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Paul M. Macdonald - One of the best experts on this subject based on the ideXlab platform.
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A late phase of Oskar accumulation is crucial for posterior Patterning of the Drosophila embryo, and is blocked by ectopic expression of Bruno.
Differentiation; research in biological diversity, 2007Co-Authors: Mark J. Snee, Dianne Harrison, Nan Yan, Paul M. MacdonaldAbstract:In Drosophila, posterior embryonic Body Patterning and germ cell formation rely on Oskar, a protein that is concentrated at the posterior pole of the oocyte. A program of mRNA localization and translational regulation ensures that Oskar is only expressed at the proper location. One key regulatory factor is Bruno, which represses translation of oskar mRNA before its localization. Ectopic expression of a bruno cDNA prolongs repression, even after oskar mRNA is localized, and posterior Body Patterning is efficiently and selectively blocked. Surprisingly, the initial accumulation of Oskar, while frequently reduced, is not eliminated, arguing that levels of Oskar previously thought to be sufficient for Patterning do not suffice, or that Bruno acts at a downstream step in Patterning. Expression of the bruno cDNA does not inhibit posterior Patterning when Oskar is expressed independent of Bruno-mediated regulation, ruling out a downstream requirement for Bruno. Notably, an Oskar::GFP reporter protein reveals continual accumulation during the late phases of oogenesis. Taken together, these results strongly argue that a late phase in accumulation of Osk protein, typically not monitored because of imperviousness of late stage oocytes to antibodies, is crucial for Body Patterning.
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aubergine encodes a drosophila polar granule component required for pole cell formation and related to eif2c
Development, 2001Co-Authors: Adam N Harris, Paul M. MacdonaldAbstract:In Drosophila oocytes, activation of Oskar translation from a transcript localized to the posterior pole is an essential step in the organization of the pole plasm, specialized cytoplasm that contains germline and abdominal Body Patterning determinants. Oskar is a component of polar granules, large particles associated with the pole plasm and the germline precursor pole cells of the embryo. aubergine mutants fail to translate oskar mRNA efficiently and are thus defective in posterior Body Patterning and pole cell formation. We have found that Aubergine protein is related to eukaryotic translation initiation factor 2C and suggest how it may activate translation. In addition, we found that Aubergine was recruited to the posterior pole in a vas-dependent manner and is itself a polar granule component. Consistent with its presence in these structures, Aubergine is required for pole cell formation independently of its initial role in oskar translation. Unlike two other known polar granule components, Vasa and Oskar, Aubergine remains cytoplasmic after pole cell formation, suggesting that the roles of these proteins diverge during embryogenesis.
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bsf binds specifically to the bicoid mrna 3 untranslated region and contributes to stabilization of bicoid mrna
Molecular and Cellular Biology, 2001Co-Authors: Ricardo Mancebo, Paul M. Macdonald, Xiulan Zhou, Wendy Shillinglaw, William J HenzelAbstract:The early stages of Drosophila melanogaster development rely extensively on posttranscriptional forms of gene regulation. Deployment of the anterior Body Patterning morphogen, the Bicoid protein, requires both localization and translational regulation of the maternal bicoid mRNA. Here we provide evidence that the bicoid mRNA is also selectively stabilized during oogenesis. We identify and isolate a protein, BSF, that binds specifically to IV/V RNA, a minimal form of the bicoid mRNA 3′ untranslated region that supports a normal program of mRNA localization during oogenesis. Mutations that disrupt the BSF binding site in IV/V RNA or substantially reduce the level of BSF protein lead to reduction in IV/V RNA levels, indicating a role for BSF in RNA stabilization. The BSF protein is novel and lacks all of the characterized RNA binding motifs. However, BSF does include multiple copies of the PPR motif, whose function is unknown but appears in other proteins with roles in RNA metabolism.
