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Miyo Terao Morita - One of the best experts on this subject based on the ideXlab platform.
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Micromanipulation of amyloplasts with optical tweezers in Arabidopsis stems
2020Co-Authors: Yoshinori Abe, Miyo Terao Morita, Keisuke Meguriya, Takahisa Matsuzaki, Teruki Sugiyama, Hiroshi Yoshikawa, Masatsugu ToyotaAbstract:AbstractIntracellular sedimentation of highly dense, starch-filled amyloplasts toward the Gravity vector is likely a key initial step for Gravity Sensing in plants. However, recent live-cell imaging technology revealed that most amyloplasts continuously exhibit dynamic, saltatory movements in the endodermal cells of Arabidopsis stems. These complicated movements led to questions about what type of amyloplast movement triggers Gravity Sensing. Here we show that a confocal microscope equipped with optical tweezers can be a powerful tool to trap and manipulate amyloplasts noninvasively, while simultaneously observing cellular responses such as vacuolar dynamics in living cells. A near-infrared (λ = 1064 nm) laser that was focused into the endodermal cells at 1 mW of laser power attracted and captured amyloplasts at the laser focus. The optical force exerted on the amyloplasts was theoretically estimated to be up to 1 pN. Interestingly, endosomes and trans-Golgi networks were trapped at 30 mW but not at 1 mW, which is probably due to lower refractive indices of these organelles than that of the amyloplasts. Because amyloplasts are in close proximity to vacuolar membranes in endodermal cells, their physical interaction could be visualized in real time. The vacuolar membranes drastically stretched and deformed in response to the manipulated movements of amyloplasts by optical tweezers. Our new method provides deep insights into the biophysical properties of plant organelles in vivo and opens a new avenue for studying Gravity-Sensing mechanisms in plants.
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Gravity Sensing tissues for gravitropism are required for anti gravitropic phenotypes of lzy multiple mutants in arabidopsis
Plants (Basel Switzerland), 2020Co-Authors: Nozomi Kawamoto, Akiko Mori, Yuta Kanbe, Moritaka Nakamura, Miyo Terao MoritaAbstract:Plant posture is controlled by various environmental cues, such as light, temperature, and Gravity. The overall architecture is determined by the growth angles of lateral organs, such as roots and branches. The branch growth angle affected by Gravity is known as the gravitropic setpoint angle (GSA), and it has been proposed that the GSA is determined by balancing two opposing growth components: gravitropism and anti-gravitropic offset (AGO). The molecular mechanisms underlying gravitropism have been studied extensively, but little is known about the nature of the AGO. Recent studies reported the importance of LAZY1-LIKE (LZY) family genes in the signaling process for gravitropism, such that loss-of-function mutants of LZY family genes resulted in reversed gravitropism, which we term it here as the “anti-gravitropic” phenotype. We assume that this peculiar phenotype manifests as the AGO due to the loss of gravitropism, we characterized the “anti-gravitropic” phenotype of Arabidopsis lzy multiple mutant genetically and physiologically. Our genetic interaction analyses strongly suggested that Gravity-Sensing cells are required for the “anti-gravitropic” phenotype in roots and lateral branches. We also show that starch-filled amyloplasts play a significant role in the “anti-gravitropic” phenotype, especially in the root of the lzy multiple mutant.
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Bridging the gap between amyloplasts and directional auxin transport in plant gravitropism
Current Opinion in Plant Biology, 2019Co-Authors: Moritaka Nakamura, Takeshi Nishimura, Miyo Terao MoritaAbstract:Gravitropism is the directional control of plant organ growth in response to Gravity. Specialized Gravity-Sensing cells contain amyloplasts that can change their position according to the direction of Gravity. Gravity signaling, which is elicited by the relocation of amyloplasts, is a key process that redirects auxin transport from Gravity-Sensing cells to the lower flank of Gravity-responsive organs. Despite the long history of research on plant gravitropism, a molecular detail of Gravity signaling remained unexplained. Recent studies have characterized the Arabidopsis LAZY1 family genes to be key factors of Gravity signaling. Furthermore, studies regarding Arabidopsis AGCVIII kinases have demonstrated the requirement of auxin transporter PIN-FORMED3 (PIN3) phosphorylation in plant gravitropism.
