共查询到20条相似文献，搜索用时 15 毫秒
1.
Gabriel E. Bertolesi Yi N. Song Karen Atkinson‐Leadbeater Jung‐Lynn J. Yang Sarah McFarlane 《Pigment cell & melanoma research》2017,30(4):413-423
Lower vertebrates use rapid light‐regulated changes in skin colour for camouflage (background adaptation) or during circadian variation in irradiance levels. Two neuroendocrine systems, the eye/alpha‐melanocyte‐stimulating hormone (α‐MSH) and the pineal complex/melatonin circuits, regulate the process through their respective dispersion and aggregation of pigment granules (melanosomes) in skin melanophores. During development, Xenopus laevis tadpoles raised on a black background or in the dark perceive less light sensed by the eye and darken in response to increased α‐MSH secretion. As embryogenesis proceeds, the pineal complex/melatonin circuit becomes the dominant regulator in the dark and induces lightening of the skin of larvae. The eye/α‐MSH circuit continues to mediate darkening of embryos on a black background, but we propose the circuit is shut down in complete darkness in part by melatonin acting on receptors expressed by pituitary cells to inhibit the expression of pomc, the precursor of α‐MSH. 相似文献
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Yuya Nasu Hirotaka Kato Ayako Sedohara Shin‐ichiro Nishimatsu Masao Sakai 《Development, growth & differentiation》2014,56(9):640-652
Wnt proteins are thought to bind to their receptors on the cell surfaces of neighboring cells. Wnt8 likely substitutes for the dorsal determinants in Xenopus embryos to dorsalize early embryos via the Wnt/β‐catenin pathway. Here, we show that Wnt8 can dorsalize Xenopus embryos working cell autonomously. Wnt8 mRNA was injected into a cleavage‐stage blastomere, and the subcellular distribution of Wnt8 protein was analyzed. Wnt8 protein was predominantly found in the endoplasmic reticulum (ER) and resided at the periphery of the cells; however, this protein was restricted to the mRNA‐injected cellular region as shown by lineage tracing. A mutant Wnt8 that contained an ER retention signal (Wnt8‐KDEL) could dorsalize Xenopus embryos. Finally, Wnt8‐induced dorsalization occurred only in cells injected with Wnt8 mRNA. These experiments suggest that the Wnt8 protein acts within the cell, likely in the ER or on the cell surface in an autocrine manner for dorsalization. 相似文献
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Yoshihisa Ohata Shinya Matsukawa Yuki Moriyama Tatsuo Michiue Kenta Morimoto Yuka Sato Hiroki Kuroda 《Development, growth & differentiation》2014,56(6):460-468
Chemical reagent Ex‐527 is widely used as a major inhibitor of Sirtuin enzymes, which are a family of highly conserved protein deacetylases and have been linked with caloric restriction and aging by modulating energy metabolism, genomic stability, and stress resistance. However, the extent to which Ex‐527 controls early developmental events of vertebrate embryos remains to be understood. Here, we report an examination of Ex‐527 effects during Xenopus early development, followed by a confirmation of expressions of xSirt1 and xSirt2 in embryonic stages and enhancement of acetylation by Ex‐527. First, we found that reductions in size of neural plate at neurula stages were induced by Ex‐527 treatment. Second, tadpoles with short body length and large edematous swellings in the ventral side were frequently observed. Moreover, Ex‐527‐treated embryos showed severe gastrointestinal malformations in late tadpole stages. Taken together with these results, we conclude that the Sirtuin family start functioning at early embryonic stages and is required for various developmental events. 相似文献
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Shigeru Saito Claire T. Saito Masafumi Nozawa Makoto Tominaga 《Molecular ecology》2019,28(15):3561-3571