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aubergine enhances oskar translation in the Drosophila ovary
Development (Cambridge England), 1996Co-Authors: Joan E. Wilson, Joanne E. Connell, Paul M. MacdonaldAbstract:Although translational regulation of maternal mRNA is important for proper development of the Drosophila embryo, few genes involved in this process have been identified. In this report, we describe the role of aubergine in oskar translation. Previously, aubergine has been implicated in dorsoventral Patterning, as eggs from aubergine mutant mothers are ventralized and seldom fertilized (Schupbach, T. and Wieschaus, E. (1991) Genetics 129, 1119–1136). We have isolated two new alleles of aubergine in a novel genetic screen and have shown that aubergine is also required for posterior Body Patterning, as the small fraction of eggs from aubergine- mothers that are fertilized develop into embryos which lack abdominal segmentation. Although aubergine mutations do not appear to affect the stability of either oskar mRNA or protein, the level of oskar protein is significantly reduced in aubergine mutants. Thus, aubergine is required to enhance oskar translation. While aubergine-dependence is conferred upon oskar mRNA by sequences in the oskar 3′ UTR, aubergine may influence oskar translation through an interaction with sequences upstream of the oskar 3′ UTR.
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translational regulation of oskar mrna by bruno an ovarian rna binding protein is essential
Cell, 1995Co-Authors: Jeongsil Kimha, Karen Kerr, Paul M. MacdonaldAbstract:Abstract Oskar (osk) protein directs the deployment of nanos (nos) , the posterior Body-Patterning morphogen in Drosophila. To avoid inappropriate activation of nos, osk activity must appear only at the posterior pole of the oocyte, where the osk mRNA becomes localized during oogenesis. Here, we show that translation of osk mRNA is, and must be, repressed prior to its localization; absence of repression allows osk protein to accumulate throughout the oocyte, specifying posterior Body Patterning throughout the embryo. Translational repression is mediated by an ovarian protein, bruno, that binds specifically to bruno response elements (BREs), present in multiple copies in the osk mRNA 3′UTR. Addition of BREs to a heterologous mRNA renders it sensitive to translational repression in the ovary.
Chuanchin Chiao - One of the best experts on this subject based on the ideXlab platform.
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morphological changes of the optic lobe from late embryonic to adult stages in oval squids sepioteuthis lessoniana
Journal of Morphology, 2018Co-Authors: Wensung Chung, Chunchieh Yu, Chiahao Su, Funglan Chan, Justin N Marshall, Chuanchin ChiaoAbstract:The optic lobe is the largest brain area within the central nervous system of cephalopods and it plays important roles in the processing of visual information, the regulation of Body Patterning, and locomotive behavior. The oval squid Sepioteuthis lessoniana has relatively large optic lobes that are responsible for visual communication via dynamic Body Patterning. It has been observed that the visual behaviors of oval squids change as the animals mature, yet little is known about how the structure of the optic lobes changes during development. The aim of the present study was to characterize the ontogenetic changes in neural organization of the optic lobes of S. lessoniana from late embryonic stage to adulthood. Magnetic resonance imaging and micro-CT scans were acquired to reconstruct the 3D-structure of the optic lobes and examine the external morphology at different developmental stages. In addition, optic lobe slices with nuclear staining were used to reveal changes in the internal morphology throughout development. As oval squids mature, the proportion of the brain making up the optic lobes increases continuously, and the optic lobes appear to have a prominent dent on the ventrolateral side. Inside the optic lobe, the cortex and the medulla expand steadily from the late embryonic stage to adulthood, but the cell islands in the tangential zone of the optic lobe decrease continuously in parallel. Interestingly, the size of the nuclei of cells within the medulla of the optic lobe increases throughout development. These findings suggest that the optic lobe undergoes continuous external morphological change and internal neural reorganization throughout the oval squid's development. These morphological changes in the optic lobe are likely to be responsible for changes in the visuomotor behavior of oval squids from hatching to adulthood.
