The Experts below are selected from a list of 1278 Experts worldwide ranked by ideXlab platform
Georg Mayer - One of the best experts on this subject based on the ideXlab platform.
-
File F1 from Halloween genes in panarthropods and the evolution of the early moulting pathway in Ecdysozoa
2018Co-Authors: Isabell Schumann, Lars Hering, Nathan Kenny, Jerome Hui, Georg MayerAbstract:List of species names and genes with NCBI or UniProt accession number used for phylogenetic analyses of neverland, Halloween genes, nuclear receptor genes, Early genes, and CYP18A1. Identified sequences of Euperipatoides rowelli (Onychophora) and Hypsibius exemplaris (Tardigrada) are included on table 7 and 8, respectively
-
Conserved versus derived patterns of controlled cell death during the embryonic development of two species of Onychophora (velvet worms).
Developmental dynamics : an official publication of the American Association of Anatomists, 2017Co-Authors: Sandra Treffkorn, Georg MayerAbstract:Background Apoptosis is involved in various developmental processes, including cell migration and tissue and organ formation. Some of these processes are conserved across metazoans, while others are specific to particular taxa. Although the patterns of apoptosis have been investigated in arthropods, no corresponding data are available from one of their closest relatives, the Onychophora (velvet worms). Results We analyzed the patterns of apoptosis in embryos of two Onychophoran species: the lecithotrophic/matrotrophic viviparous peripatopsid Euperipatoides rowelli, and the placentotrophic viviparous peripatid Principapillatus hitoyensis. Our data show that apoptosis occurs early in development and might be responsible for the degeneration of extra-embryonic tissues. Moreover, apoptosis might be involved in the morphogenesis of the ventral and preventral organs in both species and occurs additionally in the placental stalk of P. hitoyensis. Conclusions Despite the different developmental modes in these Onychophoran species, our data suggest that patterns of apoptosis are conserved among Onychophorans. While apoptosis in the dorsal extra-embryonic tissue might contribute to dorsal closure-a process also known from arthropods-the involvement of apoptosis in ventral closure might be unique to Onychophorans. Apoptosis in the placental stalk of P. hitoyensis is most likely a derived feature of the placentotrophic Onychophorans. Developmental Dynamics 246:403-416, 2017. © 2017 Wiley Periodicals, Inc.
-
Assessing segmental versus non-segmental features in the ventral nervous system of Onychophorans (velvet worms)
BMC Evolutionary Biology, 2017Co-Authors: Christine Martin, Vladimir Gross, Paul A. Stevenson, Hans Joachim Pflüger, Georg MayerAbstract:Background Due to their phylogenetic position as one of the closest arthropod relatives, studies of the organisation of the nervous system in Onychophorans play a key role for understanding the evolution of body segmentation in arthropods. Previous studies revealed that, in contrast to the arthropods, segmentally repeated ganglia are not present within the Onychophoran ventral nerve cords, suggesting that segmentation is either reduced or might be incomplete in the Onychophoran ventral nervous system. Results To assess segmental versus non-segmental features in the ventral nervous system of Onychophorans, we screened the nerve cords for various markers, including synapsin, serotonin, gamma-aminobutyric acid, RFamide, dopamine, tyramine and octopamine. In addition, we performed retrograde fills of serially repeated commissures and leg nerves to localise the position of neuronal somata supplying those. Our data revealed a mixture of segmental and non-segmental elements within the Onychophoran nervous system. Conclusions We suggest that the segmental ganglia of arthropods evolved by a gradual condensation of subsets of neurons either in the arthropod or the arthropod-tardigrade lineage. These findings are in line with the hypothesis of gradual evolution of segmentation in panarthropods and thus contradict a loss of ancestral segmentation within the Onychophoran lineage.
-
Additional file 1: Figure S1. of Assessing segmental versus non-segmental features in the ventral nervous system of Onychophorans (velvet worms)
2017Co-Authors: Christine Martin, Vladimir Gross, Hans-joachim PflĂźger, Paul Stevenson, Georg MayerAbstract:Light micrographs of cross sections, stained with a DNA-selective marker, to visualise differential circumferences of the nerve cord within the interpedal and the leg-bearing regions in Onychophora. (PDF 114 kb
-
ORIGINAL ARTICLE Support for vicariant origins of the
2016Co-Authors: Savel R. Daniels, Universität Kassel, See Profile, Jacqueline Beggs, Thomas R Buckley, New Zealand Onychophora, Julia Allwood, Dianne Gleeson, Georg MayerAbstract:Aim The distribution of Onychophora across the southern continents has long been considered the result of vicariance events. However, it has recently been hypothesized that New Zealand was completely inundated during the late Oligocene (25–22 Ma) and therefore that the entire biota is the result of long-distance dispersal. We tested this assumption using phylogenetic and molecular dating of DNA sequence data from Onychophora
Ralf Janssen - One of the best experts on this subject based on the ideXlab platform.