Ambient temperature fluctuations are detected via the thermosensory system which allows animals to seek preferable thermal conditions or escape from harmful temperatures. Evolutionary changes in thermal perception have thus potentially played crucial roles in niche selection. The genus Xenopus (clawed frog) is suitable for investigating the relationship between thermal perception and niche selection due to their diverse latitudinal and altitudinal distributions. Here we performed comparative analyses of the neuronal heat sensors TRPV1 and TRPA1 among closely related Xenopus species (X. borealis, X. muelleri, X. laevis, and X. tropicalis) to elucidate their functional evolution and to assess whether their functional differences correlate with thermal niche selection among the species. Comparison of TRPV1 among four extant Xenopus species and reconstruction of the ancestral TRPV1 revealed that TRPV1 responses to repeated heat stimulation were specifically altered in the lineage leading to X. tropicalis which inhabits warmer niches. Moreover, the thermal sensitivity of TRPA1 was lower in X. tropicalis than the other species, although the thermal sensitivity of TRPV1 and TRPA1 was not always lower in species that inhabit warmer niches than the species inhabit cooler niches. However, a clear correlation was found in species differences in TRPA1 activity. Heat‐evoked activity of TRPA1 in X. borealis and X. laevis, which are adapted to cooler niches, was significantly higher than in X. tropicalis and X. muelleri which are adapted to warmer niches. These findings suggest that the functional properties of heat sensors changed during Xenopus evolution, potentially altering the preferred temperature ranges among species. 相似文献
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Brigitte Korte Walter Knöchel Stephan A. Wacker 《Development, growth & differentiation》2012,54(7):702-716
POU‐V class proteins like Oct4 are crucial for keeping cells in an undifferentiated state. An Oct4 homologue in Xenopus laevis, Oct25, peaks in expression during early gastrulation, when many cells are still uncommitted. Nevertheless, extensive morphogenesis is taking place in all germ layers at that time. Phenotypical analysis of embryos with Oct25 overexpression revealed morphogenesis defects, beginning during early gastrulation and resulting in spina‐bifida‐like axial defects. Analysis of marker genes and different morphogenesis assays show inhibitory effects on convergence and extension and on mesoderm internalization. On a cellular level, cell–cell adhesion is reduced. On a molecular level, Oct25 overexpression activates expression of PAPC, a functional inhibitor of the cell adhesion molecule EP/C‐cadherin. Intriguingly, Oct25 effects on cell–cell adhesion can be restored by overexpression of EP/C‐cadherin or by inhibition of the PAPC function. Thus, Oct25 affects morphogenesis via activation of PAPC expression and subsequent functional inhibition of EP/C‐cadherin. 相似文献
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Larval to adult microvascular anatomy of the esophagus was studied in the South African Clawed Toad, Xenopus laevis (Daudin) by scanning electron microscopy of vascular corrosion casts and correlative light microscopy of paraplast embedded stained tissue sections. Analyses of vascular corrosion casts of tadpole esophaguses at premetamorphosis revealed a wide‐meshed, but mature looking capillary bed which during following prometamorphosis increased in density and gained the adult‐like pattern during late metamorphic climax by sprouting and nonsprouting angiogenesis. In adult Xenopus, the esophageal mucosa possessed a dense subepithelial capillary bed fed by one or two esophageal arteries that originated from right and/or left thoracic aorta just distal to the origin of the subclavian arteries. In the adult undistended esophagus, esophageal arteries revealed an undulating course, a pattern that guarantees a continuous blood supply when the esophagus is extremely wide expanded as it is the case when adult Xenopus swallows large prey. 相似文献
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Limb regeneration ability, which can be observed in amphibians, has been investigated as a representative phenomenon of organ regeneration. Recently, an alternative experimental system called the accessory limb model was developed to investigate early regulation of amphibian limb regeneration. The accessory limb model contributed to identification of limb regeneration inducers in urodele amphibians. Furthermore, the accessory limb model may be applied to other species to explore universality of regeneration mechanisms. This review aims to connect the insights recently gained to emboss universality of regeneration mechanisms among species. The defined molecules (BMP7 (or2) + FGF2 + FGF8) can transform skin wound healing to organ (limb) regeneration responses. The same molecules can initiate regeneration responses in some species. 相似文献