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neural organization of the optic lobe changes steadily from late embryonic stage to adulthood in cuttlefish sepia pharaonis
Frontiers in Physiology, 2017Co-Authors: Chiahao Su, Chuanchin ChiaoAbstract:The optic lobe is the largest structure in the cuttlefish brain. While the general morphology of the optic lobe in adult cuttlefish has been well described, the 3D structure and ontogenetic development of its neural organization have not been characterized. To correlate observed behavioral changes within the brain structure along the development of this animal, optic lobes from the late embryonic stage to adulthood were examined systematically in the present study. The MRI scan revealed that the so called “cell islands” in the medulla of the cephalopod’s optic lobe (Young, 1962; Young, 1974) are in fact a contiguous tree-like structure. Quantification of the neural organizational development of optic lobes showed that structural features of the cortex and radial column zone were established earlier than those of the tangential zone during embryonic and post-hatching stages. Within the cell islands, the density of nuclei was decreased while the size of nuclei was increased during the development. Furthermore, the visual processing area in the optic lobe showed a significant variation in lateralization during embryonic and juvenile stages. Our observation of a continuous increase in neural fibers and nucleus size in the tangential zone of the optic lobe from late embryonic stage to adulthood indicates that the neural organization of the optic lobe is modified along the development of cuttlefish. These findings thus support that the ontogenetic change of the optic lobe is responsible for their continuously increased complexity in Body Patterning and visuomotor behaviors.
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quantitative analysis of dynamic Body Patterning reveals the grammar of visual signals during the reproductive behavior of the oval squid sepioteuthis lessoniana
Frontiers in Ecology and Evolution, 2017Co-Authors: Chunyen Lin, Yuehchun Tsai, Chuanchin ChiaoAbstract:Cephalopods use a diverse range of Body patterns for visual communication. Each pattern is composed of several distinct chromatic components that are under neural control and are expressed dynamically. In the oval squid Sepioteuthis lessoniana, males use distinct Body patterns to interact with females and other males at the spawning site. To systematically examine their visual signals during reproductive behavior, an ethogram of 27 Body pattern components produced by S. lessoniana was observed in both the wild and captivity; these were then characterized. Five behaviors were commonly seen among these reproductively active squids, namely parallel swimming, male guarding, male-male fighting, male-parallel mating, and male-upturn mating. Each behavior was found to be composed of the expression in a temporal sequence of different chromatic components. By analyzing the dynamic Body Patterning time series associated with each behavior, it was found that a certain subset of components was expressed simultaneously or sequentially in response to conspecifics. Importantly, the results not only revealed that each behavior is composed of multiple chromatic components, but the findings also showed that each component is often associated with multiple behaviors. To gain insight into the visual communication associated with each behavior in terms of the Body Patterning's key components, the co-expression frequencies of two or more components at any moment in time were calculated in order to assess uniqueness when distinguishing one behavior from another. This approach identified the minimum set of key components that, when expressed together, represents an unequivocal visual communication signal. While the interpretation of the signal and the associated response of the receiver during visual communication are difficult to determine, the concept of the component assembly is similar to a typical language within which individual words often have multiple meanings, but when they appeared together with other words, the message becomes unequivocal. The present study thus demonstrates that dynamic Body pattering, by expressing unique sets of key components acutely, is an efficient way of communicating behavioral information between oval squids.