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Gravity Sensing and signal conversion in plant gravitropism
Journal of Experimental Botany, 2019Co-Authors: Moritaka Nakamura, Miyo Terao Morita, Takeshi NishimuraAbstract:Plant organs control their growth orientation in response to Gravity. Within Gravity-Sensing cells, the input (Gravity Sensing) and signal conversion (Gravity signalling) progress sequentially. The cells contain a number of high-density, starch-accumulating amyloplasts, which sense Gravity when they reposition themselves by sedimentation to the bottom of the cell when the plant organ is re-orientated. This triggers the next step of Gravity signalling, when the physical signal generated by the sedimentation of the amyloplasts is converted into a biochemical signal, which redirects auxin transport towards the lower flank of the plant organ. This review focuses on recent advances in our knowledge of the regulatory mechanisms that underlie amyloplast sedimentation and the system by which this is perceived, and on recent progress in characterising the factors that play significant roles in Gravity signalling by which the sedimentation is linked to the regulation of directional auxin transport. Finally, we discuss the contribution of Gravity signalling factors to the mechanisms that control the gravitropic set-point angle.
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transcriptional regulation of pin genes by four lips and myb88 during arabidopsis root gravitropism
Nature Communications, 2015Co-Authors: Hong Zhe Wang, Miyo Terao Morita, Masao Tasaka, Steffen Vanneste, Tom Beeckman, Ke Zhen Yang, Jia Friml, Erich Grotewold, Fred D Sack, Jie LeAbstract:PIN proteins are auxin export carriers that direct intercellular auxin flow and in turn regulate many aspects of plant growth and development including responses to environmental changes. The Arabidopsis R2R3-MYB transcription factor FOUR LIPS (FLP) and its paralogue MYB88 regulate terminal divisions during stomatal development, as well as female reproductive development and stress responses. Here we show that FLP and MYB88 act redundantly but differentially in regulating the transcription of PIN3 and PIN7 in Gravity-Sensing cells of primary and lateral roots. On the one hand, FLP is involved in responses to Gravity stimulation in primary roots, whereas on the other, FLP and MYB88 function complementarily in establishing the gravitropic set-point angles of lateral roots. Our results support a model in which FLP and MYB88 expression specifically determines the temporal-spatial patterns of PIN3 and PIN7 transcription that are closely associated with their preferential functions during root responses to Gravity.
Masao Tasaka - One of the best experts on this subject based on the ideXlab platform.
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transcriptional regulation of pin genes by four lips and myb88 during arabidopsis root gravitropism
Nature Communications, 2015Co-Authors: Hong Zhe Wang, Miyo Terao Morita, Masao Tasaka, Steffen Vanneste, Tom Beeckman, Ke Zhen Yang, Jia Friml, Erich Grotewold, Fred D Sack, Jie LeAbstract:PIN proteins are auxin export carriers that direct intercellular auxin flow and in turn regulate many aspects of plant growth and development including responses to environmental changes. The Arabidopsis R2R3-MYB transcription factor FOUR LIPS (FLP) and its paralogue MYB88 regulate terminal divisions during stomatal development, as well as female reproductive development and stress responses. Here we show that FLP and MYB88 act redundantly but differentially in regulating the transcription of PIN3 and PIN7 in Gravity-Sensing cells of primary and lateral roots. On the one hand, FLP is involved in responses to Gravity stimulation in primary roots, whereas on the other, FLP and MYB88 function complementarily in establishing the gravitropic set-point angles of lateral roots. Our results support a model in which FLP and MYB88 expression specifically determines the temporal-spatial patterns of PIN3 and PIN7 transcription that are closely associated with their preferential functions during root responses to Gravity.
