scholarly journals The genome of a daddy-long-legs (Opiliones) illuminates the evolution of arachnid appendages

2021 ◽  
Vol 288 (1956) ◽  
pp. 20211168
Author(s):  
Guilherme Gainett ◽  
Vanessa L. González ◽  
Jesús A. Ballesteros ◽  
Emily V. W. Setton ◽  
Caitlin M. Baker ◽  
...  
Keyword(s):  
Genetic Basis ◽  
Hox Genes ◽  
Genome Duplication ◽  
Draft Genome ◽  
Growth Factor Receptor ◽  
Loss Of Function ◽  
Sex Combs Reduced ◽  
Sex Combs ◽  
Dynamic Genome ◽  
Epidermal Growth

Chelicerate arthropods exhibit dynamic genome evolution, with ancient whole-genome duplication (WGD) events affecting several orders. Yet, genomes remain unavailable for a number of poorly studied orders, such as Opiliones (daddy-long-legs), which has hindered comparative study. We assembled the first harvestman draft genome for the species Phalangium opilio , which bears elongate, prehensile appendages, made possible by numerous distal articles called tarsomeres. Here, we show that the genome of P. opilio exhibits a single Hox cluster and no evidence of WGD. To investigate the developmental genetic basis for the quintessential trait of this group—the elongate legs—we interrogated the function of the Hox genes Deformed ( Dfd ) and Sex combs reduced ( Scr ), and a homologue of Epidermal growth factor receptor ( Egfr ). Knockdown of Dfd incurred homeotic transformation of two pairs of legs into pedipalps, with dramatic shortening of leg segments in the longest leg pair, whereas homeosis in L3 is only achieved upon double Dfd + Scr knockdown. Knockdown of Egfr incurred shortened appendages and the loss of tarsomeres. The similarity of Egfr loss-of-function phenotypic spectra in insects and this arachnid suggest that repeated cooption of EGFR signalling underlies the independent gains of supernumerary tarsomeres across the arthropod tree of life.

scholarly journals The genome of a daddy-long-legs (Opiliones) illuminates the evolution of arachnid appendages and chelicerate genome architecture

2021 ◽  
Author(s):  
Guilherme Gainett ◽  
Vanessa L. González ◽  
Jesús A. Ballesteros ◽  
Emily V. W. Setton ◽  
Caitlin M. Baker ◽  
...  
Keyword(s):  
Whole Genome Duplication ◽  
Hox Genes ◽  
Genome Duplication ◽  
Draft Genome ◽  
Growth Factor Receptor ◽  
Single Copy ◽  
Developmental Genetics ◽  
Genome Architecture ◽  
Whole Genome ◽  
Duplication Events

AbstractChelicerates exhibit dynamic evolution of genome architecture, with multiple whole genome duplication events affecting groups like spiders, scorpions, and horseshoe crabs. Yet, genomes remain unavailable for several chelicerate orders, such as Opiliones (harvestmen), which has hindered comparative genomics and developmental genetics across arachnids. We assembled a draft genome of the daddy-long-legs Phalangium opilio, which revealed no signal of whole genome duplication. To test the hypothesis that single-copy Hox genes of the harvestman exhibit broader functions than subfunctionalized spider paralogs, we performed RNA interference against Deformed in P. opilio. Knockdown of Deformed incurred homeotic transformation of the two anterior pairs of walking legs into pedipalpal identity; by comparison, knockdown of the spatially restricted paralog Deformed-A in the spider affects only the first walking leg. To investigate the genetic basis for leg elongation and tarsomere patterning, we identified and interrogated the function of an Epidermal growth factor receptor (Egfr) homolog. Knockdown of Egfr incurred shortened appendages and the loss of distal leg structures. The overlapping phenotypic spectra of Egfr knockdown experiments in the harvestman and multiple insect models are striking because tarsomeres have evolved independently in these groups. Our results suggest a conserved role for Egfr in patterning distal leg structures across arthropods, as well as cooption of EGFR signaling in tarsomere patterning in both insects and arachnids. The establishment of genomic resources for P. opilio, together with functional investigations of appendage fate specification and distal patterning mechanisms, are key steps in understanding how daddy-long-legs make their long legs.