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mosaic organization of Body pattern control in the optic lobe of squids
The Journal of Neuroscience, 2017Co-Authors: Chuanchin ChiaoAbstract:Cephalopods in nature undergo highly dynamic skin coloration changes that allow rapid camouflage and intraspecies communication. The optic lobe is thought to play a key role in controlling the expansion of the chromatophores that generate these diverse Body patterns. However, the functional organization of the optic lobe and neural control of the various Body patterns by the optic lobe are largely unknown. We applied electrical stimulation within the optic lobe to investigate the neural basis of Body Patterning in the oval squid, Sepioteuthis lessoniana. Most areas in the optic lobe mediated predominately ipsilateral expansion of chromatophores present on the mantle, but not on the head and arms; furthermore, the expanded areas after electrical stimulation were positively correlated with an increase in stimulating voltage and stimulation depth. These results suggest a unilaterally dominant and vertically converged organization of the optic lobe. Furthermore, analyzing 14 of the elicited Body pattern components and their corresponding stimulation sites revealed that the same components can be elicited by stimulating different parts of the optic lobe and that various subsets of these components can be coactivated by stimulating the same area. These findings suggest that many Body pattern components may have multiple motor units in the optic lobe and that these are organized in a mosaic manner. The multiplicity associated with the nature of the neural controls of these components in the cephalopod brain thus reflects the versatility of the individual components during the generation of diverse Body patterns. SIGNIFICANCE STATEMENT Neural control of the dynamic Body Patterning of cephalopods for camouflage and intraspecies communication is a fascinating research topic. Previous studies have shown that the optic lobe is the motor command center for dynamic Body Patterning. However, little is known about its neural organization and the mechanisms underlying its control of Body pattern generation. By electrically stimulating the optic lobe of the oval squids and observing their Body pattern changes, surprisingly, we found that there is no somatotopic organization of motor units. Instead, many of these components have multiple motor units within the optic lobe and are organized in a mosaic manner. The present work reveals a novel neural control of dynamic Body Patterning for communication in cephalopods.
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cuttlefish camouflage the effects of substrate contrast and size in evoking uniform mottle or disruptive Body patterns
Vision Research, 2008Co-Authors: Alexandra Barbosa, Chuanchin Chiao, Lydia M. Mäthger, Kendra C. Buresch, Charles Chubb, Jennifer Kelly, Roger T. HanlonAbstract:Cuttlefish are cephalopod molluscs that achieve dynamic camouflage by rapidly extracting visual information from the background and neurally implementing an appropriate skin (or Body) pattern. We investigated how cuttlefish Body Patterning responses are influenced by contrast and spatial scale by varying the contrast and the size of checkerboard backgrounds. We found that: (1) at high contrast levels, cuttlefish Body Patterning depended on check size; (2) for low contrast levels, Body Patterning was independent of "check" size; and (3) on the same check size, cuttlefish fine-tuned the contrast and fine structure of their Body patterns, in response to small contrast changes in the background. Furthermore, we developed an objective, automated method of assessing cuttlefish camouflage patterns that quantitatively differentiated the three Body patterns of uniform/stipple, mottle and disruptive. This study draws attention to the key roles played by background contrast and particle size in determining an effective camouflage pattern.
Roger T. Hanlon - One of the best experts on this subject based on the ideXlab platform.
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adaptive Body Patterning three dimensional skin morphology and camouflage measures of the slender filefish monacanthus tuckeri on a caribbean coral reef
Biological Journal of The Linnean Society, 2015Co-Authors: Roger T. Hanlon, Justine J Allen, Derya Akkaynak, Arthur U SugdenAbstract:The slender filefish is a master of adaptive camouflage and can change its appearance within 1–3 s. Videos and photographs of this animal’s cryptic Body Patterning and behavior were collected in situ under natural light on a Caribbean coral reef. We present an ethogram of Body Patterning components that includes large- and small-scale spots, stripes and bars that confer a variety of cryptic patterns amidst a range of complex backgrounds. Field images were analyzed to investigate two aspects of camouflage effectiveness: (1) the degree of colour resemblance between animals and their nearby visual stimuli; and (2) the visibility of each fish’s actual Body outline vs. its illusory outline. Most animals more closely matched the colour of nearby visual stimuli than that of the surrounding background. Three-dimensional dermal flaps complement the melanophore skin patterns by enhancing the complexity of the fish’s physical skin texture to disguise its actual Body shape, and the morphology of these structures was studied. The results suggest that the Body patterns, skin texture, postures and swimming orientations putatively hinder both the detection and recognition of the fish by potential visual predators. Overall, the rapid speed of change of multiple patterns, colour blending with nearby backgrounds, and the physically complicated edge produced by dermal flaps effectively camouflage this animal among soft corals and macroalgae in the Caribbean Sea. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 116, 377–396.
