117 research outputs found
GIANT CHLOROPLAST 1 Is Essential for Correct Plastid Division in Arabidopsis
AbstractPlastids are vital plant organelles involved in many essential biological processes [1, 2]. Plastids are not created de novo but divide by binary fission mediated by nuclear-encoded proteins of both prokaryotic and eukaryotic origin [3β7]. Although several plastid division proteins have been identified in plants [8β17], limited information exists regarding possible division control mechanisms. Here, we describe the identification of GIANT CHLOROPLAST 1 (GC1), a new nuclear-encoded protein essential for correct plastid division in Arabidopsis. GC1 is plastid-localized and is anchored to the stromal surface of the chloroplast inner envelope by a C-terminal amphipathic helix. In Arabidopsis, GC1 deficiency results in mesophyll cells harbouring one to two giant chloroplasts, whilst GC1 overexpression has no effect on division. GC1 can form homodimers but does not show any interaction with the Arabidopsis plastid division proteins AtFtsZ1-1, AtFtsZ2-1, AtMinD1, or AtMinE1. Analysis reveals that GC1-deficient giant chloroplasts contain densely packed wild-type-like thylakoid membranes and that GC1-deficient leaves exhibit lower rates of CO2 assimilation compared to wild-type. Although GC1 shows similarity to a putative cyanobacterial SulA cell division inhibitor, our findings suggest that GC1 does not act as a plastid division inhibitor but, rather, as a positive factor at an early stage of the division process
Thermal Infrared Imaging Experiments of C-Type Asteroid 162173 Ryugu on Hayabusa2
The thermal infrared imager TIR onboard Hayabusa2 has been developed to investigate thermo-physical properties of C-type, near-Earth asteroid 162173 Ryugu. TIR is one of the remote science instruments on Hayabusa2 designed to understand the nature of a volatile-rich solar system small body, but it also has significant mission objectives to provide information on surface physical properties and conditions for sampling site selection as well as the assessment of safe landing operations. TIR is based on a two-dimensional uncooled micro-bolometer array inherited from the Longwave Infrared Camera LIR on Akatsuki (Fukuhara et al., 2011). TIR takes images of thermal infrared emission in 8 to 12 ΞΌm with a field of view of 16Γ12β and a spatial resolution of 0.05β per pixel. TIR covers the temperature range from 150 to 460 K, including the well calibrated range from 230 to 420 K. Temperature accuracy is within 2 K or better for summed images, and the relative accuracy or noise equivalent temperature difference (NETD) at each of pixels is 0.4 K or lower for the well-calibrated temperature range. TIR takes a couple of images with shutter open and closed, the corresponding dark frame, and provides a true thermal image by dark frame subtraction. Data processing involves summation of multiple images, image processing including the StarPixel compression (Hihara et al., 2014), and transfer to the data recorder in the spacecraft digital electronics (DE). We report the scientific and mission objectives of TIR, the requirements and constraints for the instrument specifications, the designed instrumentation and the pre-flight and in-flight performances of TIR, as well as its observation plan during the Hayabusa2 mission
Algorithm to determine the outcome of patients with acute liver failure: a data-mining analysis using decision trees
Cyclical and Patch-Like GDNF Distribution along the Basal Surface of Sertoli Cells in Mouse and Hamster Testes
BACKGROUND AND AIMS: In mammalian spermatogenesis, glial cell line-derived neurotrophic factor (GDNF) is one of the major Sertoli cell-derived factors which regulates the maintenance of undifferentiated spermatogonia including spermatogonial stem cells (SSCs) through GDNF family receptor Ξ±1 (GFRΞ±1). It remains unclear as to when, where and how GDNF molecules are produced and exposed to the GFRΞ±1-positive spermatogonia in vivo. METHODOLOGY AND PRINCIPAL FINDINGS: Here we show the cyclical and patch-like distribution of immunoreactive GDNF-positive signals and their close co-localization with a subpopulation of GFRΞ±1-positive spermatogonia along the basal surface of Sertoli cells in mice and hamsters. Anti-GDNF section immunostaining revealed that GDNF-positive signals are mainly cytoplasmic and observed specifically in the Sertoli cells in a species-specific as well as a seminiferous cycle- and spermatogenic activity-dependent manner. In contrast to the ubiquitous GDNF signals in mouse testes, high levels of its signals were cyclically observed in hamster testes prior to spermiation. Whole-mount anti-GDNF staining of the seminiferous tubules successfully visualized the cyclical and patch-like extracellular distribution of GDNF-positive granular deposits along the basal surface of Sertoli cells in both species. Double-staining of GDNF and GFRΞ±1 demonstrated the close co-localization of GDNF deposits and a subpopulation of GFRΞ±1-positive spermatogonia. In both species, GFRΞ±1-positive cells showed a slender bipolar shape as well as a tendency for increased cell numbers in the GDNF-enriched area, as compared with those in the GDNF-low/negative area of the seminiferous tubules. CONCLUSION/SIGNIFICANCE: Our data provide direct evidence of regionally defined patch-like GDNF-positive signal site in which GFRΞ±1-positive spermatogonia possibly interact with GDNF in the basal compartment of the seminiferous tubules