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live cell imaging of cytoskeletal and organelle dynamics in Gravity Sensing cells in plant gravitropism
Methods of Molecular Biology, 2015Co-Authors: Moritaka Nakamura, Masao Tasaka, Masatsugu Toyota, Miyo Terao MoritaAbstract:: Plants sense Gravity and change their morphology/growth direction accordingly (gravitropism). The early process of gravitropism, Gravity Sensing, is supposed to be triggered by sedimentation of starch-filled plastids (amyloplasts) in statocytes such as root columella cells and shoot endodermal cells. For several decades, many scientists have focused on characterizing the role of the amyloplasts and observed their intracellular sedimentation in various plants. Recently, it has been discovered that the complex sedimentary movements of the amyloplasts are created not only by Gravity but also by cytoskeletal/organelle dynamics, such as those of actin filaments and the vacuolar membrane. Thus, to understand how plants sense Gravity, we need to analyze both amyloplast movements and their regulatory systems in statocytes. We have developed a vertical-stage confocal microscope that allows multicolor fluorescence imaging of amyloplasts, actin filaments and vacuolar membranes in vertically oriented plant tissues. We also developed a centrifuge microscope that allows bright-field imaging of amyloplasts during centrifugation. These microscope systems provide new insights into Gravity-Sensing mechanisms in Arabidopsis.
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a unique heat repeat containing protein shoot gravitropism6 is involved in vacuolar membrane dynamics in Gravity Sensing cells of arabidopsis inflorescence stem
Plant and Cell Physiology, 2014Co-Authors: Yasuko Hashiguchi, Takehide Kato, Daisuke Yano, Kiyoshi Nagafusa, Masao Tasaka, Chieko Saito, Akihiko Nakano, Takashi Ueda, Tomohiro Uemura, Miyo Terao MoritaAbstract:Plant vacuoles play critical roles in development, growth and stress responses. In mature cells, vacuolar membranes (VMs) display several types of structures, which are formed by invagination and folding of VMs into the lumenal side and can gradually move and change shape. Although such VM structures are observed in a broad range of tissue types and plant species, the molecular mechanism underlying their formation and maintenance remains unclear. Here, we report that a novel HEAT-repeat protein, SHOOT GRAVITROPISM6 (SGR6), of Arabidopsis is involved in the control of morphological changes and dynamics of VM structures in endodermal cells, which are the Gravity-Sensing cells in shoots. SGR6 is a membrane-associated protein that is mainly localized to the VM in stem endodermal cells. The sgr6 mutant stem exhibits a reduced gravitropic response. Higher plants utilize amyloplast sedimentation as a means to sense Gravity direction. Amyloplasts are surrounded by VMs in Arabidopsis endodermal cells, and the flexible and dynamic structure of VMs is important for amyloplast sedimentation. We demonstrated that such dynamic features of VMs are gradually lost in sgr6 endodermal cells during a 30 min observation period. Histological analysis revealed that amyloplast sedimentation was impaired in sgr6. Detailed live-cell imaging analyses revealed that the VM structures in sgr6 had severe defects in morphological changes and dynamics. Our results suggest that SGR6 is a novel protein involved in the formation and/or maintenance of invaginated VM structures in Gravity-Sensing cells.
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mechanism of higher plant Gravity Sensing
American Journal of Botany, 2013Co-Authors: Yasuko Hashiguchi, Masao Tasaka, Miyo Terao MoritaAbstract:Higher plants have developed statocytes, specialized tissues or cells for Gravity Sensing, and subsequent signal formation. Root and shoot statocytes commonly harbor a number of amyloplasts, and amyloplast sedimentation in the direction of Gravity is a critical process in Gravity Sensing. However, the molecular mechanism underlying amyloplast-dependent Gravity Sensing is largely unknown. In this review, we mainly describe the molecular basis for the Gravity Sensing mechanism, i.e., the molecules and their functions involved in amyloplast sedimentation. Several analyses of statocyte images in living plant organs have implied differences in the regulation of amyloplast movements between root and shoot statocytes. Amyloplasts in shoot statocytes display not only sedimentable but upward, saltatory movements, but the latter are rarely observed in root statocytes. A series of genetic studies on shoot gravitropism mutants of Arabidopsis thaliana has revealed that two intracellular components, the vacuolar membrane (VM) and actin microfilaments (AFs), within the shoot statocyte play important roles in amyloplast dynamics. Flexible VM structures surrounding the amyloplasts seem to allow them to freely sediment toward the bottom of cells. In contrast, long actin cables mediate the saltatory movements of amyloplasts. Thus, amyloplasts in shoot statocytes undergo a dynamic equilibrium of movement, and a proper intracellular environment for statocytes is essential for normal shoot gravitropism. Further analyses to identify the molecular regulators of amyloplast dynamics, including sedimentation, may contribute to an understanding of the Gravity Sensing mechanism in higher plants.