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graded behavioral responses and habituation to sound in the common cuttlefish sepia officinalis
The Journal of Experimental Biology, 2014Co-Authors: Julia E Samson, T A Mooney, Sander W S Gussekloo, Roger T. HanlonAbstract:Sound is a widely available and vital cue in aquatic environments, yet most bioacoustic research has focused on marine vertebrates, leaving sound detection in invertebrates poorly understood. Cephalopods are an ecologically key taxon that likely use sound and may be impacted by increasing anthropogenic ocean noise, but little is known regarding their behavioral responses or adaptations to sound stimuli. These experiments identify the acoustic range and levels that elicit a wide range of secondary defense behaviors such as inking, jetting and rapid coloration change. Secondarily, it was found that cuttlefish habituate to certain sound stimuli. The present study examined the behavioral responses of 22 cuttlefish ( Sepia officinalis ) to pure-tone pips ranging from 80 to 1000 Hz with sound pressure levels of 85–188 dB re. 1 μPa rms and particle accelerations of 0–17.1 m s –2 . Cuttlefish escape responses (inking, jetting) were observed between frequencies of 80 and 300 Hz and at sound levels above 140 dB re. 1 μPa rms and 0.01 m s –2 (0.74 m s –2 for inking responses). Body Patterning changes and fin movements were observed at all frequencies and sound levels. Response intensity was dependent upon stimulus amplitude and frequency, suggesting that cuttlefish also possess loudness perception with a maximum sensitivity around 150 Hz. Cuttlefish habituated to repeated 200 Hz tone pips, at two sound intensities. Total response inhibition was not reached, however, and a basal response remained present in most animals. The graded responses provide a loudness sensitivity curve and suggest an ecological function for sound use in cephalopods.
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cuttlefish camouflage the effects of substrate contrast and size in evoking uniform mottle or disruptive Body patterns
Vision Research, 2008Co-Authors: Alexandra Barbosa, Chuanchin Chiao, Lydia M. Mäthger, Kendra C. Buresch, Charles Chubb, Jennifer Kelly, Roger T. HanlonAbstract:Cuttlefish are cephalopod molluscs that achieve dynamic camouflage by rapidly extracting visual information from the background and neurally implementing an appropriate skin (or Body) pattern. We investigated how cuttlefish Body Patterning responses are influenced by contrast and spatial scale by varying the contrast and the size of checkerboard backgrounds. We found that: (1) at high contrast levels, cuttlefish Body Patterning depended on check size; (2) for low contrast levels, Body Patterning was independent of "check" size; and (3) on the same check size, cuttlefish fine-tuned the contrast and fine structure of their Body patterns, in response to small contrast changes in the background. Furthermore, we developed an objective, automated method of assessing cuttlefish camouflage patterns that quantitatively differentiated the three Body patterns of uniform/stipple, mottle and disruptive. This study draws attention to the key roles played by background contrast and particle size in determining an effective camouflage pattern.
