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Daniel I Speiser - One of the best experts on this subject based on the ideXlab platform.
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Report A Chiton Uses Aragonite Lenses to Form Images
2020Co-Authors: Daniel I Speiser, Douglas J. EernisseAbstract:Summary Hundreds of ocelli are embedded in the dorsal shell plates of certain Chitons [1]. These ocelli each contain a pigment layer, retina, and lens [2], but it is unknown whether they provide Chitons with spatial vision [3]. It is also unclear whether Chiton lenses are made from proteins, like nearly all biological lenses, or from some other material [4]. Electron probe X-ray microanalysis and X-ray diffraction revealed that the Chiton Acanthopleura granulata has the first aragonite lenses ever discovered. We found that these lenses allowA.granulata’s ocellito functionassmallcamera eyes with an angular resolution of about 9–12. Animals responded to the sudden appearance of black, overhead circles with an angular size of 9, but not to equivalent, uniform decreases in the downwelling irradiance. Our behavioral estimates of angular resolution were consistent with estimates derived from focal length and receptor spacing within the A. granulata eye. Behavioral trials further indicated that A. granulata’s eyes provide the same angular resolution in both air and water. We propose that one of the two refractive indices of the birefringent Chiton lens places a focused image on the retina in air, whereas the other does so in water.
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the iron responsive genome of the Chiton acanthopleura granulata
bioRxiv, 2020Co-Authors: Rebecca M Varney, Daniel I Speiser, Carmel Mcdougall, Bernard M Degnan, Kevin M KocotAbstract:Molluscs biomineralize structures that vary in composition, form, and function, prompting questions about the genetic mechanisms responsible for their production and the evolution of these mechanisms. Chitons (Mollusca, Polyplacophora) are a promising system for studies of biomineralization because they build a range of calcified structures including shell plates and spine- or scale-like sclerites. Chitons also harden the teeth of their rasp-like radula with a coat of iron. Here we present the genome of the West Indian fuzzy Chiton Acanthopleura granulata, the first from any aculiferan mollusc. The A. granulata genome has features that may be specialized for iron biomineralization, including a high proportion of genes regulated directly by iron and two isoforms of ferritin, one iron-regulated and the other constitutively translated. The A. granulata genome also contains homologs of many biomineralization genes identified previously in conchiferan molluscs, suggesting the ancestral mollusc had a diverse genetic toolkit for biomineralization.
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evidence for spatial vision in Chiton tuberculatus a Chiton with eyespots
The Journal of Experimental Biology, 2018Co-Authors: Alexandra C N Kingston, Daniel R Chappell, Daniel I SpeiserAbstract:To better understand relationships between the structures and functions of the distributed visual systems of Chitons, we are comparing how morphological differences between the light-sensing structures of these animals relate to their visually-guided behaviors. All Chitons have sensory organs – termed aesthetes – embedded within their protective shell plates. In some species, the aesthetes are interspersed with small, image-forming eyes. In other species, the aesthetes are paired with pigmented eyespots. Previously, we compared the visually-influenced behaviors of Chitons with aesthetes to those of Chitons with both aesthetes and eyes. Here, we characterize the visually-influenced behaviors of Chitons with aesthetes and eyespots. We find that Chitons with eyespots engage in behaviors consistent with spatial vision, but appear to use spatial vision for different tasks than Chitons with eyes. Unlike Chitons with eyes, Chiton tuberculatus and C. marmoratus fail to distinguish between sudden appearances of overhead objects and equivalent, uniform changes in light levels. We also find that C. tuberculatus orients to static objects with angular sizes as small as 10°. Thus, C. tuberculatus demonstrates spatial resolution that is at least as fine as that demonstrated by Chitons with eyes. The eyespots of Chiton are smaller and more numerous than the eyes found in other Chitons and they are separated by angles of Chiton may be more accurately predicted by the network properties of their distributed visual system than by the structural properties of their individual light-detecting organs.
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Evidence for spatial vision in Chiton tuberculatus, a Chiton with eyespots.