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Gabriel E. Bertolesi Sherene T. Vazhappilly Carrie L. Hehr Sarah McFarlane 《Pigment cell & melanoma research》2016,29(2):186-198
Light‐regulated skin colour change is an important physiological process in invertebrates and lower vertebrates, and includes daily circadian variation and camouflage (i.e. background adaptation). The photoactivation of melanopsin‐expressing retinal ganglion cells (mRGCs) in the eye initiates an uncharacterized neuroendocrine circuit that regulates melanin dispersion/aggregation through the secretion of alpha‐melanocyte‐stimulating hormone (α‐MSH). We developed experimental models of normal or enucleated Xenopus embryos, as well as in situ cultures of skin of isolated dorsal head and tails, to analyse pharmacological induction of skin pigmentation and α‐MSH synthesis. Both processes are triggered by a melanopsin inhibitor, AA92593, as well as chloride channel modulators. The AA9253 effect is eye‐dependent, while functional data in vivo point to GABAA receptors expressed on pituitary melanotrope cells as the chloride channel blocker target. Based on the pharmacological data, we suggest a neuroendocrine circuit linking mRGCs with α‐MSH secretion, which is used normally during background adaptation. 相似文献
11.
Kohei Terayama Kensuke Kataoka Keisuke Morichika Hidefumi Orii Kenji Watanabe Makoto Mochii 《Development, growth & differentiation》2013,55(2):217-228
Primordial germ cells (PGCs) arise in the early embryo and migrate toward the future gonad through species‐specific pathways. They are assumed to change their migration properties dependent on their own genetic program and/or environmental cues, though information concerning the developmental change in PGC motility is limited. First, we re‐examined the distribution of PGCs in the endodermal region of Xenopus embryos at various stages by using an antibody against Xenopus Daz‐like protein, and found four stages of migration, namely clustering, dispersing, directionally migrating and re‐aggregating. Next, we isolated living PGCs at each stage and directly examined their morphology and locomotive activity in cell cultures. PGCs at the clustering stage were round in shape with small blebs and showed little motility. PGCs in both the dispersing and the directionally migrating stages alternated between the locomotive phase with an elongated morphology and the pausing phase with a rugged morphology. The locomotive activity of the elongated PGCs was accompanied by the persistent formation of a large bleb at the leading front. The duration of the locomotive phase was shortened gradually with the transition from the dispersing stage to the directionally migrating stage. At the re‐aggregating stage, PGCs became round in shape and showed no motility. Thus, we directly showed that the locomotive activity of PGCs changes dynamically depending upon the migrating stage. We also showed that the locomotion and blebbing of the PGCs required F‐actin, myosin II activity and RhoA/Rho‐associated protein kinase (ROCK) signaling. 相似文献
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Gabriel E. Bertolesi Carrie L. Hehr Hayden Munn Sarah McFarlane 《Pigment cell & melanoma research》2016,29(6):688-701
Two biological processes regulate light‐induced skin colour change. A fast ‘physiological pigmentation change’ (i.e. circadian variations or camouflage) involves alterations in the distribution of pigment containing granules in the cytoplasm of chromatophores, while a slower ‘morphological pigmentation change’ (i.e. seasonal variations) entails changes in the number of pigment cells or pigment type. Although linked processes, the neuroendocrine coordination triggering each response remains largely obscure. By evaluating both events in Xenopus laevis embryos, we show that morphological pigmentation initiates by inhibiting the activity of the classical retinal ganglion cells. Morphological pigmentation is always accompanied by physiological pigmentation, and a melatonin receptor antagonist prevents both responses. Physiological pigmentation also initiates in the eye, but with repression of melanopsin‐expressing retinal ganglion cell activity that leads to secretion of alpha‐melanocyte‐stimulating hormone (α‐MSH). Our findings suggest a model in which eye photoperception links physiological and morphological pigmentation by altering α‐MSH and melatonin production, respectively. 相似文献
15.