-
Analysis of the Wnt gene repertoire in an Onychophoran provides new insights into the evolution of segmentation
EvoDevo, 2014Co-Authors: Mattias Hogvall, Nico Posnien, Anna Schönauer, Graham E Budd, Alistair P Mcgregor, Ralf JanssenAbstract:Background The Onychophora are a probable sister group to Arthropoda, one of the most intensively studied animal phyla from a developmental perspective. Pioneering work on the fruit fly Drosophila melanogaster and subsequent investigation of other arthropods has revealed important roles for Wnt genes during many developmental processes in these animals. Results We screened the embryonic transcriptome of the Onychophoran Euperipatoides kanangrensis and found that at least 11 Wnt genes are expressed during embryogenesis. These genes represent 11 of the 13 known subfamilies of Wnt genes. Conclusions Many Onychophoran Wnt genes are expressed in segment polarity gene-like patterns, suggesting a general role for these ligands during segment regionalization, as has been described in arthropods. During early stages of development, Wnt2 , Wnt4 , and Wnt5 are expressed in broad multiple segment-wide domains that are reminiscent of arthropod gap and Hox gene expression patterns, which suggests an early instructive role for Wnt genes during E. kanangrensis segmentation.
-
Analysis of the Wnt gene repertoire in an Onychophoran provides new insights into the evolution of segmentation
EvoDevo, 2014Co-Authors: Mattias Hogvall, Nico Posnien, Anna Schönauer, Graham E Budd, Alistair P Mcgregor, Ralf JanssenAbstract:Background The Onychophora are a probable sister group to Arthropoda, one of the most intensively studied animal phyla from a developmental perspective. Pioneering work on the fruit fly Drosophila melanogaster and subsequent investigation of other arthropods has revealed important roles for Wnt genes during many developmental processes in these animals. Results We screened the embryonic transcriptome of the Onychophoran Euperipatoides kanangrensis and found that at least 11 Wnt genes are expressed during embryogenesis. These genes represent 11 of the 13 known subfamilies of Wnt genes. Conclusions Many Onychophoran Wnt genes are expressed in segment polarity gene-like patterns, suggesting a general role for these ligands during segment regionalization, as has been described in arthropods. During early stages of development, Wnt2 , Wnt4 , and Wnt5 are expressed in broad multiple segment-wide domains that are reminiscent of arthropod gap and Hox gene expression patterns, which suggests an early instructive role for Wnt genes during E. kanangrensis segmentation.
-
deciphering the Onychophoran segmentation gene cascade gene expression reveals limited involvement of pair rule gene orthologs in segmentation but a highly conserved segment polarity gene network
Developmental Biology, 2013Co-Authors: Ralf Janssen, Graham E BuddAbstract:The hallmark of the arthropods is their segmented body, although origin of segmentation, however, is unresolved. In order to shed light on the origin of segmentation we investigated orthologs of pair rule genes (PRGs) and segment polarity genes (SPGs) in a member of the closest related sister-group to the arthropods, the Onychophorans. Our gene expression data analysis suggests that most of the Onychophoran PRGs do not play a role in segmentation. One possible exception is the even-skipped (eve) gene that is expressed in the posterior end of the Onychophoran where new segments are likely patterned, and is also expressed in segmentation-gene typical transverse stripes in at least a number of newly formed segments. Other Onychophoran PRGs such as runt (run), hairy/Hes (h/Hes) and odd-skipped (odd) do not appear to have a function in segmentation at all. Onychophoran PRGs that act low in the segmentation gene cascade in insects, however, are potentially involved in segment-patterning. Most obvious is that from the expression of the pairberry (pby) gene ortholog that is expressed in a typical SPG-pattern. Since this result suggested possible conservation of the SPG-network we further investigated SPGs (and associated factors) such as Notum in the Onychophoran. We find that the expression patterns of SPGs in arthropods and the Onychophoran are highly conserved, suggesting a conserved SPG-network in these two clades, and indeed also in an annelid. This may suggest that the common ancestor of lophotrochozoans and ecdysozoans was already segmented utilising the same SPG-network, or that the SPG-network was recruited independently in annelids and Onychophorans/arthropods.
