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Lev O, Edgecombe GD, Chipman AD. Serial Homology and Segment Identity in the Arthropod Head. Integr Org Biol 2022; 4:obac015. [PMID: 35620450 PMCID: PMC9128542 DOI: 10.1093/iob/obac015] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The anterior-most unit of the crown-group arthropod body plan includes three segments, the pre-gnathal segments, that contain three neuromeres that together comprise the brain. Recent work on the development of this anterior region has shown that its three units exhibit many developmental differences to the more posterior segments, to the extent that they should not be considered serial homologs. Building on this revised understanding of the development of the pre-gnathal segments, we suggest a novel scenario for arthropod head evolution. We posit an expansion of an ancestral single-segmented head at the transition from Radiodonta to Deuteropoda in the arthropod stem group. The expanded head subdivided into three segmental units, each maintaining some of the structures of the ancestral head. This scenario is consistent with what we know of head evolution from the fossil record and helps reconcile some of the debates about early arthropod evolution.
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Affiliation(s)
- Oren Lev
- The Dept. of Ecology, Evolution & Behavior, The Silberman Institute of Life Sciences, The Hebrew University of Jerusalem
| | - Gregory D Edgecombe
- Department of Earth Sciences, The Natural History Museum, Cromwell Road, London SW7 5BD, UK
| | - Ariel D Chipman
- The Dept. of Ecology, Evolution & Behavior, The Silberman Institute of Life Sciences, The Hebrew University of Jerusalem
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2
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Lev O, Chipman AD. Development of the Pre-gnathal Segments in the Milkweed Bug Oncopeltus fasciatus Suggests They Are Not Serial Homologs of Trunk Segments. Front Cell Dev Biol 2021; 9:695135. [PMID: 34422818 PMCID: PMC8378449 DOI: 10.3389/fcell.2021.695135] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Accepted: 07/19/2021] [Indexed: 12/30/2022] Open
Abstract
The three anterior-most segments in arthropods contain the ganglia that make up the arthropod brain. These segments, the pre-gnathal segments (PGS), are known to exhibit many developmental differences to other segments, believed to reflect their divergent morphology. We have analyzed the expression and function of the genes involved in the conserved segment-polarity network, including genes from the Wnt and Hedgehog pathways, in the PGS, compared with the trunk segments, in the hemimetabolous insect Oncopeltus fasciatus. Gene function was tested by manipulating expression through RNA interference against components of the two pathways. We show that there are fundamental differences in the expression patterns of the segment polarity genes, in the timing of their expression and in the interactions among them in the process of pre-gnathal segment generation, relative to all other segments. We argue that given these differences, the PGS should not be considered serially homologous to trunk segments. This realization raises important questions about the differing evolutionary ancestry of different regions of the arthropod head.
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Affiliation(s)
| | - Ariel D. Chipman
- Department of Ecology, Evolution and Behavior, Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
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Chipman AD, Edgecombe GD. Developing an integrated understanding of the evolution of arthropod segmentation using fossils and evo-devo. Proc Biol Sci 2019; 286:20191881. [PMID: 31575373 DOI: 10.1098/rspb.2019.1881] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Segmentation is fundamental to the arthropod body plan. Understanding the evolutionary steps by which arthropods became segmented is being transformed by the integration of data from evolutionary developmental biology (evo-devo), Cambrian fossils that allow the stepwise acquisition of segmental characters to be traced in the arthropod stem-group, and the incorporation of fossils into an increasingly well-supported phylogenetic framework for extant arthropods based on genomic-scale datasets. Both evo-devo and palaeontology make novel predictions about the evolution of segmentation that serve as testable hypotheses for the other, complementary data source. Fossils underpin such hypotheses as arthropodization originating in a frontal appendage and then being co-opted into other segments, and segmentation of the endodermal midgut in the arthropod stem-group. Insights from development, such as tagmatization being associated with different modes of segment generation in different body regions, and a distinct patterning of the anterior head segments, are complemented by palaeontological evidence for the pattern of tagmatization during ontogeny of exceptionally preserved fossils. Fossil and developmental data together provide evidence for a short head in stem-group arthropods and the mechanism of its formation and retention. Future breakthroughs are expected from identification of molecular signatures of developmental innovations within a phylogenetic framework, and from a focus on later developmental stages to identify the differentiation of repeated units of different systems within segmental precursors.
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Affiliation(s)
- Ariel D Chipman
- Department of Ecology, Evolution and Behavior, The Silberman Institute of Life Sciences, Edmond J. Safra Campus - Givat Ram, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Gregory D Edgecombe
- Department of Earth Sciences, The Natural History Museum, Cromwell Road, London SW7 5BD, UK
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4
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Bridi JC, Ludlow ZN, Hirth F. Lineage-specific determination of ring neuron circuitry in the central complex of Drosophila. Biol Open 2019; 8:bio.045062. [PMID: 31285267 PMCID: PMC6679397 DOI: 10.1242/bio.045062] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The ellipsoid body (EB) of the Drosophila central complex mediates sensorimotor integration and action selection for adaptive behaviours. Insights into its physiological function are steadily accumulating, however the developmental origin and genetic specification have remained largely elusive. Here we identify two stem cells in the embryonic neuroectoderm as precursor cells of neuronal progeny that establish EB circuits in the adult brain. Genetic tracing of embryonic neuroblasts ppd5 and mosaic analysis with a repressible cell marker identified lineage-related progeny as Pox neuro (Poxn)-expressing EB ring neurons, R1-R4. During embryonic brain development, engrailed function is required for the initial formation of Poxn-expressing ppd5-derived progeny. Postembryonic determination of R1-R4 identity depends on lineage-specific Poxn function that separates neuronal subtypes of ppd5-derived progeny into hemi-lineages with projections either terminating in the EB ring neuropil or the superior protocerebrum (SP). Poxn knockdown in ppd5-derived progeny results in identity transformation of engrailed-expressing hemi-lineages from SP to EB-specific circuits. In contrast, lineage-specific knockdown of engrailed leads to reduced numbers of Poxn-expressing ring neurons. These findings establish neuroblasts ppd5-derived ring neurons as lineage-related sister cells that require engrailed and Poxn function for the proper formation of EB circuitry in the adult central complex of Drosophila.