The Journal of experimental biology, 2018Co-Authors: Alexandra C N Kingston, Daniel R Chappell, Daniel I SpeiserAbstract:To better understand relationships between the structures and functions of the distributed visual systems of Chitons, we compare how morphological differences between the light-sensing structures of these animals relate to their visually guided behaviors. All Chitons have sensory organs - termed aesthetes - embedded within their protective shell plates. In some species, the aesthetes are interspersed with small, image-forming eyes. In other species, the aesthetes are paired with pigmented eyespots. Previously, we compared the visually influenced behaviors of Chitons with aesthetes to those of Chitons with both aesthetes and eyes. Here, we characterize the visually influenced behaviors of Chitons with aesthetes and eyespots. We find that Chitons with eyespots engage in behaviors consistent with spatial vision, but appear to use spatial vision for different tasks than Chitons with eyes. Unlike Chitons with eyes, Chiton tuberculatus and C. marmoratus fail to distinguish between sudden appearances of overhead objects and equivalent, uniform changes in light levels. We also find that C. tuberculatus orients to static objects with angular sizes as small as 10 deg. Thus, C. tuberculatus demonstrates spatial resolution that is at least as fine as that demonstrated by Chitons with eyes. The eyespots of Chiton are smaller and more numerous than the eyes found in other Chitons and they are separated by angles of
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the shell eyes of the Chiton acanthopleura granulata mollusca polyplacophora use pheomelanin as a screening pigment
Journal of Natural History, 2014Co-Authors: Daniel I Speiser, Daniel G Demartini, Todd H OakleyAbstract:Certain species of Chiton (Mollusca, Polyplacophora) have hundreds of small (< 100 µm) eyes embedded in their dorsal shell plates. These eyes each contain a retina, a layer of screening pigment, and a lens. Previously, we demonstrated that the eyes of Chitons provide spatial vision. As in other camera-type eyes, the screening pigments in the eyes of Chitons absorb off-axis light in order to preserve the contrast of images formed on the retina. Our results indicate that the red-brown, alkali-soluble screening pigment associated with the eyes of the Chiton Acanthopleura granulata (Gmelin, 1791) is pheomelanin. Using high-performance liquid chromatography (HPLC) and MALDI-TOF mass spectroscopy, we find that degrading A. granulata’s screening pigment with alkaline hydrogen peroxide produces 6-(2-amino-2-carboxyethyl)-2-carboxy-4-hydroxybenzothiazole (BTCA), a diagnostic marker of pheomelanin. Chitons are the first molluscs demonstrated to use pheomelanin as a screening pigment in their eyes. Our results sugge...
David Kisailus - One of the best experts on this subject based on the ideXlab platform.
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Integrated transcriptomic and proteomic analyses of a molecular mechanism of radular teeth biomineralization in CryptoChiton stelleri
Scientific Reports, 2019Co-Authors: Michiko Nemoto, Steven Herrera, Takashi Tamura, Kenji Inagaki, David KisailusAbstract:Many species of Chiton are known to deposit magnetite (Fe_3O_4) within the cusps of their heavily mineralized and ultrahard radular teeth. Recently, much attention has been paid to the ultrastructural design and superior mechanical properties of these radular teeth, providing a promising model for the development of novel abrasion resistant materials. Here, we constructed de novo assembled transcripts from the radular tissue of C. stelleri that were used for transcriptome and proteome analysis. Transcriptomic analysis revealed that the top 20 most highly expressed transcripts in the non-mineralized teeth region include the transcripts encoding ferritin, while those in the mineralized teeth region contain a high proportion of mitochondrial respiratory chain proteins. Proteomic analysis identified 22 proteins that were specifically expressed in the mineralized cusp. These specific proteins include a novel protein that we term radular teeth matrix protein1 (RTMP1), globins, peroxidasins, antioxidant enzymes and a ferroxidase protein. This study reports the first de novo transcriptome assembly from C. stelleri , providing a broad overview of radular teeth mineralization. This new transcriptomic resource and the proteomic profiles of mineralized cusp are valuable for further investigation of the molecular mechanisms of radular teeth mineralization in Chitons.