Sequence of the Tribolium castaneum Homeotic Complex: The Region Corresponding to the Drosophila melanogaster Antennapedia Complex

Genetics ◽  
2002 ◽  
Vol 160 (3) ◽  
pp. 1067-1074
Author(s):  
Susan J Brown ◽  
John P Fellers ◽  
Teresa D Shippy ◽  
Elizabeth A Richardson ◽  
Mark Maxwell ◽  
...  
Keyword(s):  
Tribolium Castaneum ◽  
Hox Genes ◽  
Transcription Unit ◽  
Sex Combs Reduced ◽  
Sex Combs ◽  
Selector Genes ◽  
Homeotic Selector Genes ◽  
Encoding Genes ◽  
Single Cluster ◽  
Homeotic Selector

Abstract The homeotic selector genes of the red flour beetle, Tribolium castaneum, are located in a single cluster. We have sequenced the region containing the homeotic selector genes required for proper development of the head and anterior thorax, which is the counterpart of the ANTC in Drosophila. This 280-kb interval contains eight homeodomain-encoding genes, including single orthologs of the Drosophila genes labial, proboscipedia, Deformed, Sex combs reduced, fushi tarazu, and Antennapedia, as well as two orthologs of zerknüllt. These genes are all oriented in the same direction, as are the Hox genes of amphioxus, mice, and humans. Although each transcription unit is similar to its Drosophila counterpart in size, the Tribolium genes contain fewer introns (with the exception of the two zerknüllt genes), produce shorter mRNAs, and encode smaller proteins. Unlike the ANTC, this region of the Tribolium HOMC contains no additional genes.

scholarly journals A point mutation in the extracellular domain activates LET-23, the Caenorhabditis elegans epidermal growth factor receptor homolog.

1996 ◽  
Vol 16 (2) ◽  
pp. 529-537 ◽  
Author(s):  
W S Katz ◽  
G M Lesa ◽  
D Yannoukakos ◽  
T R Clandinin ◽  
J Schlessinger ◽  
...  
Keyword(s):  
Epidermal Growth Factor Receptor ◽  
Caenorhabditis Elegans ◽  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Point Mutation ◽  
Growth Factor Receptor ◽  
Extracellular Domain ◽  
Cysteine Residue ◽  
Loss Of Function ◽  
Epidermal Growth

The let-23 gene encodes a Caenorhabditis elegans homolog of the epidermal growth factor receptor (EGFR) necessary for vulval development. We have characterized a mutation of let-23 that activates the receptor and downstream signal transduction, leading to excess vulval differentiation. This mutation alters a conserved cysteine residue in the extracellular domain and is the first such point mutation in the EGFR subfamily of tyrosine kinases. Mutation of a different cysteine in the same subdomain causes a strong loss-of-function phenotype, suggesting that cysteines in this region are important for function and nonequivalent. Vulval precursor cells can generate either of two subsets of vulval cells (distinct fates) in response to sa62 activity. The fates produced depended on the copy number of the mutation, suggesting that quantitative differences in receptor activity influence the decision between these two fates.