-
Gene expression suggests conserved aspects of Hox gene regulation in arthropods and provides additional support for monophyletic Myriapoda
EvoDevo, 2010Co-Authors: Ralf Janssen, Graham E BuddAbstract:Antisense transcripts of Ultrabithorax (aUbx) in the millipede Glomeris and the centipede Lithobius are expressed in patterns complementary to that of the Ubx sense transcripts. A similar complementary expression pattern has been described for non-coding RNAs (ncRNAs) of the bithoraxoid (bxd) locus in Drosophila, in which the transcription of bxd ncRNAs represses Ubx via transcriptional interference. We discuss our findings in the context of possibly conserved mechanisms of Ubx regulation in myriapods and the fly. Bicistronic transcription of Ubx and Antennapedia (Antp) has been reported previously for a myriapod and a number of crustaceans. In this paper, we show that Ubx/Antp bicistronic transcripts also occur in Glomeris and an Onychophoran, suggesting further conserved mechanisms of Hox gene regulation in arthropods. Myriapod monophyly is supported by the expression of aUbx in all investigated myriapods, whereas in other arthropod classes, including the Onychophora, aUbx is not expressed. Of the two splice variants of Ubx/Antp only one could be isolated from myriapods, representing a possible further synapomorphy of the Myriapoda.
Paul A. Stevenson - One of the best experts on this subject based on the ideXlab platform.
-
Assessing segmental versus non-segmental features in the ventral nervous system of Onychophorans (velvet worms)
BMC Evolutionary Biology, 2017Co-Authors: Christine Martin, Vladimir Gross, Paul A. Stevenson, Hans Joachim Pflüger, Georg MayerAbstract:Background Due to their phylogenetic position as one of the closest arthropod relatives, studies of the organisation of the nervous system in Onychophorans play a key role for understanding the evolution of body segmentation in arthropods. Previous studies revealed that, in contrast to the arthropods, segmentally repeated ganglia are not present within the Onychophoran ventral nerve cords, suggesting that segmentation is either reduced or might be incomplete in the Onychophoran ventral nervous system. Results To assess segmental versus non-segmental features in the ventral nervous system of Onychophorans, we screened the nerve cords for various markers, including synapsin, serotonin, gamma-aminobutyric acid, RFamide, dopamine, tyramine and octopamine. In addition, we performed retrograde fills of serially repeated commissures and leg nerves to localise the position of neuronal somata supplying those. Our data revealed a mixture of segmental and non-segmental elements within the Onychophoran nervous system. Conclusions We suggest that the segmental ganglia of arthropods evolved by a gradual condensation of subsets of neurons either in the arthropod or the arthropod-tardigrade lineage. These findings are in line with the hypothesis of gradual evolution of segmentation in panarthropods and thus contradict a loss of ancestral segmentation within the Onychophoran lineage.
-
evolution of pigment dispersing factor neuropeptides in panarthropoda insights from Onychophora velvet worms and tardigrada water bears
The Journal of Comparative Neurology, 2015Co-Authors: Georg Mayer, Paul A. Stevenson, Lars Hering, Juliane M Stosch, Heinrich DircksenAbstract:Pigment-dispersing factor (PDF) denotes a conserved family of homologous neuropeptides present in several invertebrate groups, including mollusks, nematodes, insects, and crustaceans (referred to here as pigment-dispersing hormone [PDH]). With regard to their encoding genes (pdf, pdh), insects possess only one, nematodes two, and decapod crustaceans up to three, but their phylogenetic relationship is unknown. To shed light on the origin and diversification of pdf/pdh homologs in Panarthropoda (Onychophora + Tardigrada + Arthropoda) and other molting animals (Ecdysozoa), we analyzed the transcriptomes of five distantly related Onychophorans and a representative tardigrade and searched for putative pdf homologs in publically available genomes of other protostomes. This revealed only one pdf homolog in several mollusk and annelid species; two in Onychophora, Priapulida, and Nematoda; and three in Tardigrada. Phylogenetic analyses suggest that the last common ancestor of Panarthropoda possessed two pdf homologs, one of which was lost in the arthropod or arthropod/tardigrade lineage, followed by subsequent duplications of the remaining homolog in some taxa. Immunolocalization of PDF-like peptides in six Onychophoran species, by using a broadly reactive antibody that recognizes PDF/PDH peptides in numerous species, revealed an elaborate system of neurons and fibers in their central and peripheral nervous systems. Large varicose projections in the heart suggest that the PDF neuropeptides functioned as both circulating hormones and locally released transmitters in the last common ancestor of Onychophora and Arthropoda. The lack of PDF-like-immunoreactive somata associated with the Onychophoran optic ganglion conforms to the hypothesis that Onychophoran eyes are homologous to the arthropod median ocelli. J. Comp. Neurol. 523:1865–1885, 2015 © 2015 Wiley Periodicals, Inc.