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Affiliation(s)
- Jessika C Bridi
- Department of Basic and Clinical Neuroscience, Maurice Wohl Clinical Neuroscience Institute, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE5 9RX, United Kingdom
| | - Zoe N Ludlow
- Department of Basic and Clinical Neuroscience, Maurice Wohl Clinical Neuroscience Institute, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE5 9RX, United Kingdom
| | - Frank Hirth
- Department of Basic and Clinical Neuroscience, Maurice Wohl Clinical Neuroscience Institute, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London SE5 9RX, United Kingdom
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Hemmi N, Akiyama-Oda Y, Fujimoto K, Oda H. A quantitative study of the diversity of stripe-forming processes in an arthropod cell-based field undergoing axis formation and growth. Dev Biol 2018; 437:84-104. [DOI: 10.1016/j.ydbio.2018.03.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2017] [Revised: 03/01/2018] [Accepted: 03/01/2018] [Indexed: 12/25/2022]
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Liu H, Liu Q, Zhou X, Huang Y, Zhang Z. Genome Editing of Wnt-1, a Gene Associated with Segmentation, via CRISPR/Cas9 in the Pine Caterpillar Moth, Dendrolimus punctatus. Front Physiol 2017; 7:666. [PMID: 28111552 PMCID: PMC5216022 DOI: 10.3389/fphys.2016.00666] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2016] [Accepted: 12/19/2016] [Indexed: 01/11/2023] Open
Abstract
The pine caterpillar moth, Dendrolimus punctatus, is a devastating forest pest. Genetic manipulation of this insect pest is limited due to the lack of genomic and functional genomic toolsets. Recently, CRISPR/Cas9 technology has been demonstrated to be a promising approach to modify the genome. To investigate gene functions during the embryogenesis, we introduced CRISPR/Cas9 system in D. punctatus to precisely and effectively manipulate gene expressions inmutant embryos. Compared to controls, knocking out of DpWnt-1, a gene well known for its role in the early body planning, led to high embryonic mortality. Among these mutants, 32.9% of the embryos and larvae showed an abnormal development. DpWnt-1 mutants predominantly exhibited abnormal posterior segments. In addition, multiple phenotypes were observed, including the loss of limbs and the head deformation, suggesting that DpWnt-1 signaling pathway is necessary for anterior segmentation and appendage development. Overall, our results demonstrate that CRISPR/Cas9 system is feasible and efficient in inducing mutations at a specific locus in D. punctatus. This study not only lays the foundation for characterizing gene functions in a non-model species, but also facilitates the future development of pest control alternatives for a major defoliator.
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Affiliation(s)
- Huihui Liu
- Key Laboratory of Forest Protection, Research Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry, State Forestry Administration Beijing, China
| | - Qun Liu
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences Shanghai, China
| | - Xuguo Zhou
- Department of Entomology, University of Kentucky Lexington, KY, USA
| | - Yongping Huang
- Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences Shanghai, China
| | - Zhen Zhang
- Key Laboratory of Forest Protection, Research Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry, State Forestry Administration Beijing, China
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Oberhofer G, Grossmann D, Siemanowski JL, Beissbarth T, Bucher G. Wnt/β-catenin signaling integrates patterning and metabolism of the insect growth zone. Development 2014; 141:4740-50. [PMID: 25395458 PMCID: PMC4299277 DOI: 10.1242/dev.112797] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Wnt/β-catenin and hedgehog (Hh) signaling are essential for transmitting signals across cell membranes in animal embryos. Early patterning of the principal insect model, Drosophila melanogaster, occurs in the syncytial blastoderm, where diffusion of transcription factors obviates the need for signaling pathways. However, in the cellularized growth zone of typical short germ insect embryos, signaling pathways are predicted to play a more fundamental role. Indeed, the Wnt/β-catenin pathway is required for posterior elongation in most arthropods, although which target genes are activated in this context remains elusive. Here, we use the short germ beetle Tribolium castaneum to investigate two Wnt and Hh signaling centers located in the head anlagen and in the growth zone of early embryos. We find that Wnt/β-catenin signaling acts upstream of Hh in the growth zone, whereas the opposite interaction occurs in the head. We determine the target gene sets of the Wnt/β-catenin and Hh pathways and find that the growth zone signaling center activates a much greater number of genes and that the Wnt and Hh target gene sets are essentially non-overlapping. The Wnt pathway activates key genes of all three germ layers, including pair-rule genes, and Tc-caudal and Tc-twist. Furthermore, the Wnt pathway is required for hindgut development and we identify Tc-senseless as a novel hindgut patterning gene required in the early growth zone. At the same time, Wnt acts on growth zone metabolism and cell division, thereby integrating growth with patterning. Posterior Hh signaling activates several genes potentially involved in a proteinase cascade of unknown function.