Narudo Kawai Ikuko Omori Ritsu Kuraishi Hiroyuki Kaneko 《Development, growth & differentiation》2017,59(3):129-140
Reconstruction of a starfish embryo provides unique morphogenesis during the developmental process that is not observed in normal development. Here, we established a novel method for reconstruction from single embryos/larvae. By using this method, we investigated the morphogenetic capabilities in critical steps during the reconstruction process as showed by the reconstructed embryos generated from embryos/larvae at the six developmental stages, or from segregated ectodermal and/or endomesodermal cells. Additionally, the novel method addressed several problems found in prior methods related to reproducibly generating reconstructed embryos. In the reconstructions from the various stage embryos/larvae, the morphogenetic capabilities were substantively reduced in the reconstructed embryos generated from 3‐day bipinnaria (3dBp). The combination experiments using ectodermal or endomesodermal cells segregated from 2dBp or 3dBp showed a reduction of the morphogenetic capabilities in both cells types in 3dBp. The reconstructed embryos generated from ectodermal or endomesodermal cells segregated from 2dBp possessed partial morphological features, such as formation of the epithelium or blastopore, but all failed to develop into bipinnariae. These results indicate two limitations of the morphogenetic capabilities during the reconstruction process. Firstly, the morphogenetic capabilities to reconstruct an embryo are considerably reduced between 2dBp and 3dBp. Secondly, cells specified as ectoderm or endomesoderm possess limited morphogenetic capabilities to reconstruct bipinnaria. Furthermore, our results demonstrate that the interaction between these specified cell types is required for reconstruction. 相似文献
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M. Baucher J. Moussawi O. M. Vandeputte D. Monteyne A. Mol D. Pérez‐Morga M. El Jaziri 《Plant biology (Stuttgart, Germany)》2013,15(5):892-898
The MIR396 family, composed of ath‐miR396a and ath‐miR396b in Arabidopsis, is conserved among plant species and is known to target the Growth‐Regulating Factor (GRF) gene family. ath‐miR396 overexpressors or grf mutants are characterised by small and narrow leaves and show embryogenic defects such as cotyledon fusion. Heterologous expression of ath‐miR396a has been reported in tobacco and resulted in reduction of the expression of three NtGRF genes. In this study, the precursor of the Populus trichocarpa ptc‐miR396c, with a mature sequence identical to ath‐miR396b, was expressed under control of the CaMV35S promoter in tobacco. Typical phenotypes of GRF down‐regulation were observed, including cotyledon fusion and lack of shoot apical meristem (SAM). At later stage of growth, transgenic plants had delayed development and altered specification of organ type during flower development. The third and fourth whorls of floral organs were modified into stigmatoid anthers and fasciated carpels, respectively. Several NtGRF genes containing a miR396 binding site were found to be down‐regulated, and the cleavage of their corresponding mRNA at the miR396 binding site was confirmed for two of them using RACE‐PCR analysis. The data obtained agree with the functional conservation of the miR396 family in plants and suggest a role for the miR396/GRF network in determination of floral organ specification. 相似文献
17.