-
Evolution of pigment‐dispersing factor neuropeptides in panarthropoda: Insights from Onychophora (velvet worms) and tardigrada (water bears)
The Journal of comparative neurology, 2015Co-Authors: Georg Mayer, Paul A. Stevenson, Lars Hering, Juliane M Stosch, Heinrich DircksenAbstract:Pigment-dispersing factor (PDF) denotes a conserved family of homologous neuropeptides present in several invertebrate groups, including mollusks, nematodes, insects, and crustaceans (referred to here as pigment-dispersing hormone [PDH]). With regard to their encoding genes (pdf, pdh), insects possess only one, nematodes two, and decapod crustaceans up to three, but their phylogenetic relationship is unknown. To shed light on the origin and diversification of pdf/pdh homologs in Panarthropoda (Onychophora + Tardigrada + Arthropoda) and other molting animals (Ecdysozoa), we analyzed the transcriptomes of five distantly related Onychophorans and a representative tardigrade and searched for putative pdf homologs in publically available genomes of other protostomes. This revealed only one pdf homolog in several mollusk and annelid species; two in Onychophora, Priapulida, and Nematoda; and three in Tardigrada. Phylogenetic analyses suggest that the last common ancestor of Panarthropoda possessed two pdf homologs, one of which was lost in the arthropod or arthropod/tardigrade lineage, followed by subsequent duplications of the remaining homolog in some taxa. Immunolocalization of PDF-like peptides in six Onychophoran species, by using a broadly reactive antibody that recognizes PDF/PDH peptides in numerous species, revealed an elaborate system of neurons and fibers in their central and peripheral nervous systems. Large varicose projections in the heart suggest that the PDF neuropeptides functioned as both circulating hormones and locally released transmitters in the last common ancestor of Onychophora and Arthropoda. The lack of PDF-like-immunoreactive somata associated with the Onychophoran optic ganglion conforms to the hypothesis that Onychophoran eyes are homologous to the arthropod median ocelli. J. Comp. Neurol. 523:1865–1885, 2015 © 2015 Wiley Periodicals, Inc.
-
Spectral sensitivity in Onychophora (velvet worms) revealed by electroretinograms, phototactic behaviour and opsin gene expression.
The Journal of experimental biology, 2015Co-Authors: Holger Beckmann, Paul A. Stevenson, Lars Hering, Miriam J Henze, Almut Kelber, Georg MayerAbstract:Onychophorans typically possess a pair of simple eyes, inherited from the last common ancestor of Panarthropoda (Onychophora+Tardigrada+Arthropoda). These visual organs are thought to be homologous to the arthropod median ocelli, whereas the compound eyes probably evolved in the arthropod lineage. To gain insights into the ancestral function and evolution of the visual system in panarthropods, we investigated phototactic behaviour, opsin gene expression and the spectral sensitivity of the eyes in two representative species of Onychophora: Euperipatoides rowelli (Peripatopsidae) and Principapillatus hitoyensis (Peripatidae). Our behavioural analyses, in conjunction with previous data, demonstrate that both species exhibit photonegative responses to wavelengths ranging from ultraviolet to green light (370-530 nm), and electroretinograms reveal that the Onychophoran eye is maximally sensitive to blue light (peak sensitivity ∼480 nm). Template fits to these sensitivities suggest that the Onychophoran eye is monochromatic. To clarify which type of opsin the single visual pigment is based on, we localised the corresponding mRNA in the Onychophoran eye and brain using in situ hybridization. Our data show that the r-opsin gene (onychopsin) is expressed exclusively in the photoreceptor cells of the eye, whereas c-opsin mRNA is confined to the optic ganglion cells and the brain. Together, our findings suggest that the onychopsin is involved in vision, whereas c-opsin might have a photoreceptive, non-visual function in Onychophorans.