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Affiliation(s)
- Georg Oberhofer
- Department of Evolutionary Developmental Biology, Johann Friedrich Blumenbach Institute of Zoology and Anthropology, Georg-August-University, Justus von Liebig Weg 11, Göttingen D-37077, Germany
| | - Daniela Grossmann
- Department of Evolutionary Developmental Biology, Johann Friedrich Blumenbach Institute of Zoology and Anthropology, Georg-August-University, Justus von Liebig Weg 11, Göttingen D-37077, Germany
| | - Janna L Siemanowski
- Department of Evolutionary Developmental Biology, Johann Friedrich Blumenbach Institute of Zoology and Anthropology, Georg-August-University, Justus von Liebig Weg 11, Göttingen D-37077, Germany
| | - Tim Beissbarth
- Department of Medical Statistics, University Medical Center Göttingen, Humboldtallee 32, Göttingen D-37073, Germany
| | - Gregor Bucher
- Department of Evolutionary Developmental Biology, Johann Friedrich Blumenbach Institute of Zoology and Anthropology, Georg-August-University, Justus von Liebig Weg 11, Göttingen D-37077, Germany
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Peel AD, Schanda J, Grossmann D, Ruge F, Oberhofer G, Gilles AF, Schinko JB, Klingler M, Bucher G. Tc-knirps plays different roles in the specification of antennal and mandibular parasegment boundaries and is regulated by a pair-rule gene in the beetle Tribolium castaneum. BMC DEVELOPMENTAL BIOLOGY 2013; 13:25. [PMID: 23777260 PMCID: PMC3698154 DOI: 10.1186/1471-213x-13-25] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Accepted: 06/12/2013] [Indexed: 01/03/2023]
Abstract
Background The Drosophila larval head is evolutionarily derived at the genetic and morphological level. In the beetle Tribolium castaneum, development of the larval head more closely resembles the ancestral arthropod condition. Unlike in Drosophila, a knirps homologue (Tc-kni) is required for development of the antennae and mandibles. However, published Tc-kni data are restricted to cuticle phenotypes and Tc-even-skipped and Tc-wingless stainings in knockdown embryos. Hence, it has remained unclear whether the entire antennal and mandibular segments depend on Tc-kni function, and whether the intervening intercalary segment is formed completely. We address these questions with a detailed examination of Tc-kni function. Results By examining the expression of marker genes in RNAi embryos, we show that Tc-kni is required only for the formation of the posterior parts of the antennal and mandibular segments (i.e. the parasegmental boundaries). Moreover, we find that the role of Tc-kni is distinct in these segments: Tc-kni is required for the initiation of the antennal parasegment boundary, but only for the maintenance of the mandibular parasegmental boundary. Surprisingly, Tc-kni controls the timing of expression of the Hox gene Tc-labial in the intercalary segment, although this segment does form in the absence of Tc-kni function. Unexpectedly, we find that the pair-rule gene Tc-even-skipped helps set the posterior boundary of Tc-kni expression in the mandible. Using the mutant antennaless, a likely regulatory Null mutation at the Tc-kni locus, we provide evidence that our RNAi studies represent a Null situation. Conclusions Tc-kni is required for the initiation of the antennal and the maintenance of the mandibular parasegmental boundaries. Tc-kni is not required for specification of the anterior regions of these segments, nor the intervening intercalary segment, confirming that Tc-kni is not a canonical ‘gap-gene’. Our finding that a gap gene orthologue is regulated by a pair rule gene adds to the view that the segmentation gene hierarchies differ between Tribolium and Drosophila upstream of the pair rule gene level. In Tribolium, as in Drosophila, head and trunk segmentation gene networks cooperate to pattern the mandibular segment, albeit involving Tc-kni as novel component.
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Affiliation(s)
- Andrew D Peel
- Institute of Molecular Biology and Biotechnology (IMBB), Foundation for Research and Technology - Hellas (FoRTH), Nikolaou Plastira 100, GR-70013, Heraklion, Crete, Greece
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9
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Kuo DH, Shankland M, Weisblat DA. Regional differences in BMP-dependence of dorsoventral patterning in the leech Helobdella. Dev Biol 2012; 368:86-94. [PMID: 22641012 PMCID: PMC3398150 DOI: 10.1016/j.ydbio.2012.05.021] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2012] [Revised: 05/17/2012] [Accepted: 05/20/2012] [Indexed: 11/26/2022]
Abstract
In the leech Helobdella, the ectoderm exhibits a high degree of morphological homonomy between body segments, but pattern elements in lateral ectoderm arise via distinct cell lineages in the segments of the rostral and midbody regions. In each of the four rostral segments, a complete set of ventrolateral (O fate) and dorsolateral (P fate) ectodermal pattern elements arises from a single founder cell, op. In the 28 midbody and caudal segments, however, there are two initially indeterminate o/p founder cells; the more dorsal of these is induced to adopt the P fate by BMP5-8 emanating from the dorsalmost ectoderm, while the more ventral cell assumes the O fate. Previous work has suggested that the dorsoventral patterning of O and P fates differs in the rostral region, but the role of BMP signaling in those segments has not been investigated. We show here that suppression of dorsal BMP5-8 signaling (which effects a P-to-O fate change in the midbody) has no effect on the patterning of O and P fates in the rostral region. Furthermore, ectopic expression of BMP5-8 in the ventral ectoderm (which induces an O-to-P fate change in the midbody) has no effect in the rostral region. Finally, expression of a dominant-negative BMP receptor (which induces a P-to-O fate change in the midbody) fails to affect O/P patterning in the rostral region. Thus, the rostral segments appear to use some mechanism other than BMP signaling to pattern O and P cell fates along the dorsoventral axis. From a mechanistic standpoint, the OP lineage of the rostral segments and the O-P equivalence group of the midbody and caudal segments constitute distinct developmental modules that rely to differing degrees on positional cues from surrounding ectoderm in order to specify homonomous cell fates.
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Affiliation(s)
- Dian-Han Kuo
- Graduate Program in Zoology, School of Biological Sciences, The University of Texas at Austin, Austin, TX 78712, USA.
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Heat shock-mediated misexpression of genes in the beetle Tribolium castaneum. Dev Genes Evol 2012; 222:287-98. [DOI: 10.1007/s00427-012-0412-x] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2012] [Accepted: 06/29/2012] [Indexed: 12/18/2022]
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Posnien N, Koniszewski NDB, Hein HJ, Bucher G. Candidate gene screen in the red flour beetle Tribolium reveals six3 as ancient regulator of anterior median head and central complex development. PLoS Genet 2011; 7:e1002416. [PMID: 22216011 PMCID: PMC3245309 DOI: 10.1371/journal.pgen.1002416] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2011] [Accepted: 10/13/2011] [Indexed: 11/19/2022] Open
Abstract
Several highly conserved genes play a role in anterior neural plate patterning of vertebrates and in head and brain patterning of insects. However, head involution in Drosophila has impeded a systematic identification of genes required for insect head formation. Therefore, we use the red flour beetle Tribolium castaneum in order to comprehensively test the function of orthologs of vertebrate neural plate patterning genes for a function in insect head development. RNAi analysis reveals that most of these genes are indeed required for insect head capsule patterning, and we also identified several genes that had not been implicated in this process before. Furthermore, we show that Tc-six3/optix acts upstream of Tc-wingless, Tc-orthodenticle1, and Tc-eyeless to control anterior median development. Finally, we demonstrate that Tc-six3/optix is the first gene known to be required for the embryonic formation of the central complex, a midline-spanning brain part connected to the neuroendocrine pars intercerebralis. These functions are very likely conserved among bilaterians since vertebrate six3 is required for neuroendocrine and median brain development with certain mutations leading to holoprosencephaly.