Thomas C. Wagner Johanna Richter David F. Joubert Christina Fischer 《Ecology and evolution》2018,8(13):6779-6787
The characteristic vegetation structure of arid savannas with a dominant layer of perennial grass is maintained by the putative competitive superiority of the C4 grasses. When this competitive balance is disturbed by weakening the grasses or favoring the recruitment of other species, trees, shrubs, single grass, or forb species can increase and initiate sudden dominance shifts. Such shifts involving woody species, often termed “shrub encroachment”, or the mass spreading of so‐called increaser species have been extensively researched, but studies on similar processes without obvious preceding disturbance are rare. In Namibia, the native herbaceous legume Crotalaria podocarpa has recently encroached parts of the escarpment region, seriously affecting the productivity of local fodder grasses. Here, we studied the interaction between seedlings of the legume and the dominant local fodder grass (Stipagrostis ciliata). We used a pot experiment to test seedling survival and to investigate the growth of Crotalaria in competition with Stipagrostis. Additional field observations were conducted to quantify the interactive effect. We found germination and growth of the legume seedlings to be facilitated by inactive (dead or dormant) grass tussocks and unhindered by active ones. Seedling survival was three times higher in inactive tussocks and Crotalaria grew taller. In the field, high densities of the legume had a clear negative effect on productivity of the grass. The C4 grass was unable to limit the recruitment and spread of the legume, and Crotalaria did outcompete the putative more competitive grass. Hence, the legume is able to spread and establish itself in large numbers and initiate a dominance shift in savannas, similar to shrub encroachment. 相似文献
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D. I. Ojeda R. Jaén‐Molina A. Santos‐Guerra J. Caujape‐Castells Q. Cronk 《Plant biology (Stuttgart, Germany)》2017,19(3):420-427
- In the generally bee‐pollinated genus Lotus a group of four species have evolved bird‐pollinated flowers. The floral changes in these species include altered petal orientation, shape and texture. In Lotus these characters are associated with dorsiventral petal identity, suggesting that shifts in the expression of dorsal identity genes may be involved in the evolution of bird pollination. Of particular interest is Lotus japonicus CYCLOIDEA 2 (LjCYC2), known to determine the presence of papillate conical cells on the dorsal petal in L. japonicus. Bird‐pollinated species are unusual in not having papillate conical cells on the dorsal petal.
- Using RT‐PCR at various stages of flower development, we determined the timing of expression in all petal types for the three putative petal identity genes (CYC‐like genes) in different species with contrasting floral morphology and pollination syndromes.
- In bird‐pollinated species the dorsal identity gene, LjCYC2, is not expressed at the floral stage when papillate conical cells are normally differentiating in bee‐pollinated species. In contrast, in bee‐pollinated species, LjCYC2 is expressed during conical cell development.
- Changes in the timing of expression of the above two genes are associated with modifications in petal growth and lateralisation of the dorsal and ventral petals in the bird‐pollinated species. This study indicates that changes in the timing, rather than spatial distribution, of expression likely contribute to the modifications of petal micromorphology and petal size during the transition from bee to bird pollination in Macaronesian Lotus species.
20.
Sebastian J. Hennige Kathryn J. Coyne Hugh MacIntyre Justin Liefer Mark E. Warner 《Journal of phycology》2013,49(2):349-360
Periodic and seasonal exposure to high light is a common occurrence for many near‐shore and estuarine phytoplankton. Rapid acclimatization to shifts in light may provide an axis by which some species of phytoplankton can outcompete other microalgae. Patterns of photoacclimation and photosynthetic capacity in the raphidophyte Heterosigma akashiwo (Hada) Hada ex Hara et Chihara isolated from the mid‐Atlantic of the United States were followed in continuous cultures at low‐ and high‐light intensities, followed by reciprocal shifts to the opposite light level. The maximum quantum yield (Fv/Fm) as well as the photosynthetic cross‐section (σPSII) of photosystem II was higher in high‐light cultures compared to low‐light cultures. Significant diurnal variability in photochemistry and photoprotection was noted at both light levels, and high‐light‐acclimated cultures displayed greater variability in photoprotective pathways. When shifted from low to high light, there was only a slight and temporary decline in maximum quantum yield, while cell specific growth more than doubled within 24 h. Rapid acclimation to high light was facilitated by short‐term photoprotection (nonphotochemical quenching), reduced PSII reaction center connectivity, and electron transport. Short‐term increases in de‐epoxidated xanthophyll pigments contributed to nonphotochemical protection, but lagged behind initial increases in nonphotochemical quenching and were not the primary pathway of photoprotection in this alga. By 48 h, photochemistry of cultures shifted from low to high light resembled long‐term high‐light‐acclimated cultures. This isolate of H. akashiwo appears well poised to exploit rapid shifts in light by using unique cellular adjustments in light harvesting and photochemistry. 相似文献