-
Selective neuronal staining in tardigrades and Onychophorans provides insights into the evolution of segmental ganglia in panarthropods
BMC Evolutionary Biology, 2013Co-Authors: Georg Mayer, Christine Martin, Paul A. Stevenson, Hans Joachim Pflüger, Jan Rüdiger, Susann Kauschke, Izabela Poprawa, Karin Hohberg, Ralph O Schill, Martin SchlegelAbstract:Background Although molecular analyses have contributed to a better resolution of the animal tree of life, the phylogenetic position of tardigrades (water bears) is still controversial, as they have been united alternatively with nematodes, arthropods, Onychophorans (velvet worms), or Onychophorans plus arthropods. Depending on the hypothesis favoured, segmental ganglia in tardigrades and arthropods might either have evolved independently, or they might well be homologous, suggesting that they were either lost in Onychophorans or are a synapomorphy of tardigrades and arthropods. To evaluate these alternatives, we analysed the organisation of the nervous system in three tardigrade species using antisera directed against tyrosinated and acetylated tubulin, the amine transmitter serotonin, and the invertebrate neuropeptides FMRFamide, allatostatin and perisulfakinin. In addition, we performed retrograde staining of nerves in the Onychophoran Euperipatoides rowelli in order to compare the serial locations of motor neurons within the nervous system relative to the appendages they serve in arthropods, tardigrades and Onychophorans. Results Contrary to a previous report from a Macrobiotus species, our immunocytochemical and electron microscopic data revealed contralateral fibres and bundles of neurites in each trunk ganglion of three tardigrade species, including Macrobiotus cf. harmsworthi , Paramacrobiotus richtersi and Hypsibius dujardini . Moreover, we identified additional, extra-ganglionic commissures in the interpedal regions bridging the paired longitudinal connectives. Within the ganglia we found serially repeated sets of serotonin- and RFamid-like immunoreactive neurons. Furthermore, our data show that the trunk ganglia of tardigrades, which include the somata of motor neurons, are shifted anteriorly with respect to each corresponding leg pair, whereas no such shift is evident in the arrangement of motor neurons in the Onychophoran nerve cords. Conclusions Taken together, these data reveal three major correspondences between the segmental ganglia of tardigrades and arthropods, including (i) contralateral projections and commissures in each ganglion, (ii) segmentally repeated sets of immunoreactive neurons, and (iii) an anteriorly shifted (parasegmental) position of ganglia. These correspondences support the homology of segmental ganglia in tardigrades and arthropods, suggesting that these structures were either lost in Onychophora or, alternatively, evolved in the tardigrade/arthropod lineage.
Lars Hering - One of the best experts on this subject based on the ideXlab platform.
-
File F1 from Halloween genes in panarthropods and the evolution of the early moulting pathway in Ecdysozoa
2018Co-Authors: Isabell Schumann, Lars Hering, Nathan Kenny, Jerome Hui, Georg MayerAbstract:List of species names and genes with NCBI or UniProt accession number used for phylogenetic analyses of neverland, Halloween genes, nuclear receptor genes, Early genes, and CYP18A1. Identified sequences of Euperipatoides rowelli (Onychophora) and Hypsibius exemplaris (Tardigrada) are included on table 7 and 8, respectively
-
Unexplored Character Diversity in Onychophora (Velvet Worms): A Comparative Study of Three Peripatid Species
2016Co-Authors: Ivo De Sena Oliveira, Lars Hering, Franziska Anni Franke, David M Rowell, Stefan Schaffer, Andreas Weck-heimann, Bernal Morera-brenes, Georg MayerAbstract:Low character variation among Onychophoran species has been an obstacle for taxonomic and phylogenetic studies in the past, however we have identified a number of new and informative characters using morphological, molecular, and chromosomal techniques. Our analyses involved a detailed examination of Epiperipatus biolleyi from Costa Rica, Eoperipatus sp. from Thailand, and a new Onychophoran species and genus from Costa Rica, Principapillatus hitoyensis gen. et sp. nov.. Scanning electron microscopy on embryos and specimens of varying age revealed novel morphological characters and character states, including the distribution of different receptor types along the antennae, the arrangement and form of papillae on the head, body and legs, the presence and shape of interpedal structures and fields of modified scales on the ventral body surface, the arrangement of lips around the mouth, the number, position and structure of crural tubercles and anal gland openings, and the presence and shape of embryonic foot projections. Karyotypic analyses revealed differences in the number and size of chromosomes among the species studied. The results of our phylogenetic analyses using mitochondrial COI and 12S rRNA gene sequences are in line with morphological and karyotype data. However, our data show a large number of unexplored, albeit informative, characters in the Peripatidae. We suggest that analysing these characters in additional species would help unravel species diversity and phylogeny in the Onychophora, and tha