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an arabidopsis e3 ligase shoot gravitropism9 modulates the interaction between statoliths and f actin in Gravity Sensing
The Plant Cell, 2011Co-Authors: Moritaka Nakamura, Masao Tasaka, Masatsugu Toyota, Miyo Terao MoritaAbstract:Higher plants use the sedimentation of amyloplasts in statocytes as statolith to sense the direction of Gravity during gravitropism. In Arabidopsis thaliana inflorescence stem statocyte, amyloplasts are in complex movement; some show jumping-like saltatory movement and some tend to sediment toward the Gravity direction. Here, we report that a RING-type E3 ligase SHOOT GRAVITROPISM9 (SGR9) localized to amyloplasts modulates amyloplast dynamics. In the sgr9 mutant, which exhibits reduced gravitropism, amyloplasts did not sediment but exhibited increased saltatory movement. Amyloplasts sometimes formed a cluster that is abnormally entangled with actin filaments (AFs) in sgr9. By contrast, in the fiz1 mutant, an ACT8 semidominant mutant that induces fragmentation of AFs, amyloplasts, lost saltatory movement and sedimented with nearly statically. Both treatment with Latrunculin B, an inhibitor of AF polymerization, and the fiz1 mutation rescued the gravitropic defect of sgr9. In addition, fiz1 decreased saltatory movement and induced amyloplast sedimentation even in sgr9. Our results suggest that amyloplasts are in equilibrium between sedimentation and saltatory movement in wild-type endodermal cells. Furthermore, this equilibrium is the result of the interaction between amyloplasts and AFs modulated by the SGR9. SGR9 may promote detachment of amyloplasts from AFs, allowing the amyloplasts to sediment in the AFs-dependent equilibrium of amyloplast dynamics.
Patrick Masson - One of the best experts on this subject based on the ideXlab platform.
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gravitropism of plant organs undergoing primary growth
2019Co-Authors: Shihheng Su, Patrick MassonAbstract:As sessile organisms anchored to their substrate, plants have to develop in such a way that their organs can fulfill essential primary functions, which include photosynthesis, gas exchange and reproduction for shoots, and anchoring as well as water and nutrients uptake for roots. To do so, these organs have to use directional information within their environments as growth guides. Gravity, a constant parameter on Earth, is one of the cues used by most organs to direct growth, a process named gravitropism. Typically, shoots will grow against the Gravity vector whereas roots will follow it. Furthermore, lateral organs will grow along shallower vectors relative to Gravity, whose obliqueness is dictated by endogenous/hormonal and environmental cues. In this chapter, we review the molecular mechanisms that allow angiosperm organs to use Gravity as a growth guide. Gravity-Sensing cells named statocytes contain dense starch-filled plastids (amyloplasts) that sediment within their cytoplasm. These cells are located in the columella region of the root cap and in the endodermis that surrounds the vasculature in shoots. Amyloplast sedimentation in these cells promotes a polarization of auxin efflux facilitators to the bottom membrane, creating a downward flow of auxin that results in a lateral gradient across the stimulated organ. Differential auxin accumulation on opposite flanks of the organ results in differential cellular elongation upon transmission to the site of response, a process that is responsible for upward curvature in shoots and downward growth in roots. Lateral organs, on the other hand, respond to similar stimuli by developing weaker lateral auxin gradients, leading to shallower growth angles from Gravity. An abundance of research carried out by multiple laboratories around the world has recently led to important new insights into the mechanisms that govern these complex processes and the machinery that fine-tunes them to ultimately yield highly controlled and amazingly complex responses. This chapter attempts to discuss these mechanisms and identify some of the areas in need of further investigation in this important area of plant biology.