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structural and proteomic analyses of iron oxide biomineralization in Chiton teeth
2018Co-Authors: David Kisailus, Michiko NemotoAbstract:The denticle caps of Chiton teeth exhibit the largest hardness and stiffness among any biological minerals in the world. They consist of a composite structure of highly oriented crystalline nanorods of magnetite surrounded by a veneer of organic. The ultrahard teeth of the Chiton are the first reported example of biologically formed magnetite, and its formation mechanisms have been of great interest to researchers for decades. Recently, using modern nanomechanical characterization techniques, it was shown that Chiton teeth exhibit the largest hardness and stiffness of any biological mineral. The predicted abrasion resistance of Chiton teeth against a blunt contact was reported to be even higher than that of zirconia. Therefore, the elucidation of Chiton teeth synthetic processes could help us learn how to develop novel abrasion-resistant materials and environmentally benign processes for the production of iron oxides and other nanostructured materials. In order to understand the Chiton teeth formation, proteomic analyses of tooth proteins as well as detailed structural analyses of mature and developing teeth were conducted. Based on the results obtained from these analyses, we discuss the underlying mechanisms of iron oxide biomineralization in Chiton teeth.
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Stress and damage mitigation from oriented nanostructures within the radular teeth of cryptoChiton stelleri
Advanced Functional Materials, 2014Co-Authors: Lessa Kay Grunenfelder, Enrique Escobar De Obaldia, Brian Weden, P. Zavattieri, C. Salinas, Qianqian Wang, Richard Wuhrer, Dongsheng Li, David KisailusAbstract:Chiton are marine mollusks who use heavily mineralized and ultrahard teeth to feed on epilithic and endolithic algae on intertidal rocks. To fulfill this function, Chiton teeth must be tough and wear-resistant. Impressive mechanical properties are achieved in the Chiton tooth through a hierarchically arranged composite structure consisting of a hard shell of organic-encased and highly oriented nanostructured magnetite rods that surround a soft core of organic-rich iron phosphate. Microscopic and spectroscopic analyses combined with finite element simulations are used to probe the ultrastructural features and uncover structure–mechanical property relationships in the fully mineralized teeth of the gumboot Chiton CryptoChiton stelleri. By understanding the effects of the nanostructured architecture within the Chiton tooth, abrasion-resistant materials can be developed for tooling and machining applications, as well as coatings for equipment and medical implants.
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proteomic analysis from the mineralized radular teeth of the giant pacific Chiton cryptoChiton stelleri mollusca
Proteomics, 2012Co-Authors: Dongsheng Li, Qianqian Wang, Michiko Nemoto, Tadashi Matsunaga, David KisailusAbstract:The biomineralized radular teeth of Chitons are known to consist of iron-based magnetic crystals, associated with the maximum hardness and stiffness of any biomineral. Based on our transmission electron microscopy analysis of partially mineralized teeth, we suggest that the organic matrix within the teeth controls the iron oxide nucleation. Thus, we used Nano-LC-MS to perform a proteomic analysis of the organic matrix in radular teeth of the Chiton CryptoChiton stelleri in order to identify the proteins involved in the biomineralization process. Since the genome sequence of C. stelleri is not available, cross-species similarity searching and de novo peptide sequencing were used to screen the proteins. Our results indicate that several proteins were dominant in the mineralized part of the radular teeth, amongst which, myoglobin and a highly acidic peptide were identified as possibly involved in the biomineralization process.