-
Immunolocalization of arthropsin in the Onychophoran Euperipatoides rowelli (Peripatopsidae)
Frontiers Media S.A., 2016Co-Authors: Isabell Schumann, Lars Hering, Georg MayerAbstract:Opsins are light-sensitive proteins that play a key role in animal vision and are related to the ancient photoreceptive molecule rhodopsin found in unicellular organisms. In general, opsins involved in vision comprise two major groups: the rhabdomeric (r-opsins) and the ciliary opsins (c-opsins). The functionality of opsins, which is dependent on their protein structure, may have changed during evolution. In arthropods, typically r-opsins are responsible for vision, whereas in vertebrates c-opsins are components of visual photoreceptors. Recently, an enigmatic r-opsin-like protein called arthropsin has been identified in various bilaterian taxa, including arthropods, lophotrochozoans and chordates, by performing transcriptomic and genomic analyses. Since the role of arthropsin and its distribution within the body are unknown, we immunolocalized this protein in a representative of Onychophora – Euperipatoides rowelli – an ecdysozoan taxon which is regarded as one of the closest relatives of Arthropoda. Our data show that arthropsin is expressed in the central nervous system of E. rowelli, including the brain and the ventral nerve cords, but not in the eyes. These findings are consistent with previous results based on reverse transcription PCR in a closely related Onychophoran species and suggest that arthropsin is a non-visual protein. Based on its distribution in the central brain region and the mushroom bodies, we speculate that the Onychophoran arthropsin might be either a photosensitive molecule playing a role in the circadian clock, or a non-photosensitive protein involved in olfactory pathways, or both
-
evolution of pigment dispersing factor neuropeptides in panarthropoda insights from Onychophora velvet worms and tardigrada water bears
The Journal of Comparative Neurology, 2015Co-Authors: Georg Mayer, Paul A. Stevenson, Lars Hering, Juliane M Stosch, Heinrich DircksenAbstract:Pigment-dispersing factor (PDF) denotes a conserved family of homologous neuropeptides present in several invertebrate groups, including mollusks, nematodes, insects, and crustaceans (referred to here as pigment-dispersing hormone [PDH]). With regard to their encoding genes (pdf, pdh), insects possess only one, nematodes two, and decapod crustaceans up to three, but their phylogenetic relationship is unknown. To shed light on the origin and diversification of pdf/pdh homologs in Panarthropoda (Onychophora + Tardigrada + Arthropoda) and other molting animals (Ecdysozoa), we analyzed the transcriptomes of five distantly related Onychophorans and a representative tardigrade and searched for putative pdf homologs in publically available genomes of other protostomes. This revealed only one pdf homolog in several mollusk and annelid species; two in Onychophora, Priapulida, and Nematoda; and three in Tardigrada. Phylogenetic analyses suggest that the last common ancestor of Panarthropoda possessed two pdf homologs, one of which was lost in the arthropod or arthropod/tardigrade lineage, followed by subsequent duplications of the remaining homolog in some taxa. Immunolocalization of PDF-like peptides in six Onychophoran species, by using a broadly reactive antibody that recognizes PDF/PDH peptides in numerous species, revealed an elaborate system of neurons and fibers in their central and peripheral nervous systems. Large varicose projections in the heart suggest that the PDF neuropeptides functioned as both circulating hormones and locally released transmitters in the last common ancestor of Onychophora and Arthropoda. The lack of PDF-like-immunoreactive somata associated with the Onychophoran optic ganglion conforms to the hypothesis that Onychophoran eyes are homologous to the arthropod median ocelli. J. Comp. Neurol. 523:1865–1885, 2015 © 2015 Wiley Periodicals, Inc.