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molecular mechanisms of root gravitropism
Current Biology, 2017Co-Authors: Shihheng Su, Nicole M Gibbs, Amy L Jancewicz, Patrick MassonAbstract:Summary Plant shoots typically grow against the Gravity vector to access light, whereas roots grow downward into the soil to take up water and nutrients. These gravitropic responses can be altered by developmental and environmental cues. In this review, we discuss the molecular mechanisms that govern the gravitropism of angiosperm roots, where a physical separation between sites for Gravity Sensing and curvature response has facilitated discovery. Gravity Sensing takes place in the columella cells of the root cap, where sedimentation of starch-filled plastids (amyloplasts) triggers a pathway that results in a relocalization to the lower side of the cell of PIN proteins, which facilitate efflux of the plant hormone auxin efflux. Consequently, auxin accumulates in the lower half of the root, triggering bending of the root tip at the elongation zone. We review our understanding of the molecular mechanisms that control this process in primary roots, and discuss recent insights into the regulation of oblique growth in lateral roots and its impact on root-system architecture and soil exploration.
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Gravity Sensing and signal transduction in vascular plant primary roots
American Journal of Botany, 2013Co-Authors: Katherine L. Baldwin, Allison K. Strohm, Patrick MassonAbstract:During gravitropism, the potential energy of Gravity is converted into a biochemical signal. How this transfer occurs remains one of the most exciting mysteries in plant cell biology. New experiments are filling in pieces of the puzzle. In this review, we introduce gravitropism and give an overview of what we know about Gravity Sensing in roots of vascular plants, with special highlight on recent papers. When plant roots are reoriented sideways, amyloplast resedimentation in the columella cells is a key initial step in Gravity Sensing. This process somehow leads to cytoplasmic alkalinization of these cells followed by relocalization of auxin efflux carriers (PINs). This changes auxin flow throughout the root, generating a lateral gradient of auxin across the cap that upon transmission to the elongation zone leads to differential cell elongation and gravibending. We will present the evidence for and against the following players having a role in transferring the signal from the amyloplast sedimentation into the auxin signaling cascade: mechanosensitive ion channels, actin, calcium ions, inositol trisphosphate, receptors/ligands, ARG1/ARL2, spermine, and the TOC complex. We also outline auxin transport and signaling during gravitropism.
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arabidopsis thaliana a model for the study of root and shoot gravitropism
The Arabidopsis Book, 2002Co-Authors: Patrick Masson, Miyo Terao Morita, Masao Tasaka, Changhui Guan, Rujin Chen, Kanokporn BoonsirichaiAbstract:Abstract For most plants, shoots grow upward and roots grow downward. These growth patterns illustrate the ability for plant organs to guide their growth at a specified angle from the Gravity vector (gravitropism). They allow shoots to grow upward toward light, where they can photosynthesize, and roots to grow downward into the soil, where they can anchor the plant as well as take up water and mineral ions. Gravitropism involves several steps organized in a specific response pathway. These include the perception of a gravistimulus (reorientation within the Gravity field), the transduction of this mechanical stimulus into a physiological signal, the transmission of this signal from the site of Sensing to the site of response, and a curvature-response which allows the organ tip to resume growth at a predefined set angle from the Gravity vector. The primary sites for Gravity Sensing are located in the cap for roots, and in the endodermis for shoots. The curvature response occurs in the elongation zones for e...
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root gravitropism an experimental tool to investigate basic cellular and molecular processes underlying mechanoSensing and signal transmission in plants
Annual Review of Plant Biology, 2002Co-Authors: Kanokporn Boonsirichai, Changhui Guan, Rujin Chen, Patrick MassonAbstract:▪ Abstract The ability of plant organs to use Gravity as a guide for growth, named gravitropism, has been recognized for over two centuries. This growth response to the environment contributes significantly to the upward growth of shoots and the downward growth of roots commonly observed throughout the plant kingdom. Root gravitropism has received a great deal of attention because there is a physical separation between the primary site for Gravity Sensing, located in the root cap, and the site of differential growth response, located in the elongation zones (EZs). Hence, this system allows identification and characterization of different phases of gravitropism, including Gravity perception, signal transduction, signal transmission, and curvature response. Recent studies support some aspects of an old model for Gravity Sensing, which postulates that root-cap columellar amyloplasts constitute the susceptors for Gravity perception. Such studies have also allowed the identification of several molecules that a...