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analysis of an ultra hard magnetic biomineral in Chiton radular teeth
Materials Today, 2010Co-Authors: James C. Weaver, Qianqian Wang, Ali Miserez, Anthony Tantuccio, Ryan Stromberg, Krassimir N Bozhilov, Peter T Maxwell, Shinobu T Heier, Elaine Dimasi, David KisailusAbstract:Recent analyses of the ultrastructural and mechanical properties of mineralized biological materials have demonstrated some common architectural features that can help explain their observed damage tolerance. Nature has accomplished this feat through the precise control of anisotropic crystal nucleation and growth processes in conjunction with nanoscale control over the self-assembly of spatially distinct organic and inorganic phases, resulting in effective inhibition of crack propagation through these materials. One such example is found in the hyper-mineralized and abrasion resistant radular teeth of the Chitons, a group of herbivorous marine mollusks who have the surprising capacity to erode away the rocky substrates on which they graze 1-4 . Through the use of modern microscopy and nanomechanical characterization techniques, we describe the architectural and mechanical properties of the radular teeth from CryptoChiton stelleri. Chiton teeth are shown to exhibit the largest hardness and stiffness of any biominerals reported to date, being notably as much as three-fold harder than human enamel and the calcium carbonate-based shells of mollusks. We explain how the unique multi-phasic design of these materials contributes not only to their functionality, but also highlights some interesting design principles that might be applied to the fabrication of synthetic composites.
Julia D. Sigwart - One of the best experts on this subject based on the ideXlab platform.
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HIDDEN BIODIVERSITY: ChitonS IN IRELAND
2020Co-Authors: Julia D. SigwartAbstract:This paper presents the first checklist of Irish polyplacophoran molluscs, including confirmed records for twelve species in the class. The polyplacophorans, or Chitons, are distinctive marine invertebrates found on rocky shores around Ireland. Very little is known about the species diversity or evolutionary relationships among Irish Chitons, or even the class in general. Some baseline data is available for the distribution of these animals around Ireland, but their reactions to potential disturbances such as pollution or climate change are completely unknown, although as elements that are relatively rare in marine intertidal ecosystems, they are thought to be sensitive to disturbances. However, these molluscs are usually overlooked as ‘difficult’ in ecosystem surveys, as they are almost impossible to distinguish without dissection. Consequently, species lists and surveys of marine invertebrates often refer only to the erroneous ‘Chiton sp.’ (a genus so far unrecorded from Ireland) or similar, and indeed there has never previously been an attempt to compile a complete list of the species found in Ireland.
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a new deep water Chiton mollusca polyplacophora from hydrothermal vent ecosystems in the okinawa trough japan
Zootaxa, 2018Co-Authors: Julia D. Sigwart, Chong ChenAbstract:Recent expeditions exploring deep-sea hydrothermal vent ecosystems in the Okinawa Trough, East China Sea resulted in the collection of a hitherto undescribed species of polyplacophoran mollusc found living at three different vent fields at depths of 950–1178 m. This new Chiton is a member of the small lepidopleuran family ProtoChitonidae and is morphologically similar to Hanleyella japonica Saito, 1997. The two species differ in small morphological differences of the valve shape and elevation, are divergent in the standard molecular barcoding mitochondrial gene cytochrome oxidase I (COI), and furthermore the known distribution range of H. japonica is considerably more northern and also shallower. The new species is described herein as Hanleyella henrici n. sp. Additional in situ observations taken in the course of collecting material for this study indicates that Chitons are more abundant in the vicinity of hydrothermal vents than was previously appreciated, and perhaps more speciose.
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Comparative allometric variation in intertidal Chitons (Polyplacophora: Chitonidae)
Zoomorphology, 2018Co-Authors: Christian M. Ibáñez, Roger D. Sepúlveda, Julia D. SigwartAbstract:Allometry involves the study of the relationship between size and shape of an individual, and in particular, the manner in which shape depends on size. Animals with multi-element skeletons may have differing growth allometries in different parts of the body. Chitons, for example, have eight overlapping shell plates or valves of three distinct types: head (one plate), intermediate (six plates), and tail (one plate). The overall Chiton body is ellipsoidal and different species differ in their eccentricity. The aim of this study was to examine overall allometry in size and shape over adult ontogeny, and how these patterns vary among four closely related species of intertidal Chitons from Southeastern Pacific Ocean. For each specimen ( n = 407), measurements were taken of total body length and the exposed anterio-posterior lengths of the eight shell plates. Multivariate allometry was evaluated by means of a principal component analysis for each species separately, and for the total. The results showed differential allometric growth of specific skeletal elements, which varied among species; however, there was no clear evidence for specific differentiable growth stages. The overall trend among the combined species was for weakly positive allometry of shell plate widths, but isometric growth of total length and width; thus, the lateral proportion of the animal occupied by shell increases over growth and conversely “thinner looking” girdles may be generally indicative of older animals.