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Affiliation(s)
- Nico Posnien
- Center for Molecular Physiology of the Brain (CMPB), Göttingen Center of Molecular Biology, Caspari-Haus, Georg-August-University Göttingen, Göttingen, Germany
- School of Life Sciences, Oxford Brookes University, Oxford, United Kingdom
| | - Nikolaus Dieter Bernhard Koniszewski
- Center for Molecular Physiology of the Brain (CMPB), Göttingen Center of Molecular Biology, Caspari-Haus, Georg-August-University Göttingen, Göttingen, Germany
| | | | - Gregor Bucher
- Center for Molecular Physiology of the Brain (CMPB), Göttingen Center of Molecular Biology, Caspari-Haus, Georg-August-University Göttingen, Göttingen, Germany
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Ntini E, Wimmer EA. Second order regulator Collier directly controls intercalary-specific segment polarity gene expression. Dev Biol 2011; 360:403-14. [PMID: 22005665 DOI: 10.1016/j.ydbio.2011.09.035] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2011] [Revised: 09/28/2011] [Accepted: 09/29/2011] [Indexed: 01/19/2023]
Abstract
In Drosophila, trunk metamerization is established by a cascade of segmentation gene activities: the gap genes, the pair rule genes, and the segment polarity genes. In the anterior head, metamerization requires also gap-like genes and segment polarity genes. However, because the pair rule genes are not active in this part of the embryo, the question on which gene activities are fulfilling the role of the second order regulator genes still remains to be solved. Here we provide first molecular evidence that the Helix-Loop-Helix-COE transcription factor Collier fulfills this role by directly activating the expression of the segment polarity gene hedgehog in the posterior part of the intercalary segment. Collier thereby occupies a newly identified binding site within an intercalary-specific cis-regulatory element. Moreover, we identified a direct physical association between Collier and the basic-leucine-zipper transcription factor Cap'n'collar B, which seems to restrict the activating input of Collier to the posterior part of the intercalary segment and to lead to the attenuation of hedgehog expression in the intercalary lobes at later stages.
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Affiliation(s)
- Evgenia Ntini
- Department of Developmental Biology, Johann-Friedrich-Blumenbach-Institute of Zoology und Anthropology, Georg-August-University Göttingen, GZMB, Ernst-Caspari-Haus, Justus-von-Liebig-Weg 11, 37077 Göttingen, Germany
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13
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Ntini E, Wimmer EA. Unique establishment of procephalic head segments is supported by the identification of cis-regulatory elements driving segment-specific segment polarity gene expression in Drosophila. Dev Genes Evol 2011; 221:1-16. [PMID: 21399984 PMCID: PMC3089733 DOI: 10.1007/s00427-011-0354-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2011] [Accepted: 02/10/2011] [Indexed: 12/20/2022]
Abstract
Anterior head segmentation is governed by different regulatory mechanisms than those that control trunk segmentation in Drosophila. For segment polarity genes, both initial mode of activation as well as cross-regulatory interactions among them differ from the typical genetic circuitry in the trunk and are unique for each of the procephalic segments. In order to better understand the segment-specific gene network responsible for the procephalic expression of the earliest active segment polarity genes wingless and hedgehog, we started to identify and analyze cis-regulatory DNA elements of these genes. For hedgehog, we could identify a cis-regulatory element, ic-CRE, that mediates expression specifically in the posterior part of the intercalary segment and requires promoter-specific interaction for its function. The intercalary stripe is the last part of the metameric hedgehog expression pattern that appears during embryonic development, which probably reflects the late and distinct establishment of this segment. The identification of a cis-regulatory element that is specific for one head segment supports the mutant-based observation that the expression of segment polarity genes is governed by a unique gene network in each of the procephalic segments. This provides further indication that the anterior-most head segments represent primary segments, which are set up independently, in contrast to the secondary segments of the trunk, which resemble true repetitive units.
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Affiliation(s)
- Evgenia Ntini
- Department of Developmental Biology, Johann-Friedrich-Blumenbach-Institute of Zoology und Anthropology, Georg-August-University Göttingen, GZMB, Ernst-Caspari-Haus, Justus-von-Liebig-Weg 11, 37077, Göttingen, Germany
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Janssen R, Damen WG, Budd GE. Expression of collier in the premandibular segment of myriapods: support for the traditional Atelocerata concept or a case of convergence? BMC Evol Biol 2011; 11:50. [PMID: 21349177 PMCID: PMC3053236 DOI: 10.1186/1471-2148-11-50] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2010] [Accepted: 02/24/2011] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND A recent study on expression and function of the ortholog of the Drosophila collier (col) gene in various arthropods including insects, crustaceans and chelicerates suggested a de novo function of col in the development of the appendage-less intercalary segment of insects. However, this assumption was made on the background of the now widely-accepted Pancrustacea hypothesis that hexapods represent an in-group of the crustaceans. It was therefore assumed that the expression of col in myriapods would reflect the ancestral state like in crustaceans and chelicerates, i.e. absence from the premandibular/intercalary segment and hence no function in its formation. RESULTS We find that col in myriapods is expressed at early developmental stages in the same anterior domain in the head, the parasegment 0, as in insects. Comparable early expression of col is not present in the anterior head of an onychophoran that serves as an out-group species closely related to the arthropods. CONCLUSIONS Our findings suggest either that i) the function of col in head development has been conserved between insects and myriapods, and that these two classes of arthropods may be closely related supporting the traditional Atelocerata (or Tracheata) hypothesis; or ii) alternatively col function could have been lost in early head development in crustaceans, or may indeed have evolved convergently in insects and myriapods.
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Affiliation(s)
- Ralf Janssen
- Uppsala University, Department of Earth Sciences, Villavägen 16, 752 36 Uppsala, Sweden.