Jeffrey S Batten - One of the best experts on this subject based on the ideXlab platform.
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the morphogenic features of otoconia during larval development of cynops pyrrhogaster the japanese red bellied newt
Hearing Research, 1995Co-Authors: Peter S Steyger, Michael L Wiederhold, Jeffrey S BattenAbstract:Otoconia are calcified protein matrices within the Gravity-Sensing organs of the vertebrate vestibular system. Mammalian otoconia are barrel-shaped with triplanar facets at each end. Reptilian otoconia are commonly prismatic or fusiform in shape. Amphibians have all three otoconial morphologies, barrel-shaped otoconia within the utricle, with prismatic and fusiform otoconia in the saccule. Scanning electron microscopy revealed a sequential appearance of all three otoconial morphologies during larval development of the newt, Cynops pyrrhogaster. The first otoconia appear within a single, developing otolith, and some resemble adult barrel-shaped otoconia. As the larvae hatch, around stages 39-42, the single otolith divides into two anatomically separate regions, the utricle and saccule, and both contain otoconia similar to those seen in the single otolith. Throughout development, these otoconia may have variable morphologies, with serrated surfaces, or circumferential striations with either separated facets or adjacent facets in the triplanar end-regions. Small fusiform otoconia occur later, at stage 51, and only in the saccule. Prismatic otoconia appear later still, at stage 55, and again only in the saccule. Thus, although prismatic otoconia are the most numerous in adult newts, it is the last vestibular otoconial morphology to be expressed.
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development of the otolith organs and semicircular canals in the japanese red bellied newt cynops pyrrhogaster
Hearing Research, 1995Co-Authors: Michael L Wiederhold, Jeffrey S Batten, Masamichi Yamashita, Kristin A Larsen, Hajime Koike, Makoto AsashimaAbstract:The sequence in which the otoliths and semicircular canals and their associated sensory epithelia appear and develop in the newt are described. Three-dimensional reconstruction of serial sections through the otic vesicle of newt embryos from stages 31 through 58 demonstrate the first appearance, relative position and growth of the otoliths. A single otolith is first seen in stage 33 embryos (approximately 9 days old); this splits into separate utricular and saccular otoliths at stage 40 (13 days). The lateral semicircular canal is the first to appear, at stage 41 (14 days). The anterior and posterior canals appear approximately one week later and the vestibular apparatus is essentially fully formed at stage 58 (approximately 5 weeks). The data reported here will serve as ground-based controls for fertilized newt eggs flown on the International MicroGravity Laboratory-2 Space Shuttle flight, to investigate the influence of microGravity on the development of the Gravity-Sensing organs.
Michael L Wiederhold - One of the best experts on this subject based on the ideXlab platform.
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Experiment Team Principal Investigator: Michael L. Wiederhold Early Development of Gravity- Sensing Organs in MicroGravity Co-Investigators: Wenyuan Gao, Authors
2015Co-Authors: Michael L Wiederhold, Wenyuan Gao, Jeffrey L. Harrison, Kevin A. ParkerAbstract:Most animals have organs that sense Gravity. These organs use dense stones (called otoliths or statoconia), which rest on the sensitive hairs of specialized Gravity- and motion-Sensing cells. The weight of the stones bends the hairs in the direction of gravitational pull. The cells in turn send a coded representation of the grav-ity or motion stimulus to the central nervous system. Previous experiments, in which the eggs or larvae of a marine mollusk (Aplysia californica, the sea hare) were raised on a centrifuge, demonstrated that the size of the stones (or “test mass”) was reduced in a graded manner as the Gravity field was increased. This suggests that some control mechanism was acting to “normalize ” the weight of the stones. The experiments described here were designed to test the hypothesis that, during their initial development, the mass of the stones is regu-lated to achieve a desired weight. If this is the case, we would expect a larger-than-normal otolith would develop in animals reared in the weightlessness of space. To test this, freshwater snails and swordtail fish were studied after spaceflight. The snails mated in space, and the stones (statoconia) in their statocysts developed in microGravity. Pre-mated adult female swordtail fish were flown on the Space Shuttle, and the developing lar-vae were collected after landing. Juvenile fish, where the larval development had taken place on the ground, were also flown. In snails that developed in space, the total volume of statoconia forming the test mass wa