-
Evolution of pigment‐dispersing factor neuropeptides in panarthropoda: Insights from Onychophora (velvet worms) and tardigrada (water bears)
The Journal of comparative neurology, 2015Co-Authors: Georg Mayer, Paul A. Stevenson, Lars Hering, Juliane M Stosch, Heinrich DircksenAbstract:Pigment-dispersing factor (PDF) denotes a conserved family of homologous neuropeptides present in several invertebrate groups, including mollusks, nematodes, insects, and crustaceans (referred to here as pigment-dispersing hormone [PDH]). With regard to their encoding genes (pdf, pdh), insects possess only one, nematodes two, and decapod crustaceans up to three, but their phylogenetic relationship is unknown. To shed light on the origin and diversification of pdf/pdh homologs in Panarthropoda (Onychophora + Tardigrada + Arthropoda) and other molting animals (Ecdysozoa), we analyzed the transcriptomes of five distantly related Onychophorans and a representative tardigrade and searched for putative pdf homologs in publically available genomes of other protostomes. This revealed only one pdf homolog in several mollusk and annelid species; two in Onychophora, Priapulida, and Nematoda; and three in Tardigrada. Phylogenetic analyses suggest that the last common ancestor of Panarthropoda possessed two pdf homologs, one of which was lost in the arthropod or arthropod/tardigrade lineage, followed by subsequent duplications of the remaining homolog in some taxa. Immunolocalization of PDF-like peptides in six Onychophoran species, by using a broadly reactive antibody that recognizes PDF/PDH peptides in numerous species, revealed an elaborate system of neurons and fibers in their central and peripheral nervous systems. Large varicose projections in the heart suggest that the PDF neuropeptides functioned as both circulating hormones and locally released transmitters in the last common ancestor of Onychophora and Arthropoda. The lack of PDF-like-immunoreactive somata associated with the Onychophoran optic ganglion conforms to the hypothesis that Onychophoran eyes are homologous to the arthropod median ocelli. J. Comp. Neurol. 523:1865–1885, 2015 © 2015 Wiley Periodicals, Inc.
Graham E Budd - One of the best experts on this subject based on the ideXlab platform.
-
Analysis of the Wnt gene repertoire in an Onychophoran provides new insights into the evolution of segmentation
EvoDevo, 2014Co-Authors: Mattias Hogvall, Nico Posnien, Anna Schönauer, Graham E Budd, Alistair P Mcgregor, Ralf JanssenAbstract:Background The Onychophora are a probable sister group to Arthropoda, one of the most intensively studied animal phyla from a developmental perspective. Pioneering work on the fruit fly Drosophila melanogaster and subsequent investigation of other arthropods has revealed important roles for Wnt genes during many developmental processes in these animals. Results We screened the embryonic transcriptome of the Onychophoran Euperipatoides kanangrensis and found that at least 11 Wnt genes are expressed during embryogenesis. These genes represent 11 of the 13 known subfamilies of Wnt genes. Conclusions Many Onychophoran Wnt genes are expressed in segment polarity gene-like patterns, suggesting a general role for these ligands during segment regionalization, as has been described in arthropods. During early stages of development, Wnt2 , Wnt4 , and Wnt5 are expressed in broad multiple segment-wide domains that are reminiscent of arthropod gap and Hox gene expression patterns, which suggests an early instructive role for Wnt genes during E. kanangrensis segmentation.
-
Analysis of the Wnt gene repertoire in an Onychophoran provides new insights into the evolution of segmentation
EvoDevo, 2014Co-Authors: Mattias Hogvall, Nico Posnien, Anna Schönauer, Graham E Budd, Alistair P Mcgregor, Ralf JanssenAbstract:Background The Onychophora are a probable sister group to Arthropoda, one of the most intensively studied animal phyla from a developmental perspective. Pioneering work on the fruit fly Drosophila melanogaster and subsequent investigation of other arthropods has revealed important roles for Wnt genes during many developmental processes in these animals. Results We screened the embryonic transcriptome of the Onychophoran Euperipatoides kanangrensis and found that at least 11 Wnt genes are expressed during embryogenesis. These genes represent 11 of the 13 known subfamilies of Wnt genes. Conclusions Many Onychophoran Wnt genes are expressed in segment polarity gene-like patterns, suggesting a general role for these ligands during segment regionalization, as has been described in arthropods. During early stages of development, Wnt2 , Wnt4 , and Wnt5 are expressed in broad multiple segment-wide domains that are reminiscent of arthropod gap and Hox gene expression patterns, which suggests an early instructive role for Wnt genes during E. kanangrensis segmentation.