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15
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Posnien N, Schinko JB, Kittelmann S, Bucher G. Genetics, development and composition of the insect head--a beetle's view. ARTHROPOD STRUCTURE & DEVELOPMENT 2010; 39:399-410. [PMID: 20800703 DOI: 10.1016/j.asd.2010.08.002] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2010] [Revised: 08/08/2010] [Accepted: 08/15/2010] [Indexed: 05/29/2023]
Abstract
Many questions regarding evolution and ontogeny of the insect head remain open. Likewise, the genetic basis of insect head development is poorly understood. Recently, the investigation of gene expression data and the analysis of patterning gene function have revived interest in insect head development. Here, we argue that the red flour beetle Tribolium castaneum is a well suited model organism to spearhead research with respect to the genetic control of insect head development. We review recent molecular data and discuss its bearing on early development and morphogenesis of the head. We present a novel hypothesis on the ontogenetic origin of insect head sutures and review recent insights into the question on the origin of the labrum. Further, we argue that the study of developmental genes may identify the elusive anterior non-segmental region and present some evidence in favor of its existence. With respect to the question of evolution of patterning we show that the head Anlagen of the fruit fly Drosophila melanogaster and Tribolium differ considerably and we review profound differences of their genetic regulation. Finally, we discuss which insect model species might help us to answer the open questions concerning the genetic regulation of head development and its evolution.
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Affiliation(s)
- Nico Posnien
- Institute for Population Genetics, University of Veterinary Medicine Vienna, Veterinärplatz 1, Vienna, Austria
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16
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Posnien N, Bucher G. Formation of the insect head involves lateral contribution of the intercalary segment, which depends on Tc-labial function. Dev Biol 2009; 338:107-16. [PMID: 19913530 DOI: 10.1016/j.ydbio.2009.11.010] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2009] [Revised: 10/20/2009] [Accepted: 11/06/2009] [Indexed: 10/20/2022]
Abstract
The insect head is composed of several segments. During embryonic development, the segments fuse to form a rigid head capsule where obvious segmental boundaries are lacking. Hence, the assignment of regions of the insect head to specific segments is hampered, especially with respect to dorsal (vertex) and lateral (gena) parts. We show that upon Tribolium labial (Tc-lab) knock down, the intercalary segment is deleted but not transformed. Furthermore, we find that the intercalary segment contributes to lateral parts of the head cuticle in Tribolium. Based on several additional mutant and RNAi phenotypes that interfere with gnathal segment development, we show that these segments do not contribute to the dorsal head capsule apart from the dorsal ridge. Opposing the classical view but in line with findings in the vinegar fly Drosophila melanogaster and the milkweed bug Oncopeltus fasciatus, we propose a "bend and zipper" model for insect head capsule formation.
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Affiliation(s)
- Nico Posnien
- Department of Developmental Biology, Johann Friedrich Blumenbach Institute of Zoology and Anthropology, Georg-August-University, 37077 Göttingen, Germany
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17
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Urbach R, Volland D, Seibert J, Technau GM. Segment-specific requirements for dorsoventral patterning genes during early brain development in Drosophila. Development 2007; 133:4315-30. [PMID: 17038517 DOI: 10.1242/dev.02605] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
An initial step in the development of the Drosophila central nervous system is the delamination of a stereotype population of neural stem cells (neuroblasts, NBs) from the neuroectoderm. Expression of the columnar genes ventral nervous system defective (vnd), intermediate neuroblasts defective (ind) and muscle segment homeobox (msh) subdivides the truncal neuroectoderm (primordium of the ventral nerve cord) into a ventral, intermediate and dorsal longitudinal domain, and has been shown to play a key role in the formation and/or specification of corresponding NBs. In the procephalic neuroectoderm (pNE, primordium of the brain), expression of columnar genes is highly complex and dynamic, and their functions during brain development are still unknown. We have investigated the role of these genes (with special emphasis on the Nkx2-type homeobox gene vnd) in early embryonic development of the brain. We show at the level of individually identified cells that vnd controls the formation of ventral brain NBs and is required, and to some extent sufficient, for the specification of ventral and intermediate pNE and deriving NBs. However, we uncovered significant differences in the expression of and regulatory interactions between vnd, ind and msh among brain segments, and in comparison to the ventral nerve cord. Whereas in the trunk Vnd negatively regulates ind, Vnd does not repress ind (but does repress msh) in the ventral pNE and NBs. Instead, in the deutocerebral region, Vnd is required for the expression of ind. We also show that, in the anterior brain (protocerebrum), normal production of early glial cells is independent from msh and vnd, in contrast to the posterior brain (deuto- and tritocerebrum) and to the ventral nerve cord.
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Affiliation(s)
- Rolf Urbach
- Institute of Genetics, University of Mainz, D-55099 Mainz, Germany.
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18
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Liu Z, Yang X, Dong Y, Friedrich M. Tracking down the "head blob": comparative analysis of wingless expression in the developing insect procephalon reveals progressive reduction of embryonic visual system patterning in higher insects. ARTHROPOD STRUCTURE & DEVELOPMENT 2006; 35:341-356. [PMID: 18089080 DOI: 10.1016/j.asd.2006.07.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2006] [Accepted: 07/05/2006] [Indexed: 05/25/2023]
Abstract
The evolution of larval head morphology in holometabolous insects is characterized by reduction of antennal appendages and the visual system components. Little insight has been gained into molecular developmental changes underlying this morphological diversification. Here we compare the expression of the segment polarity gene wingless (wg) in the pregnathal head of fruit fly, flour beetle and grasshopper embryos. We provide evidence that wg activity contributes to segment border formation, and, subsequently, the separation of the visual system and protocerebrum anlagen in the anterior procephalon. In directly developing insects like grasshopper, seven expression domains are formed during this process. The activation of four of these, which correspond to polar expression pairs in the optic lobe anlagen and the protocerebral ectoderm, has shifted to postembryonic stages in flour beetle and Drosophila. The remaining three domains map to the protocerebral neuroectoderm, and form by disintegration of a large precursor domain in flour beetle and grasshopper. In Drosophila, the precursor domain remains intact, constituting the previously described "head blob". These data document major changes in the expression of an early patterning gene correlated with the dramatic evolution of embryonic visual system development in the Holometabola.