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disruptive Body Patterning of cuttlefish sepia officinalis requires visual information regarding edges and contrast of objects in natural substrate backgrounds
The Biological Bulletin, 2005Co-Authors: Chuanchin Chiao, Emma J Kelman, Roger T. HanlonAbstract:Cuttlefish (Sepia officinalis Linnaeus, 1758) on mixed light and dark gravel show disruptive Body patterns for camouflage. This response is evoked when the size of the gravel is equivalent to the area of the “White square,” a component of its dorsal mantle patterns. However, the features of natural substrates that cuttlefish cue on visually are largely unknown. Therefore, we aimed to identify those visual features of background objects that are required to evoke disruptive coloration. At first, we put young cuttlefish in a circular experimental arena, presented them with natural gravel and photographs of natural gravel, and established that the animals would show a disruptive pattern when presented either with three-dimensional natural gravel or its two-dimensional photographic representation. We then manipulated the digital photographs by applying (i) a low-pass filter to remove the edges of the fragments of gravel, and (ii) a high-pass filter to remove the contrast among them. The Body patterns produced by the cuttlefish in response to these altered visual stimuli were then videorecorded and graded. The results show that, to evoke disruptive coloration in cuttlefish, visual information about the edges and contrast of objects within natural substrate backgrounds is required. Cephalopods have a remarkable ability to change the color and pattern of their skin, and research has demonstrated that visual input regulates these changes. Cuttlefish skin can show 20‐50 chromatophore patterns that are used
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an ethogram of Body Patterning behavior in the biomedically and commercially valuable squid loligo pealei off cape cod massachusetts
The Biological Bulletin, 1999Co-Authors: Roger T. Hanlon, Michael R Maxwell, Nadav Shashar, Ellis R Loew, Kimlaura BoyleAbstract:Squids have a wide repertoire of Body patterns; these patterns contain visual signals assembled from a highly diverse inventory of chromatic, postural, and loco motor components. The chromatic components reflect the activity of dermal chromatophore organs that, like the pos tural and locomotor muscles, are controlled directly from the central nervous system. Because a thorough knowledge of Body patterns is fundamental to an understanding of squid behavior, we have compiled and described an etho gram (a catalog of Body patterns and associated behaviors) for Loligo pea!ei. Observations of this species were made over a period of three years (440 h) and under a variety of behavioral circumstances. The natural behavior of the squid was filmed on spawning grounds off Cape Cod (northwest em Atlantic), and behavioral trials in the laboratory were run in large tanks. The Body pattern componentsâ€"34 chro matic (including 4 polarization components), 5 postural, and 12 locomotorâ€"are each described in detail. Eleven of the most common Body patterns are also described. Four of them are chronic, or long-lasting, patterns for crypsis; an example is Banded Bottom Sitting, which produces disrup tive coloration against the substrate. The remaining seven patterns are acute; they are mostly used in intraspecific communication among spawning squids. Two of these acute patternsâ€"Lateral Display and Mate Guarding Patternâ€"are used during agonistic bouts and mate guarding; they are visually bright and conspicuous, which may subject the squids to predation; but we hypothesize that schooling and diurnal activity may offset the disadvantage presented by
Nigel C Hughes - One of the best experts on this subject based on the ideXlab platform.
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the development of the silurian trilobite aulacopleura koninckii reconstructed by applying inferred growth and segmentation dynamics a case study in paleo evo devo
Frontiers in Ecology and Evolution, 2017Co-Authors: Nigel C Hughes, Paul S Hong, Giuseppe FuscoAbstract:Fossilized growth series provide rare glimpses into the development of ancient organisms, illustrating descriptively how size and shape changed through ontogeny. Occasionally fossil preservation is such that it is feasible to test alternative possibilities about how ancient development was regulated. Here we apply inferred developmental parameters pertaining to size, shape, and segmentation in the abundant and well-preserved 429 Myr old trilobite Aulacopleura koninckii that we have investigated previously to reconstruct the post-embryonic ontogeny of this ancient arthropod. Our published morphometric analyses associated with model testing have shown that: specification of the adult number of trunk segments (polymorphic in this species) was determined precociously in ontogeny; that growth regulation was targeted (i.e., compensatory), such that each developmental stage exhibited comparable variance in size and shape; and that growth gradients operating along the main Body axis, both during juvenile and adult ontogeny, resulted from a form of growth control based on positional specification. While such developmental features are common among extant organisms, our results represent the oldest evidence for them within Metazoa. Herein, the novel reconstruction of the development of A. koninckii permits visualization of patterns of relative and absolute growth and segmentation as never before possible for a fossilized arthropod ontogeny. By conducting morphometric analysis of appropriate data sets it is thus possible to move beyond descriptive ontogenetic studies and to address questions of high interest for evolutionary developmental biology using data from fossils, which can help elucidate both how developmental processes themselves evolve and how they affect the evolution of organismal Body Patterning. By extending similar analyses to other cases of exceptional preservation of fossilized ontogeny, we can anticipate beginning to realize the research program of “paleo-evo-devo”.