The Drosophila kismet gene is related to chromatin-remodeling factors and is required for both segmentation and segment identity

Development ◽  
1999 ◽  
Vol 126 (6) ◽  
pp. 1175-1187 ◽  
Author(s):  
G. Daubresse ◽  
R. Deuring ◽  
L. Moore ◽  
O. Papoulas ◽  
I. Zakrajsek ◽  
...  
Keyword(s):  
Chromatin Remodeling ◽  
Homeotic Genes ◽  
Loss Of Function ◽  
Larval Body ◽  
Sex Combs Reduced ◽  
Trithorax Group ◽  
Sex Combs ◽  
Pair Rule Gene ◽  
Body Segmentation ◽  
Group Protein

The Drosophila kismet gene was identified in a screen for dominant suppressors of Polycomb, a repressor of homeotic genes. Here we show that kismet mutations suppress the Polycomb mutant phenotype by blocking the ectopic transcription of homeotic genes. Loss of zygotic kismet function causes homeotic transformations similar to those associated with loss-of-function mutations in the homeotic genes Sex combs reduced and Abdominal-B. kismet is also required for proper larval body segmentation. Loss of maternal kismet function causes segmentation defects similar to those caused by mutations in the pair-rule gene even-skipped. The kismet gene encodes several large nuclear proteins that are ubiquitously expressed along the anterior-posterior axis. The Kismet proteins contain a domain conserved in the trithorax group protein Brahma and related chromatin-remodeling factors, providing further evidence that alterations in chromatin structure are required to maintain the spatially restricted patterns of homeotic gene transcription.

Analysis of Drosophila proboscipedia mutant alleles

Genome ◽  
2004 ◽  
Vol 47 (3) ◽  
pp. 600-609 ◽  
Author(s):  
I Tayyab ◽  
H M Hallahan ◽  
A Percival-Smith
Keyword(s):  
Dna Sequence ◽  
Hox Genes ◽  
Genetic Interaction ◽  
Direct Interaction ◽  
Protein Product ◽  
Maxillary Palp ◽  
Phenotypic Analysis ◽  
Sex Combs Reduced ◽  
Important Region ◽  
Sex Combs

Proboscipedia (PB) is a HOX protein required for adult maxillary palp and proboscis formation. To identify domains of PB important for function, 21 pb point mutant alleles were sequenced. Twelve pb alleles had DNA sequence changes that encode an altered PB protein product. The DNA sequence changes of these 12 alleles fell into 2 categories: missense alleles that effect the PB homeodomain (HD), and nonsense or frameshift alleles that result in C-terminal truncations of the PB protein. The phenotypic analysis of the pb homeobox missense alleles suggests that the PB HD is required for maxillary palp and proboscis development and pb – Sex combs reduced (Scr) genetic interaction. The phenotypic analysis of the pb nonsense or frameshift alleles suggests that the C-terminus is an important region required for maxillary palp and proboscis development and pb–Scr genetic interaction. PB and SCR do not interact directly with one another in a co-immunoprecipitation assay and in a yeast two-hybrid analysis, which suggests the pb–Scr genetic interaction is not mediated by a direct interaction between PB and SCR.Key words: proboscipedia, Sex combs reduced, Hox genes, mutant analysis, Drosophila body plan, appendage development.

scholarly journals Hox genes mediate the escalation of sexually antagonistic traits in water striders

2019 ◽  
Vol 15 (2) ◽  
pp. 20180720 ◽  
Author(s):  
Antonin Jean Johan Crumière ◽  
Abderrahman Khila
Keyword(s):  
Sexual Conflict ◽  
Hox Genes ◽  
Complete Loss ◽  
Water Strider ◽  
Fitness Costs ◽  
Sex Combs Reduced ◽  
Hox Gene ◽  
Water Striders ◽  
Sex Combs ◽  
Sex Comb

Sexual conflict occurs when traits favoured in one sex impose fitness costs on the other sex. In the case of sexual conflict over mating rate, the sexes often undergo antagonistic coevolution and escalation of traits that enhance females' resistance to superfluous mating and traits that increase males' persistence. How this escalation in sexually antagonistic traits is established during ontogeny remains unclear. In the water strider Rhagovelia antilleana, male persistence traits consist of sex combs on the forelegs and multiple rows of spines and a thick femur in the rear legs. Female resistance traits consist of a prominent spike-like projection of the pronotum. RNAi knockdown against the Hox gene Sex Combs Reduced resulted in the reduction in both the sex comb in males and the pronotum projection in females. RNAi against the Hox gene Ultrabithorax resulted in the complete loss or reduction of all persistence traits in male rear legs. These results demonstrate that Hox genes can be involved in intra- and inter-locus sexual conflict and mediate escalation of sexually antagonistic traits.