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Affiliation(s)
- Zhenyi Liu
- Department of Molecular Biology and Pharmacology, Washington University in St Louis School of Medicine, 3600 Cancer Research Building, 660 S. Euclid Ave, St. Louis, MO 63110, USA
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19
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Ober KA, Jockusch EL. The roles of wingless and decapentaplegic in axis and appendage development in the red flour beetle, Tribolium castaneum. Dev Biol 2006; 294:391-405. [PMID: 16616738 DOI: 10.1016/j.ydbio.2006.02.053] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2005] [Revised: 11/29/2005] [Accepted: 02/28/2006] [Indexed: 01/09/2023]
Abstract
Axis patterning and appendage development have been well studied in Drosophila melanogaster, a species in which both limb and segment morphogenesis are derived. In Drosophila, positional information from genes important in anteroposterior and dorsoventral axis formation, including wingless (wg) and decapentaplegic (dpp), is required for allocating and patterning the appendage primordia. We used RNA interference to characterize the functions of wg and dpp in the red flour beetle, Tribolium castaneum, which retains more ancestral modes of limb and segment morphogenesis. We also characterized the expression of potential targets of the WG and DPP signaling pathways in these embryos. Tribolium embryos in which dpp had been downregulated had defects in the dorsalmost body wall, but did not appear to have been globally repatterned and had normal appendages. Downregulation of wg led to the loss of segment boundaries, gnathal and thoracic appendages, and lateral head lobes, and to changes in the expression of dpp, Distal-less, and Engrailed. The functions of wg varied along both the anteroposterior and dorsoventral axes of the embryo. Phylogenetic comparisons indicate that the role of WNT signaling in segment boundary formation is evolutionarily old, but that its role in appendage allocation originated in the common ancestor of holometabolous insects.
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Affiliation(s)
- Karen A Ober
- Department of Ecology and Evolutionary Biology, 75 N. Eagleville Rd., U-3043, University of Connecticut, Storrs, CT 06269, USA
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20
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Jockusch EL, Ober KA. Hypothesis Testing in Evolutionary Developmental Biology: A Case Study from Insect Wings. J Hered 2004; 95:382-96. [PMID: 15388766 DOI: 10.1093/jhered/esh064] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Developmental data have the potential to give novel insights into morphological evolution. Because developmental data are time-consuming to obtain, support for hypotheses often rests on data from only a few distantly related species. Similarities between these distantly related species are parsimoniously inferred to represent ancestral aspects of development. However, with limited taxon sampling, ancestral similarities in developmental patterning can be difficult to distinguish from similarities that result from convergent co-option of developmental networks, which appears to be common in developmental evolution. Using a case study from insect wings, we discuss how these competing explanations for similarity can be evaluated. Two kinds of developmental data have recently been used to support the hypothesis that insect wings evolved by modification of limb branches that were present in ancestral arthropods. This support rests on the assumption that aspects of wing development in Drosophila, including similarities to crustacean epipod patterning, are ancestral for winged insects. Testing this assumption requires comparisons of wing development in Drosophila and other winged insects. Here we review data that bear on this assumption, including new data on the functions of wingless and decapentaplegic during appendage allocation in the red flour beetle Tribolium castaneum.
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Affiliation(s)
- E L Jockusch
- Department of Ecology and Evolutionary Biology, 75 N. Eagleville Rd., U-3043, University of Connecticut, Storrs, CT 06269, USA.
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21
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Miyawaki K, Mito T, Sarashina I, Zhang H, Shinmyo Y, Ohuchi H, Noji S. Involvement of Wingless/Armadillo signaling in the posterior sequential segmentation in the cricket, Gryllus bimaculatus (Orthoptera), as revealed by RNAi analysis. Mech Dev 2004; 121:119-30. [PMID: 15037314 DOI: 10.1016/j.mod.2004.01.002] [Citation(s) in RCA: 128] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2003] [Revised: 01/05/2004] [Accepted: 01/09/2004] [Indexed: 10/26/2022]
Abstract
In insects, there are two different modes of segmentation. In the higher dipteran insects (like Drosophila), their segmentation takes place almost simultaneously in the syncytial blastoderm. By contrast, in the orthopteran insects (like Schistocerca (grasshopper)), the anterior segments form almost simultaneously in the cellular blastoderm and then the remaining posterior part elongates to form segments sequentially from the posterior proliferative zone. Although most of their orthologues of the Drosophila segmentation genes may be involved in their segmentation, little is known about their roles. We have investigated segmentation processes of Gryllus bimaculatus, focusing on its orthologues of the Drosophila segment-polarity genes, G. bimaculatus wingless (Gbwg), armadillo (Gbarm) and hedgehog (Gbhh). Gbhh and Gbwg were observed to be expressed in the each anterior segment and the posterior proliferative zone. In order to know their roles, we used RNA interference (RNAi). We could not observed any significant effects of RNAi for Gbwg and Gbhh on segmentation, probably due to functional replacement by another member of the corresponding gene families. Embryos obtained by RNAi for Gbarm exhibited abnormal anterior segments and lack of the abdomen. Our results suggest that GbWg/GbArm signaling is involved in the posterior sequential segmentation in the G. bimaculatus embryos, while Gbwg, Gbarm and Gbhh are likely to act as the segment-polarity genes in the anterior segmentation similarly as in Drosophila.
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Affiliation(s)
- Katsuyuki Miyawaki
- Department of Biological Science and Technology, Faculty of Engineering, The University of Tokushima, 2-1 Minami-jyosanjima-cho, Tokushima 770-8506, Japan
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22
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Kuo DH, Shankland M. A distinct patterning mechanism of O and P cell fates in the development of the rostral segments of the leech Helobdella robusta: implications for the evolutionary dissociation of developmental pathway and morphological outcome. Development 2004; 131:105-15. [PMID: 14645128 DOI: 10.1242/dev.00919] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Despite a high degree of homonomy in the segmental organization of the ectoderm, the body plan of the leech is divided into two zones based on the distinct cell lineage patterns that give rise to the O/P portion of the segmental ectoderm. In the midbody and caudal segments, each segmental repeat of ectoderm arises in part from one o' blast cell and one `p' blast cell. These two blast cells are positionally specified to distinct O and P fates,and give rise to differentiated descendant cells called O and P pattern elements, respectively. In the rostral segments, each segmental repeat of O and P pattern elements arises from a single `op' blast cell. Based on their developmental fates and their responses to the ablation of neighboring cells,the granddaughters of the primary op blast cell are categorized into two O-type cells and two P-type cells. The O-type cells do not require the presence of the rest of the op blast cell clone for their normal development. By contrast, normal development of the P-type cells depends upon interactions with the other OP sublineages. Additional experiments showed that the O-type cells are the source of a repressive signal involved in the normal fate specification of the P-type cells. Our data suggest that the cell interactions involved in fate specification differ substantially in the rostral and midbody segments, even though the set of differentiated descendants produced by the rostral OP pathway and the midbody O and P pathways are very similar.
