosophila largely by position-dependent translational regulation of maternally expressed messenger RNAs. Here, I review several mechanisms of posttranscriptional regulation in the Drosophila oocyte and syncytial embryo, and how they relate to embryonic patterning, with a strong emphasis on the most recent advances in the area. The review is not exhaustive, but focuses on examples that illustrate the interplay between specific regulatory events and the general metabolic machinery that governs translation and mRNA stability. Biophysical investigations into how the Bicoid gradient is formed are discussed, as are the elaborate mechanisms controlling how the Oskar and Nanos proteins become restricted to the posterior pole of the embryo. Work on Vasa, a translational activator of some germ line mRNAs and on 4EHP, a negative regulator that unproductively binds the 5' cap structure of target mRNAs, is also briefly reviewed. Finally, the emerging understanding of the role of microRNAs in regulating translation of germ line mRNAs is also discussed.
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Affiliation(s)
- Paul Lasko
- Department of Biology, McGill University, Montreal, Quebec, Canada.
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48
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Abstract
Gap genes are involved in segment determination during the early development of the fruit fly Drosophila melanogaster as well as in other insects. This review attempts to synthesize the current knowledge of the gap gene network through a comprehensive survey of the experimental literature. I focus on genetic and molecular evidence, which provides us with an almost-complete picture of the regulatory interactions responsible for trunk gap gene expression. I discuss the regulatory mechanisms involved, and highlight the remaining ambiguities and gaps in the evidence. This is followed by a brief discussion of molecular regulatory mechanisms for transcriptional regulation, as well as precision and size-regulation provided by the system. Finally, I discuss evidence on the evolution of gap gene expression from species other than Drosophila. My survey concludes that studies of the gap gene system continue to reveal interesting and important new insights into the role of gene regulatory networks in development and evolution.
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Affiliation(s)
- Johannes Jaeger
- Centre de Regulació Genòmica, Universtitat Pompeu Fabra, Barcelona, Spain.
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49
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Lynch JA, Desplan C. Novel modes of localization and function of nanos in the wasp Nasonia. Development 2010; 137:3813-21. [PMID: 20929949 DOI: 10.1242/dev.054213] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Abdominal patterning in Drosophila requires the function of nanos (nos) to prevent translation of hunchback (hb) mRNA in the posterior of the embryo. nos function is restricted to the posterior by the translational repression of mRNA that is not incorporated into the posteriorly localized germ plasm during oogenesis. The wasp Nasonia vitripennis (Nv) undergoes a long germ mode of development very similar to Drosophila, although the molecular patterning mechanisms employed in these two organisms have diverged significantly, reflecting the independent evolution of this mode of development. Here, we report that although Nv nanos (Nv-nos) has a conserved function in embryonic patterning through translational repression of hb, the timing and mechanisms of this repression are significantly delayed in the wasp compared with the fly. This delay in Nv-nos function appears to be related to the dynamic behavior of the germ plasm in Nasonia, as well as to the maternal provision of Nv-Hb protein during oogenesis. Unlike in flies, there appears to be two functional populations of Nv-nos mRNA: one that is concentrated in the oosome and is taken up into the pole cells before evidence of Nv-hb repression is observed; another that forms a gradient at the posterior and plays a role in Nv-hb translational repression. Altogether, our results show that, although the embryonic patterning function of nos orthologs is broadly conserved, the mechanisms employed to achieve this function are distinct.
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Affiliation(s)
- Jeremy A Lynch
- Center for Developmental Genetics, Department of Biology, New York University, New York, NY 10003, USA.
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50
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García-Solache M, Jaeger J, Akam M. A systematic analysis of the gap gene system in the moth midge Clogmia albipunctata. Dev Biol 2010; 344:306-18. [DOI: 10.1016/j.ydbio.2010.04.019] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2009] [Revised: 04/19/2010] [Accepted: 04/21/2010] [Indexed: 02/04/2023]
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