WDR55 Is a Nucleolar Modulator of Ribosomal RNA Synthesis, Cell Cycle Progression, and Teleost Organ Development
The thymus is a vertebrate-specific organ where T lymphocytes are generated. Genetic programs that lead to thymus development are incompletely understood. We previously screened ethylnitrosourea-induced medaka mutants for recessive defects in thymus development. Here we report that one of those mutants is caused by a missense mutation in a gene encoding the previously uncharacterized protein WDR55 carrying the tryptophan-aspartate-repeat motif. We find that WDR55 is a novel nucleolar protein involved in the production of ribosomal RNA (rRNA). Defects in WDR55 cause aberrant accumulation of rRNA intermediates and cell cycle arrest. A mutation in WDR55 in zebrafish also leads to analogous defects in thymus development, whereas WDR55-null mice are lethal before implantation. These results indicate that WDR55 is a nuclear modulator of rRNA synthesis, cell cycle progression, and embryonic organogenesis including teleost thymus development
Fractional anisotropy in the centrum semiovale as a quantitative indicator of cerebral white matter damage in the subacute phase in patients with carbon monoxide poisoning: correlation with the concentration of myelin basic protein in cerebrospinal fluid
Facilitation of axon outgrowth via a Wnt5a-CaMKK-CaMKIΞ± pathway during neuronal polarization
The Arabidopsis minE mutation causes new plastid and FtsZ1 localization phenotypes in the leaf epidermis
Plastids in the leaf epidermal cells of plants are regarded as immature chloroplasts that, like mesophyll chloroplasts, undergo binary fission. While mesophyll chloroplasts have generally been used to study plastid division, recent studies have suggested the presence of tissue- or plastid type-dependent regulation of plastid division. Here, we report the detailed morphology of plastids and their stromules, and the intraplastidic localization of the chloroplast division-related protein AtFtsZ1-1, in the leaf epidermis of an Arabidopsis mutant that harbors a mutation in the chloroplast division site determinant gene AtMinE1. In atminE1, the size and shape of epidermal plastids varied widely, which contrasts with the plastid phenotype observed in atminE1 mesophyll cells. In particular, atminE1 epidermal plastids occasionally displayed grape-like morphology, a novel phenotype induced by a plastid division mutation. Observation of an atminE1 transgenic line harboring an AtMinE1 promoter::AtMinE1-yellow fluorescent protein fusion gene confirmed the expression and plastidic localization of AtMinE1 in the leaf epidermis. Further examination revealed that constriction of plastids and stromules mediated by the FtsZ1 ring contributed to the plastid pleomorphism in the atminE1 epidermis. These results illustrate that a single plastid division mutation can have dramatic consequences for epidermal plastid morphology, thereby implying that plastid division and morphogenesis are differentially regulated in epidermal and mesophyll plastids
The <i>tgd5</i> Mutation Affects Plastid Structure and Causes Giant Lipid Droplet Formation in Trichomes of <i>Arabidopsis</i>
Trichomes, epidermal protrusions in terrestrial plants, play diverse roles in plant defense, metabolism, and development. Arabidopsis thaliana, a model plant with single-celled and non-glandular trichomes, is a valuable system for studying cell differentiation in plants. However, organelle biology in Arabidopsis trichomes is relatively underexplored. Using light and transmission electron microscopy, we investigated the phenotypes of intracellular structures in Arabidopsis trichomes caused by tgd5 mutations, which are known to disrupt lipid transfer from the endoplasmic reticulum to plastids and have a large impact on chloroplast morphology in pavement and guard cells. Significant phenotypic changes in the plastid structure were observed in tgd5 trichome cells, including the absence of plastoglobuli, the emergence of clusters of electron-dense particles in the stroma, and the possibly cup-shaped morphology of plastids. Additionally, the tgd5 mutations triggered the formation of giant, up to 15 Β΅m in diameter, neutral lipid-containing droplets in the trichome cells, as revealed using histochemical staining with lipophilic dyes. These lipid droplets were substantially larger and more frequent in trichome cells than in other types of cells in tgd5. These findings highlight the role of TGD5 in maintaining plastid structure and implicate the unique activity of lipid metabolism in Arabidopsis trichomes
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