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Functional morphology in Chitons (Mollusca, Polyplacophora): influences of environment and ocean acidification
Marine Biology, 2015Co-Authors: Julia D. Sigwart, Patrick A. Green, Stephanie B. CroftsAbstract:Polyplacophoran molluscs show low morphological diversity compared to other marine invertebrate clades, yet Chitons are ecologically important grazers that occupy a range of distinct ecological niches. We investigated a potential functional correlate of niche separation in three species of co-occurring mopallid Chitons that have total ranges across differing environments (Mopalia muscosa, Mopalia lignosa, Katharina tunicata). We found that the force needed to fracture the protective valves varied significantly among species. K. tunicata, whose valves have a relatively reduced exposed dorsal surface, was significantly more resistant to fracture than the two Mopalia species (mean force: K. tunicata = 31.9 ± 4.5 N; M. lignosa = 12.5 ± 0.8 N; M. muscosa = 20.2 ± 0.8 N). In Mopalia spp., the terminal valves were significantly stronger than intermediate valves (i.e. higher force to fracture), whereas all valves in K. tunicata appeared to be functionally equivalent. To assess whether future chemical changes predicted under ocean acidification (OA) will affect these species differently, we measured the force to fracture of valves after 10 days of exposure to elevated pCO2 (control = 8.0 pH [407 ± 104, pCO2], elevated = 7.5 pH [1544 ± 249, pCO2]) for both live animals and dissected individual valves. Although previous experimental OA work found significant impacts of elevated pCO2 on adult mollusc shells over similar timescales, we saw no reduction in total strength related to treatment. Our data demonstrate that diversity in Chiton valve morphology has functional implications and that physical changes in local topology and wave exposure may have stronger impacts on adult Chitons than changes in ocean chemistry under future climate change.
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grazing under experimental hypercapnia and elevated temperature does not affect the radula of a Chiton mollusca polyplacophora lepidopleurida
Marine Environmental Research, 2014Co-Authors: Julia D. Sigwart, Nicholas CareyAbstract:Abstract Chitons (class Polyplacophora) are benthic grazing molluscs with an eight-part aragonitic shell armature. The radula, a serial tooth ribbon that extends internally more than half the length of the body, is mineralised on the active feeding teeth with iron magnetite apparently as an adaptation to constant grazing on rocky substrates. As the anterior feeding teeth are eroded they are shed and replaced with a new row. The efficient mineralisation and function of the radula could hypothetically be affected by changing oceans in two ways: changes in seawater chemistry (pH and pCO2) may impact the biomineralisation pathway, potentially leading to a weaker or altered density of the feeding teeth; rising temperatures could increase activity levels in these ectothermic animals, and higher feeding rates could increase wear on the feeding teeth beyond the animals' ability to synthesise, mineralise, and replace radular rows. We therefore examined the effects of pH and temperature on growth and integrity in the radula of the Chiton LeptoChiton asellus. Our experiment implemented three temperature (∼10, 15, 20 °C) and two pCO2 treatments (∼400 μatm, pH 8.0; ∼2000 μatm, pH 7.5) for six treatment groups. Animals (n = 50) were acclimated to the treatment conditions for a period of 4 weeks. This is sufficient time for growth of ca. 7–9 new tooth rows or 20% turnover of the mineralised portion. There was no significant difference in the number of new (non-mineralised) teeth or total tooth row count in any treatment. Examination of the radulae via SEM revealed no differences in microwear or breakage on the feeding cusps correlating to treatment groups. The shell valves also showed no signs of dissolution. As a lineage, Chitons have survived repeated shifts in Earth’s climate through geological time, and at least their radulae may be robust to future perturbations.