-
deciphering the Onychophoran segmentation gene cascade gene expression reveals limited involvement of pair rule gene orthologs in segmentation but a highly conserved segment polarity gene network
Developmental Biology, 2013Co-Authors: Ralf Janssen, Graham E BuddAbstract:The hallmark of the arthropods is their segmented body, although origin of segmentation, however, is unresolved. In order to shed light on the origin of segmentation we investigated orthologs of pair rule genes (PRGs) and segment polarity genes (SPGs) in a member of the closest related sister-group to the arthropods, the Onychophorans. Our gene expression data analysis suggests that most of the Onychophoran PRGs do not play a role in segmentation. One possible exception is the even-skipped (eve) gene that is expressed in the posterior end of the Onychophoran where new segments are likely patterned, and is also expressed in segmentation-gene typical transverse stripes in at least a number of newly formed segments. Other Onychophoran PRGs such as runt (run), hairy/Hes (h/Hes) and odd-skipped (odd) do not appear to have a function in segmentation at all. Onychophoran PRGs that act low in the segmentation gene cascade in insects, however, are potentially involved in segment-patterning. Most obvious is that from the expression of the pairberry (pby) gene ortholog that is expressed in a typical SPG-pattern. Since this result suggested possible conservation of the SPG-network we further investigated SPGs (and associated factors) such as Notum in the Onychophoran. We find that the expression patterns of SPGs in arthropods and the Onychophoran are highly conserved, suggesting a conserved SPG-network in these two clades, and indeed also in an annelid. This may suggest that the common ancestor of lophotrochozoans and ecdysozoans was already segmented utilising the same SPG-network, or that the SPG-network was recruited independently in annelids and Onychophorans/arthropods.
-
Gene expression suggests conserved aspects of Hox gene regulation in arthropods and provides additional support for monophyletic Myriapoda
EvoDevo, 2010Co-Authors: Ralf Janssen, Graham E BuddAbstract:Antisense transcripts of Ultrabithorax (aUbx) in the millipede Glomeris and the centipede Lithobius are expressed in patterns complementary to that of the Ubx sense transcripts. A similar complementary expression pattern has been described for non-coding RNAs (ncRNAs) of the bithoraxoid (bxd) locus in Drosophila, in which the transcription of bxd ncRNAs represses Ubx via transcriptional interference. We discuss our findings in the context of possibly conserved mechanisms of Ubx regulation in myriapods and the fly. Bicistronic transcription of Ubx and Antennapedia (Antp) has been reported previously for a myriapod and a number of crustaceans. In this paper, we show that Ubx/Antp bicistronic transcripts also occur in Glomeris and an Onychophoran, suggesting further conserved mechanisms of Hox gene regulation in arthropods. Myriapod monophyly is supported by the expression of aUbx in all investigated myriapods, whereas in other arthropod classes, including the Onychophora, aUbx is not expressed. Of the two splice variants of Ubx/Antp only one could be isolated from myriapods, representing a possible further synapomorphy of the Myriapoda.
-
The involvement of engrailed and wingless during segmentation in the Onychophoran Euperipatoides kanangrensis (Peripatopsidae: Onychophora) (Reid 1996)
Development Genes and Evolution, 2009Co-Authors: Bo Joakim Eriksson, Graham E Budd, Noel N. Tait, Michael AkamAbstract:As the putative sister group to the arthropods, Onychophorans can provide insight into ancestral developmental mechanisms in the panarthropod clade. Here, we examine the expression during segmentation of orthologues of wingless (Wnt1) and engrailed , two genes that play a key role in defining segment boundaries in Drosophila and that appear to play a role in segmentation in many other arthropods. Both are expressed in segmentally reiterated stripes in all forming segments except the first (brain) segment, which only shows an engrailed stripe. Engrailed is expressed before segments are morphologically visible and is expressed in both mesoderm and ectoderm. Segmental wingless expression is not detectable until after mesodermal somites are clearly distinct. Early engrailed expression lies in and extends to both sides of the furrow that first demarcates segments in the ectoderm, but is largely restricted to the posterior part of somites. Wingless expression lies immediately anterior to engrailed expression, as it does in many arthropods, but there is no precise cellular boundary between the two expression domains analogous to the overt parasegment boundary seen in Drosophila . Engrailed stripes extend along the posterior part of each limb bud, including the antenna, while wingless is restricted to the distal tip of the limbs and the neurectoderm basal to the limbs.