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the evolution of trilobite Body Patterning
Annual Review of Earth and Planetary Sciences, 2007Co-Authors: Nigel C HughesAbstract:The good fossil record of trilobite exoskeletal anatomy and ontogeny, coupled with information on their nonbiomineralized tissues, permits analysis of how the trilobite Body was organized and developed, and the various evolutionary modifications of such Patterning within the group. In several respects trilobite development and form appears comparable with that which may have characterized the ancestor of most or all euarthropods, giving studies of trilobite Body organization special relevance in the light of recent advances in the understanding of arthropod evolution and development. The Cambrian diversification of trilobites displayed modifications in the Patterning of the trunk region comparable with those seen among the closest relatives of Trilobita. In contrast, the Ordovician diversification of trilobites, although contributing greatly to the overall diversity within the clade, did so within a narrower range of trunk conditions. Trilobite evolution is consistent with an increased premium on effective enrollment and protective strategies, and with an evolutionary trade-off between the flexibility to vary the number of trunk segments and the ability to regionalize portions of the trunk.
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trilobite Body Patterning and the evolution of arthropod tagmosis
BioEssays, 2003Co-Authors: Nigel C HughesAbstract:Summary Preservationpermittingpatternsofdevelopmentalevolution can be reconstructed within long extinct clades, and the rich fossil record of trilobite ontogeny and phylogeny provides an unparalleled opportunity for doing so. Furthermore, knowledge of Hox gene expression patterns among living arthropods permit inferences about possible Hox gene deployment in trilobites. The trilobite anteroposterior Body plan is consistent with recent suggestions that basal euarthropods had a relatively low degree of tagmosis among cephalic limbs, possibly related to overlapping expression domains of cephalic Hox genes. Trilobite trunk segments appeared sequentially at a subterminal generative zone, and were exchanged between regions of fused and freely articulating segments during growth. Homonomous trunk segment shape and gradual size transition were apparently phylogenetically basal conditions and suggest a single trunk tagma. Several derived clades independently evolved functionally distinct tagmata within the trunk, apparently exchanging flexible segment numbers for greater regionally autonomy. The trilobite trunk chronicles how different aspects of arthropod segmentation coevolved as the degree of tagmosis increased. BioEssays 25:386–395, 2003. 2003 Wiley Periodicals, Inc.
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trilobite tagmosis and Body Patterning from morphological and developmental perspectives
Integrative and Comparative Biology, 2003Co-Authors: Nigel C HughesAbstract:SYNOPSIS. The Trilobita were characterized by a cephalic region in which the biomineralized exoskeleton showed relatively high morphological differentiation among a taxonomically stable set of well defined segments, and an ontogenetically and taxonomically dynamic trunk region in which both exoskeletal segments and ventral appendages were similar in overall form. Ventral appendages were homonomous biramous limbs throughout both the cephalon and trunk, except for the most anterior appendage pair that was antenniform, preoral, and uniramous, and a posteriormost pair of antenniform cerci, known only in one species. In some clades trunk exoskeletal segments were divided into two batches. In some, but not all, of these clades the boundary between batches coincided with the boundary between the thorax and the adult pygidium. The repeated differentiation of the trunk into two batches of segments from the homonomous trunk condition indicates an evolutionary trend in aspects of Body Patterning regulation that was achieved independently in several trilobite clades. The phylogenetic placement of trilobites and congruence of broad patterns of tagmosis with those seen among extant arthropods suggest that the expression domains of trilobite cephalic Hox genes may have overlapped in a manner similar to that seen among extant arachnates. This, coupled with the fact that trilobites likely possessed ten Hox genes, presents one alternative to a recent model in which Hox gene distribution in trilobites was equated to eight putative divisions of the trilobite Body plan.
Matthew C. Gibson - One of the best experts on this subject based on the ideXlab platform.
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Feeding-dependent tentacle development in the sea anemone Nematostella vectensis.