Christine Ortiz - One of the best experts on this subject based on the ideXlab platform.
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three dimensional structure of the shell plate assembly of the Chiton tonicella marmorea and its biomechanical consequences
Journal of Structural Biology, 2012Co-Authors: Matthew J. Connors, Dan Gazit, Clemence Godeffroy, Sergio Araya, Ilan Kallai, Hermann Ehrlich, Mary C Boyce, Christine OrtizAbstract:Abstract This study investigates the three-dimensional structure of the eight plate exoskeletal (shell) assembly of the Chiton Tonicella marmorea. X-ray micro-computed tomography and 3D printing elucidate the mechanism of conformational change from a passive (slightly curved, attached to surface) to a defensive (rolled, detached from surface) state of the plate assembly. The passive and defensive conformations exhibited differences in longitudinal curvature index (0.43 vs. 0.70), average plate-to-plate overlap (∼62% vs. ∼48%), cross-sectional overlap heterogeneity (60–82.5% vs. 0–90%, fourth plate), and plate-to-plate separation distance (100% increase in normalized separation distance between plates 4 and 5), respectively. The plate-to-plate interconnections consist of two rigid plates joined by a compliant, actuating muscle, analogous to a geometrically structured shear lap joint. This work provides an understanding of how T. marmorea achieves the balance between mobility and protection. In the passive state, the morphometry of the plates and plate-to-plate interconnections results in an approximately continuous curvature and constant armor thickness, resulting in limited mobility but maximum protection. In the defensive state, the underlying soft tissues gain protection and the Chiton gains mobility through tidal flow, but regions of vulnerability open dorsally, due to the increase in plate-to-plate separation and decrease in plate-to-plate overlap. Lastly, experiments using optical and scanning electron microscopy, mercury porosimetry, and Fourier-transform infrared spectroscopy explore the microstructure and spatial distribution of the six layers within the intermediate plates, the role of multilayering in resisting predatory attacks, and the detection of chitin as a major component of the intra-plate organic matrix and girdle.
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Three-dimensional structure of the shell plate assembly of the Chiton Tonicella marmorea and its biomechanical consequences
Journal of Structural Biology, 2012Co-Authors: Matthew J. Connors, Dan Gazit, Martin Hog, Clemence Godeffroy, Sergio Araya, Ilan Kallai, Mary Boyce, Hermann Ehrlich, Christine OrtizAbstract:This study investigates the three-dimensional structure of the eight plate exoskeletal (shell) assembly of the Chiton Tonicella marmorea. X-ray micro-computed tomography and 3D printing elucidate the mechanism of conformational change from a passive (slightly curved, attached to surface) to a defensive (rolled, detached from surface) state of the plate assembly. The passive and defensive conformations exhibited differences in longitudinal curvature index (0.43 vs. 0.70), average plate-to-plate overlap (∼62% vs. ∼48%), cross-sectional overlap heterogeneity (60-82.5% vs. 0-90%, fourth plate), and plate-to-plate separation distance (100% increase in normalized separation distance between plates 4 and 5), respectively. The plate-to-plate interconnections consist of two rigid plates joined by a compliant, actuating muscle, analogous to a geometrically structured shear lap joint. This work provides an understanding of how T. marmorea achieves the balance between mobility and protection. In the passive state, the morphometry of the plates and plate-to-plate interconnections results in an approximately continuous curvature and constant armor thickness, resulting in limited mobility but maximum protection. In the defensive state, the underlying soft tissues gain protection and the Chiton gains mobility through tidal flow, but regions of vulnerability open dorsally, due to the increase in plate-to-plate separation and decrease in plate-to-plate overlap. Lastly, experiments using optical and scanning electron microscopy, mercury porosimetry, and Fourier-transform infrared spectroscopy explore the microstructure and spatial distribution of the six layers within the intermediate plates, the role of multilayering in resisting predatory attacks, and the detection of chitin as a major component of the intra-plate organic matrix and girdle. © 2012 Elsevier Inc.