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Affiliation(s)
- Dian-Han Kuo
- Graduate Program in Zoology and Section of Molecular Cell and Developmental Biology, Institute of Cellular and Molecular Biology, University of Texas at Austin, Austin, Texas 78712, USA.
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23
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Possible developmental mechanisms underlying the origin of the crown lineages of arthropods. ACTA ACUST UNITED AC 2004. [DOI: 10.1007/bf02901742] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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24
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Urbach R, Technau GM. Segment polarity and DV patterning gene expression reveals segmental organization of the Drosophila brain. Development 2003; 130:3607-20. [PMID: 12835379 DOI: 10.1242/dev.00532] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The insect brain is traditionally subdivided into the trito-, deuto- and protocerebrum. However, both the neuromeric status and the course of the borders between these regions are unclear. The Drosophila embryonic brain develops from the procephalic neurogenic region of the ectoderm, which gives rise to a bilaterally symmetrical array of about 100 neuronal precursor cells, called neuroblasts. Based on a detailed description of the spatiotemporal development of the entire population of embryonic brain neuroblasts, we carried out a comprehensive analysis of the expression of segment polarity genes (engrailed, wingless, hedgehog, gooseberry distal, mirror) and DV patterning genes (muscle segment homeobox, intermediate neuroblast defective, ventral nervous system defective) in the procephalic neuroectoderm and the neuroblast layer (until stage 11, when all neuroblasts are formed). The data provide new insight into the segmental organization of the procephalic neuroectodem and evolving brain. The expression patterns allow the drawing of clear demarcations between trito-, deuto- and protocerebrum at the level of identified neuroblasts. Furthermore, we provide evidence indicating that the protocerebrum (most anterior part of the brain) is composed of two neuromeres that belong to the ocular and labral segment, respectively. These protocerebral neuromeres are much more derived compared with the trito- and deutocerebrum. The labral neuromere is confined to the posterior segmental compartment. Finally, similarities in the expression of DV patterning genes between the Drosophila and vertebrate brains are discussed.
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Affiliation(s)
- Rolf Urbach
- Institut für Genetik, Universität Mainz, D-55099 Mainz, Germany
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25
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Abstract
Hedgehog proteins are secreted molecules that bind to their cell surface receptors to elicit concentration dependent responses essential for numerous tissue patterning and cell differentiation events during embryogenesis. However, during early stages of pancreas organogenesis, hedgehog signaling has been shown to inhibit tissue morphogenesis and cell differentiation. By contrast, recent cell culture studies indicate that an active hedgehog pathway might be required for maintenance of adult endocrine cell functions. This review describes our current understanding of the requirement of hedgehog signaling during pancreas morphogenesis and cell differentiation and discusses how individual hedgehog genes might act at various stages to ensure proper pancreas development and organ function.
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Affiliation(s)
- Matthias Hebrok
- Diabetes Center, Department of Medicine, University of California, San Francisco, CA 94143-0540, USA.
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26
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Lee JD, Amanai K, Shearn A, Treisman JE. The ubiquitin ligase Hyperplastic discs negatively regulates hedgehog and decapentaplegic expression by independent mechanisms. Development 2002; 129:5697-706. [PMID: 12421709 DOI: 10.1242/dev.00159] [Citation(s) in RCA: 154] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Photoreceptor differentiation in the Drosophila eye disc progresses from posterior to anterior in a wave driven by the Hedgehog and Decapentaplegic signals. Cells mutant for the hyperplastic discs gene misexpress both of these signaling molecules in anterior regions of the disc, leading to premature photoreceptor differentiation and overgrowth of surrounding tissue. The two genes are independently regulated by hyperplastic discs; decapentaplegic can still be misexpressed in cells mutant for both hyperplastic discs and hedgehog, and a repressor form of the transcription factor Cubitus interruptus can block decapentaplegic misexpression but not hedgehog misexpression. Loss of hyperplastic discs causes the accumulation of full-length Cubitus interruptus protein, but not of Smoothened, in both the eye and wing discs. hyperplastic discs encodes a HECT domain E3 ubiquitin ligase that is likely to act by targeting Cubitus interruptus and an unknown activator of hedgehog expression for proteolysis.
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Affiliation(s)
- Jeffrey D Lee
- Skirball Institute of Biomolecular Medicine and Department of Cell Biology, NYU School of Medicine, 540 First Avenue, New York, NY 10016, USA
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27
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Von Dassow G, Odell GM. Design and constraints of the Drosophila segment polarity module: robust spatial patterning emerges from intertwined cell state switches. THE JOURNAL OF EXPERIMENTAL ZOOLOGY 2002; 294:179-215. [PMID: 12362429 DOI: 10.1002/jez.10144] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The Drosophila segment polarity genes constitute the last tier in the segmentation cascade; their job is to maintain the boundaries between parasegments and provide positional "read-outs" within each parasegment for the entire developmental history of the animal. These genes constitute a relatively well-defined network with a relatively well-understood patterning task. In a previous publication (von Dassow et al. 2000. Nature 406:188-192) we showed that a computer model predicts the segment polarity network to be a robust boundary-making device. Here we elaborate those findings. First, we explore the constraints among parameters that govern the network model. Second, we test architectural variants of the core network, and show that the network tolerates a wide variety of adjustments in design. Third, we evaluate several topologically identical models that incorporate more or less molecular detail, finding that more-complex models perform noticeably better than simplified ones. Fourth, we discuss two instances in which the failure of the network model to behave in a life-like fashion highlights mechanistic details that need further experimental investigation. We conclude with an explanation of how the segment polarity network can be understood as an interwoven conspiracy of simple dynamical elements, several bistable switches and a homeostat. The robustness with which the network as a whole maintains a spatial regime of stable cell state emerges from generic dynamical properties of these simple elements.
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Affiliation(s)
- George Von Dassow
- Department of Zoology, University of Washington, Seattle, Washington 98105, USA.