scholarly journals Loss-of-function Additional sex combs like 1 mutations disrupt hematopoiesis but do not cause severe myelodysplasia or leukemia

Blood ◽  
2010 ◽  
Vol 115 (1) ◽  
pp. 38-46 ◽  
Author(s):  
Cynthia L. Fisher ◽  
Nicolas Pineault ◽  
Christy Brookes ◽  
Cheryl D. Helgason ◽  
Hideaki Ohta ◽  
...  
Keyword(s):  
Hox Genes ◽  
Homeodomain Protein ◽  
Loss Of Function ◽  
Genomic Amplification ◽  
Interaction Domain ◽  
Hematopoietic Stem ◽  
Amino Terminal ◽  
Sex Combs ◽  
Additional Sex Combs ◽  
Cell Fractions

Abstract The Additional sex combs like 1 (Asxl1) gene is 1 of 3 mammalian homologs of the Additional sex combs (Asx) gene of Drosophila. Asx is unusual because it is required to maintain both activation and silencing of Hox genes in flies and mice. Asxl proteins are characterized by an amino terminal homology domain, by interaction domains for nuclear receptors, and by a C-terminal plant homeodomain protein-protein interaction domain. A recent study of patients with myelodysplastic syndrome (MDS) and chronic myelomonocytic leukemia (CMML) revealed a high incidence of truncation mutations that would delete the PHD domain of ASXL1. Here, we show that Asxl1 is expressed in all hematopoietic cell fractions analyzed. Asxl1 knockout mice exhibit defects in frequency of differentiation of lymphoid and myeloid progenitors, but not in multipotent progenitors. We do not detect effects on hematopoietic stem cells, or in peripheral blood. Notably, we do not detect severe myelodysplastic phenotypes or leukemia in this loss-of-function model. We conclude that Asxl1 is needed for normal hematopoiesis. The mild phenotypes observed may be because other Asxl genes have redundant function with Asxl1, or alternatively, MDS or oncogenic phenotypes may result from gain-of-function Asxl mutations caused by genomic amplification, gene fusion, or truncation of Asxl1.

scholarly journals Hox genes limit germ cell formation in the short germ insect Gryllus bimaculatus

2018 ◽  
Author(s):  
Austen A. Barnett ◽  
Taro Nakamura ◽  
Cassandra G. Extavour
Keyword(s):  
Hox Genes ◽  
Primordial Germ Cells ◽  
Cell Formation ◽  
Gryllus Bimaculatus ◽  
Sex Combs Reduced ◽  
Body Regions ◽  
Sex Combs ◽  
Hemimetabolous Insect ◽  
Encoding Genes ◽  
Germ Cell Formation

AbstractHox genes are conserved transcription factor-encoding genes that specify the identity of body regions in bilaterally symmetrical animals. In the cricket Gryllus bimaculatus, a member of the hemimetabolous insect group Orthoptera, the induction of a subset of mesodermal cells to form the primordial germ cells (PGCs) is restricted to the second through the fourth abdominal segments (A2-A4). In numerous insect species, the Hox genes Sex-combs reduced (Scr), Antennapedia (Antp), Ultrabithorax (Ubx) and abdominal-A (abd-A) jointly regulate the identities of middle and posterior body segments, suggesting that these genes may restrict PGC formation to specific abdominal segments in G. bimaculatus. Here we show that all of these Hox genes, either individually or in segment-specific combinations, restrict PGC formation. Our data provides evidence for a segmental Hox code used to regulate the placement of PGC formation, reminiscent of the segmental Hox codes used in other arthropod groups to establish other aspects of segmental identity. These data also provide, to our knowledge, the first evidence for this ancient group of genes in determining PGC placement within the context of axial patterning in any animal studied thus far.