Michiko Nemoto - One of the best experts on this subject based on the ideXlab platform.
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Integrated transcriptomic and proteomic analyses of a molecular mechanism of radular teeth biomineralization in CryptoChiton stelleri
Scientific Reports, 2019Co-Authors: Michiko Nemoto, Steven Herrera, Takashi Tamura, Kenji Inagaki, David KisailusAbstract:Many species of Chiton are known to deposit magnetite (Fe_3O_4) within the cusps of their heavily mineralized and ultrahard radular teeth. Recently, much attention has been paid to the ultrastructural design and superior mechanical properties of these radular teeth, providing a promising model for the development of novel abrasion resistant materials. Here, we constructed de novo assembled transcripts from the radular tissue of C. stelleri that were used for transcriptome and proteome analysis. Transcriptomic analysis revealed that the top 20 most highly expressed transcripts in the non-mineralized teeth region include the transcripts encoding ferritin, while those in the mineralized teeth region contain a high proportion of mitochondrial respiratory chain proteins. Proteomic analysis identified 22 proteins that were specifically expressed in the mineralized cusp. These specific proteins include a novel protein that we term radular teeth matrix protein1 (RTMP1), globins, peroxidasins, antioxidant enzymes and a ferroxidase protein. This study reports the first de novo transcriptome assembly from C. stelleri , providing a broad overview of radular teeth mineralization. This new transcriptomic resource and the proteomic profiles of mineralized cusp are valuable for further investigation of the molecular mechanisms of radular teeth mineralization in Chitons.
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structural and proteomic analyses of iron oxide biomineralization in Chiton teeth
2018Co-Authors: David Kisailus, Michiko NemotoAbstract:The denticle caps of Chiton teeth exhibit the largest hardness and stiffness among any biological minerals in the world. They consist of a composite structure of highly oriented crystalline nanorods of magnetite surrounded by a veneer of organic. The ultrahard teeth of the Chiton are the first reported example of biologically formed magnetite, and its formation mechanisms have been of great interest to researchers for decades. Recently, using modern nanomechanical characterization techniques, it was shown that Chiton teeth exhibit the largest hardness and stiffness of any biological mineral. The predicted abrasion resistance of Chiton teeth against a blunt contact was reported to be even higher than that of zirconia. Therefore, the elucidation of Chiton teeth synthetic processes could help us learn how to develop novel abrasion-resistant materials and environmentally benign processes for the production of iron oxides and other nanostructured materials. In order to understand the Chiton teeth formation, proteomic analyses of tooth proteins as well as detailed structural analyses of mature and developing teeth were conducted. Based on the results obtained from these analyses, we discuss the underlying mechanisms of iron oxide biomineralization in Chiton teeth.
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proteomic analysis from the mineralized radular teeth of the giant pacific Chiton cryptoChiton stelleri mollusca
Proteomics, 2012Co-Authors: Dongsheng Li, Qianqian Wang, Michiko Nemoto, Tadashi Matsunaga, David KisailusAbstract:The biomineralized radular teeth of Chitons are known to consist of iron-based magnetic crystals, associated with the maximum hardness and stiffness of any biomineral. Based on our transmission electron microscopy analysis of partially mineralized teeth, we suggest that the organic matrix within the teeth controls the iron oxide nucleation. Thus, we used Nano-LC-MS to perform a proteomic analysis of the organic matrix in radular teeth of the Chiton CryptoChiton stelleri in order to identify the proteins involved in the biomineralization process. Since the genome sequence of C. stelleri is not available, cross-species similarity searching and de novo peptide sequencing were used to screen the proteins. Our results indicate that several proteins were dominant in the mineralized part of the radular teeth, amongst which, myoglobin and a highly acidic peptide were identified as possibly involved in the biomineralization process.