Nature communications, 2020Co-Authors: Aissam Ikmi, Petrus J. Steenbergen, Marie Anzo, Mason R. Mcmullen, Anniek Stokkermans, Lacey R Ellington, Matthew C. GibsonAbstract:In cnidarians, axial Patterning is not restricted to embryogenesis but continues throughout a prolonged life history filled with unpredictable environmental changes. How this developmental capacity copes with fluctuations of food availability and whether it recapitulates embryonic mechanisms remain poorly understood. Here we utilize the tentacles of the sea anemone Nematostella vectensis as an experimental paradigm for developmental Patterning across distinct life history stages. By analyzing over 1000 growing polyps, we find that tentacle progression is stereotyped and occurs in a feeding-dependent manner. Using a combination of genetic, cellular and molecular approaches, we demonstrate that the crosstalk between Target of Rapamycin (TOR) and Fibroblast growth factor receptor b (Fgfrb) signaling in ring muscles defines tentacle primordia in fed polyps. Interestingly, Fgfrb-dependent polarized growth is observed in polyp but not embryonic tentacle primordia. These findings show an unexpected plasticity of tentacle development, and link post-embryonic Body Patterning with food availability. How the developmental capacity of long-lived animals copes with fluctuations in the food supply is unclear. Here, the authors show using the sea anemone Nematostella vectensis that the crosstalk between Target of Rapamycin and fibroblast growth factor signalling in ring muscles links postembryonic tentacle Patterning with food availability.
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Feeding-dependent tentacle development in the sea anemone Nematostella vectensis
2020Co-Authors: Aissam Ikmi, Petrus J. Steenbergen, Marie Anzo, Mason R. Mcmullen, Anniek Stokkermans, Lacey R Ellington, Matthew C. GibsonAbstract:Summary In cnidarians, axial Patterning is not restricted to embryonic development but continues throughout a prolonged life history filled with unpredictable environmental changes. How this developmental capacity copes with fluctuations of food availability and whether it recapitulates embryonic mechanisms remain poorly understood. To address these questions, we utilize the tentacles of the sea anemone Nematostella vectensis as a novel paradigm for developmental Patterning across distinct life history stages. As a result of embryonic development, Nematostella polyps feature four primary tentacles, while adults have 16 or more. By analyzing over 1000 growing polyps, we find that tentacle progression is remarkably stereotyped and occurs in a feeding-dependent manner. Mechanistically, we show that discrete Fibroblast growth factor receptor b (Fgfrb)-positive ring muscles prefigure the sites of new tentacles in unfed polyps. In response to feeding, a Target of Rapamycin (TOR)-dependent mechanism controls the expansion of Fgfrb expression in oral tissues which defines tentacle primordia. Using a combination of genetic, cellular and molecular approaches, we demonstrate that FGFRb regionally enhances TOR signaling activity and promotes polarized growth, a spatial pattern that is restricted to polyp but not to embryonic tentacle primordia. These findings reveal an unexpected plasticity of tentacle development, and show that the crosstalk between TOR-mediated nutrient signaling and FGFRb pathway couples post-embryonic Body Patterning with food availability.
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An axial Hox code controls tissue segmentation and Body Patterning in Nematostella vectensis.
Science (New York N.Y.), 2018Co-Authors: Florencia Del Viso, Aissam Ikmi, Chengyi Chen, Amanda E Kroesen, Matthew C. GibsonAbstract:Hox genes encode conserved developmental transcription factors that govern anterior-posterior (A-P) pattering in diverse bilaterian animals, which display bilateral symmetry. Although Hox genes are also present within Cnidaria, these simple animals lack a definitive A-P axis, leaving it unclear how and when a functionally integrated Hox code arose during evolution. We used short hairpin RNA (shRNA)–mediated knockdown and CRISPR-Cas9 mutagenesis to demonstrate that a Hox-Gbx network controls radial segmentation of the larval endoderm during development of the sea anemone Nematostella vectensis. Loss of Hox-Gbx activity also elicits marked defects in tentacle Patterning along the directive (orthogonal) axis of primary polyps. On the basis of our results, we propose that an axial Hox code may have controlled Body Patterning and tissue segmentation before the evolution of the bilaterian A-P axis.