TheDrosophilaproboscis is specified by two Hox genes,proboscipediaandSex combs reduced, via repression of leg and antennal appendage genes

Development ◽  
2001 ◽  
Vol 128 (14) ◽  
pp. 2803-2814 ◽  
Author(s):  
Arhat Abzhanov ◽  
Stacy Holtzman ◽  
Thomas C. Kaufman
Keyword(s):  
Limb Development ◽  
Hox Genes ◽  
Distinct Type ◽  
Wild Type ◽  
Fate Map ◽  
Genetic Studies ◽  
Unique Type ◽  
Sex Combs Reduced ◽  
Sex Combs ◽  
Labial Disc

The proboscis is one of the most highly modified appendages in Drosophila melanogaster. However, the phenotypes of proboscipedia (pb) mutants, which transform the proboscis into leg or antenna, indicate a basic homology among these limbs. Recent genetic studies have revealed a developmental system for patterning appendages and identified several genes required for limb development. Among these are: extradenticle (exd), homothorax (hth), dachshund (dac), Distal-less (Dll) and spalt (sal). These limb genes have not been well studied in wild-type mouthparts and their role if any in this appendage is not well understood. Here we demonstrate that the homeotic gene products Proboscipedia (Pb) and Sex combs reduced (Scr) regulate the limb genes in the labial disc to give rise to a unique type of appendage, the proboscis. Pb inhibits exd, dac and sal expression and downregulates Dll. This observation explains the ability of Pb to inhibit the effects of ectopically expressed trunk Hox genes in the proboscis, to suppress leg identity in the trunk and to transform antenna to maxillary palp. Scr suppresses sal expression and also downregulates Dll in the labial discs; discs mutant for both pb and Scr give rise to complete antennae, further demonstrating appendage homology. In the labial disc, Pb positively regulates transcription of Scr, whereas in the embryo, Scr positively regulates pb. Additionally, our results suggests a revised fate map of the labial disc. We conclude that the proboscis constitutes a genetically distinct type of appendage whose morphogenesis does not require several important components of leg and/or antennal patterning systems, but retains distal segmental homology with these appendages.

scholarly journals Hox genes limit germ cell formation in the short germ insect Gryllus bimaculatus

2019 ◽  
Vol 116 (33) ◽  
pp. 16430-16435
Author(s):  
Austen A. Barnett ◽  
Taro Nakamura ◽  
Cassandra G. Extavour
Keyword(s):  
Hox Genes ◽  
Primordial Germ Cells ◽  
Cell Formation ◽  
Gryllus Bimaculatus ◽  
Sex Combs Reduced ◽  
Body Regions ◽  
Sex Combs ◽  
Hemimetabolous Insect ◽  
Encoding Genes

Hox genes are conserved transcription factor-encoding genes that specify the identity of body regions in bilaterally symmetrical animals. In the cricket Gryllus bimaculatus, a member of the hemimetabolous insect group Orthoptera, the induction of a subset of mesodermal cells to form the primordial germ cells (PGCs) is restricted to the second through the fourth abdominal segments (A2 to A4). In numerous insect species, the Hox genes Sex-combs reduced (Scr), Antennapedia (Antp), Ultrabithorax (Ubx), and abdominal-A (abd-A) jointly regulate the identities of middle and posterior body segments, suggesting that these genes may restrict PGC formation to specific abdominal segments in G. bimaculatus. Here we show that reducing transcript levels of some or all of these Hox genes results in supernumerary and/or ectopic PGCs, either individually or in segment-specific combinations, suggesting that the role of these Hox genes is to limit PGC development with respect to their number, segmental location, or both. These data provide evidence of a role for this ancient group of genes in PGC development.

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