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28
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Suzuki T, Saigo K. Transcriptional regulation of atonal required for Drosophila larval eye development by concerted action of eyes absent, sine oculis and hedgehog signaling independent of fused kinase and cubitus interruptus. Development 2000; 127:1531-40. [PMID: 10704398 DOI: 10.1242/dev.127.7.1531] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Bolwig's organ is the larval light-sensing system consisting of 12 photoreceptors and its development requires atonal activity. Here, we showed that Bolwig's organ formation and atonal expression are controlled by the concerted function of hedgehog, eyes absent and sine oculis. Bolwig's organ primordium was first detected as a cluster of about 14 Atonal-positive cells at the posterior edge of the ocular segment in embryos and hence, atonal expression may define the region from which a few Atonal-positive founder cells (future primary photoreceptor cells) are generated by lateral specification. In Bolwig's organ development, neural differentiation precedes photoreceptor specification, since Elav, a neuron-specific antigen, whose expression is under the control of atonal, is expressed in virtually all early-Atonal-positive cells prior to the establishment of founder cells. Neither Atonal expression nor Bolwig's organ formation occurred in the absence of hedgehog, eyes absent or sine oculis activity. Genetic and histochemical analyses indicated that (1) responsible Hedgehog signals derive from the ocular segment, (2) Eyes absent and Sine oculis act downstream of or in parallel with Hedgehog signaling and (3) the Hedgehog signaling pathway required for Bolwig's organ development is a new type and lacks Fused kinase and Cubitus interruptus as downstream components.
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Affiliation(s)
- T Suzuki
- Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
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29
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Seecoomar M, Agarwal S, Vani K, Yang G, Mohler J. knot is required for the hypopharyngeal lobe and its derivatives in the Drosophila embryo. Mech Dev 2000; 91:209-15. [PMID: 10704845 DOI: 10.1016/s0925-4773(99)00305-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The genetic control of segmentation in the Drosophila larval head has been only partially elucidated. We report that the knot (kn) gene of Drosophila is required for the formation of the hypopharyngeal lobe in the germ-band stage embryo and the ventral arms and lateralgräte of the larval head skeleton. Rearrangement mutations of knot disrupt the previously characterized gene, collier, which encodes a COE-family transcription factor. kn is required for the activation of cnc (cap'n'collar, a bZIP homeotic selector gene) in the progenitors of hypopharyngeal lobe. kn is also required for the activation of an EST marker for the cephalic mesoderm, CK01299. Based on the relative expression of kn and the posterior compartment-specific gene hedgehog, we provide additional evidence that in Drosophila, unlike many other insects, the hypopharyngeal lobe arises from part of the mandibular segment.
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Affiliation(s)
- M Seecoomar
- Department of Biological Sciences, Barnard College, 3009 Broadway, New York, NY 10027 USA
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30
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Crozatier M, Valle D, Dubois L, Ibnsouda S, Vincent A. Head versus trunk patterning in the Drosophila embryo; collier requirement for formation of the intercalary segment. Development 1999; 126:4385-94. [PMID: 10477305 DOI: 10.1242/dev.126.19.4385] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Whereas the segmental nature of the insect head is well established, relatively little is known about the genetic and molecular mechanisms governing this process. In this paper, we report the phenotypic analysis of mutations in collier (col), which encodes the Drosophila member of the COE family of HLH transcription factors and is activated at the blastoderm stage in a region overlapping a parasegment (PS0: posterior intercalary and anterior mandibular segments) and a mitotic domain, MD2. col mutant embryos specifically lack intercalary ectodermal structures. col activity is required for intercalary-segment expression both of the segment polarity genes hedgehog, engrailed, and wingless, and of the segment identity gene cap and collar. The parasegmental register of col activation is controlled by the combined activities of the head-gap genes buttonhead and empty spiracles and the pair-rule gene even skipped; it therefore integrates inputs from both the head and trunk segmentation systems, which were previously considered as being essentially independent. After gastrulation, positive autoregulation of col is limited to cells of anterior PS0. Conversely, heat-pulse induced ubiquitous expression of Col leads to disruption of the head skeleton. Together, these results indicate that col is required for establishment of the PS(−1)/PS0 parasegmental border and formation of the intercalary segment. Our data support neither a simple combinatorial model for segmental patterning of the head nor a direct activation of segment polarity gene expression by head-gap genes, but rather argue for the existence of parasegment-specific second order regulators acting in the head, at a level similar to that of pair-rule genes in the trunk.
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Affiliation(s)
- M Crozatier
- Centre de Biologie du Développement, UMR 5547, CNRS/Université Paul Sabatier, 31062 TOULOUSE 04 cedex, France
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31
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Affiliation(s)
- L V Goodrich
- Department of Developmental Biology, Howard Hughes Medical Institute, Stanford University School of Medicine, California 94305, USA
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32
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Hartmann B, Reichert H. The genetics of embryonic brain development in Drosophila. Mol Cell Neurosci 1998; 12:194-205. [PMID: 9828085 DOI: 10.1006/mcne.1998.0716] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
- B Hartmann
- Institute of Zoology, University of Basel, Basel, Rheinsprung 9, 4051, Switzerland
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33
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Gallitano-Mendel A, Finkelstein R. Ectopic orthodenticle expression alters segment polarity gene expression but not head segment identity in the Drosophila embryo. Dev Biol 1998; 199:125-37. [PMID: 9676197 DOI: 10.1006/dbio.1998.8917] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The cephalic gap genes specify anterior head development in the Drosophila embryo. However, the mechanisms of action of these genes remain poorly understood. Here, we focused on the cephalic gap gene orthodenticle (otd), which establishes a specific region of the anterior head. It has been proposed that otd acts in a combinatorial fashion with the cephalic gap genes empty spiracles (ems) and buttonhead (btd) to assign segmental identities in this region. To test this model, we used a heat-inducible transgene to generate pulses of ubiquitous otd expression during embryonic development. Ectopic otd expression caused significant defects in head formation, including the duplication of sensory structures derived from otd-dependent segments. However, these defects do not appear to result from the transformation of head segment identities predicted by the combinatorial model. Instead, they correlate with specific regulatory effects of otd on the expression of the segment polarity genes engrailed (en) and wingless (wg). Ectopic otd expression also caused the loss of head structures derived from the maxillary segment, which lies posterior to the otd domain. We show that this effect is associated with otd repression of the homeotic selector gene Deformed (Dfd).
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Affiliation(s)
- A Gallitano-Mendel
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia 19104-6074, USA
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