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the morphogenic features of otoconia during larval development of cynops pyrrhogaster the japanese red bellied newt
Hearing Research, 1995Co-Authors: Peter S Steyger, Michael L Wiederhold, Jeffrey S BattenAbstract:Otoconia are calcified protein matrices within the Gravity-Sensing organs of the vertebrate vestibular system. Mammalian otoconia are barrel-shaped with triplanar facets at each end. Reptilian otoconia are commonly prismatic or fusiform in shape. Amphibians have all three otoconial morphologies, barrel-shaped otoconia within the utricle, with prismatic and fusiform otoconia in the saccule. Scanning electron microscopy revealed a sequential appearance of all three otoconial morphologies during larval development of the newt, Cynops pyrrhogaster. The first otoconia appear within a single, developing otolith, and some resemble adult barrel-shaped otoconia. As the larvae hatch, around stages 39-42, the single otolith divides into two anatomically separate regions, the utricle and saccule, and both contain otoconia similar to those seen in the single otolith. Throughout development, these otoconia may have variable morphologies, with serrated surfaces, or circumferential striations with either separated facets or adjacent facets in the triplanar end-regions. Small fusiform otoconia occur later, at stage 51, and only in the saccule. Prismatic otoconia appear later still, at stage 55, and again only in the saccule. Thus, although prismatic otoconia are the most numerous in adult newts, it is the last vestibular otoconial morphology to be expressed.
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development of the otolith organs and semicircular canals in the japanese red bellied newt cynops pyrrhogaster
Hearing Research, 1995Co-Authors: Michael L Wiederhold, Jeffrey S Batten, Masamichi Yamashita, Kristin A Larsen, Hajime Koike, Makoto AsashimaAbstract:The sequence in which the otoliths and semicircular canals and their associated sensory epithelia appear and develop in the newt are described. Three-dimensional reconstruction of serial sections through the otic vesicle of newt embryos from stages 31 through 58 demonstrate the first appearance, relative position and growth of the otoliths. A single otolith is first seen in stage 33 embryos (approximately 9 days old); this splits into separate utricular and saccular otoliths at stage 40 (13 days). The lateral semicircular canal is the first to appear, at stage 41 (14 days). The anterior and posterior canals appear approximately one week later and the vestibular apparatus is essentially fully formed at stage 58 (approximately 5 weeks). The data reported here will serve as ground-based controls for fertilized newt eggs flown on the International MicroGravity Laboratory-2 Space Shuttle flight, to investigate the influence of microGravity on the development of the Gravity-Sensing organs.
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formation of otoconia in the japanese red bellied newt cynops pyrrhogaster
Advances in Space Research, 1994Co-Authors: Michael L Wiederhold, Masamichi Yamashita, K Larsen, Makoto AsashimaAbstract:Pre-mated adult female newts and fertilized eggs will be flown on the International MicroGravity Laboratory-2 flight, in 1994. One objective of the flight will be to observe the influence of microGravity on the development of the Gravity-Sensing organs in the inner ear. These organs contain sensory hair cells covered by a layer of dense stones (otoconia). Gravity and linear acceleration exert forces on these masses, leading to excitation of the nerve fibers innervating the hair cells. If the production of the otoliths is regulated to reach an optimal weight, their development might be abnormal in microGravity. Ground-based control experiments are reported describing the developmental sequence in which both the otoliths and their associated sensory epithelium and the semicircular canals appear and develop. Three-dimensional reconstruction of serial sections through the otic vesicle of newt embryos at stages 31 through 58 demonstrate the first appearance, relative position and growth of the otoliths. Reports of experiments in which fertilized frog eggs were flown on a Russian Cosmos mission conclude that the utricular otolith is increased in volume, whereas the saccular otolith maintains normal size, suggesting that at least in the utricle, the weight of the otolith might be regulated.
