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  • essential amino acids  (2)
  • Arabidopsis  (1)
  • Earth Resources and Remote Sensing; Statistics and Probability  (1)
  • FMR1  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Cloning and expression of an Arabidopsis thaliana cDNA encoding a monofunctional aspartate kinase homologous to the lysine-sensitive enzyme of Escherichia coli (1997)
    Springer
    Plant molecular biology 34 (1997), S. 287-294 
    Details
    ISSN: 1573-5028
    Keywords: aspartate kinase ; cDNA ; essential amino acids ; lysine ; threonine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract As in many bacterial species, the first enzymatic reaction of the aspartate-family pathway in plants is mediated by several isozymes of aspartate kinase (AK) that are subject to feedback inhibition by the end-product amino acids lysine or threonine. So far, only cDNAs and genes encoding threonine-sensitive AKs have been cloned from plants. These were all shown to encode polypeptides containing two linked activities, namely AK and homoserine dehydrogenase (HSD), similar to the Escherichia coli thrA gene encoding a threonine-sensitive bifunctional AK/HSD isozyme. In the present report, we describe the cloning of a new Arabidopsis thaliana cDNA that is relatively highly homologous to the E. coli lysC gene encoding the lysine-sensitive AK isozyme. Moreover, similar to the bacterial lysine-sensitive AK, the polypeptide encoded by the present cDNA is monofunctional and does not contain an HSD domain. These observations imply that our cloned cDNA encodes a lysine-sensitive AK. Southern blot hybridization detected a single gene highly homologous to the present cDNA, plus an additional much less homologous gene. This was confirmed by the independent cloning of an additional Arabidopsis cDNA encoding a lysine-sensitive AK (see accompanying paper). Northern blot analysis suggested that the gene encoding this monofunctional AK cDNA is abundantly expressed in most if not all tissues of Arabidopsis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005849228945
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Lysine and threonine metabolism are subject to complex patterns of regulation in Arabidopsis (1996)
    Springer
    Plant molecular biology 32 (1996), S. 727-734 
    Details
    ISSN: 1573-5028
    Keywords: Arabidopsis ; essential amino acids ; lysine ; threonine ; transgenic plants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To study the regulation of lysine and threonine metabolism in plants, we have transformed Arabidopsis thaliana with chimeric genes encoding the two bacterial enzymes dihydrodipicolinate synthase (DHPS) and aspartate kinase (AK). These bacterial enzymes are much less sensitive to feedback inhibition by lysine and threonine than their plant counterparts. Transgenic plants expressing the bacterial DHPS overproduced lysine, but lysine levels were quite variable within and between transgenic genotypes and there was no direct correlation between the levels of free lysine and the activity of DHPS. The most lysine-overproducing plants also exhibited abnormal phenotypes. However, these phenotypes were detected only at early stages of plant growth, while at later stages, new buds emerged that looked completely normal and set seeds. Wild-type plants exhibited relatively high levels of free threonine, suggesting that in Arabidopsis AK regulation may be more relaxed than in other plants. This was also supported by the fact that expression of the bacterial AK did not cause any dramatic elevation in this amino acid. Yet, the relaxed regulation of threonine synthesis in Arabidopsis was not simply due to a reduced sensitivity of the endogenous AK to feedback inhibition by lysine and threonine because growth of wild-type plants, but not of transgenic plants expressing the bacterial AK, was arrested in media containing these two amino acids. The present results, combined with previous studies from our laboratory, suggest that the regulation of lysine and threonine metabolism is highly variable among plant species and is subject to complex biochemical, physiological and environmental controls. The suitability of these transgenic Arabidopsis plants for molecular and genetic dissection of lysine and threonine metabolism is also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00020213
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    Paper (German National Licenses)
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  • 3
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    Early Season Large-Area Winter Crop Mapping Using MODIS NDVI Data, Growing Degree Days Information and a Gaussian Mixture Model (2017)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Knowledge on geographical location and distribution of crops at global, national and regional scales is an extremely valuable source of information applications. Traditional approaches to crop mapping using remote sensing data rely heavily on reference or ground truth data in order to train/calibrate classification models. As a rule, such models are only applicable to a single vegetation season and should be recalibrated to be applicable for other seasons. This paper addresses the problem of early season large-area winter crop mapping using Moderate Resolution Imaging Spectroradiometer (MODIS) derived Normalized Difference Vegetation Index (NDVI) time-series and growing degree days (GDD) information derived from the Modern-Era Retrospective analysis for Research and Applications (MERRA-2) product. The model is based on the assumption that winter crops have developed biomass during early spring while other crops (spring and summer) have no biomass. As winter crop development is temporally and spatially non-uniform due to the presence of different agro-climatic zones, we use GDD to account for such discrepancies. A Gaussian mixture model (GMM) is applied to discriminate winter crops from other crops (spring and summer). The proposed method has the following advantages: low input data requirements, robustness, applicability to global scale application and can provide winter crop maps 1.5-2 months before harvest. The model is applied to two study regions, the State of Kansas in the US and Ukraine, and for multiple seasons (2001-2014). Validation using the US Department of Agriculture (USDA) Crop Data Layer (CDL) for Kansas and ground measurements for Ukraine shows that accuracies of greater than 90% can be achieved in mapping winter crops 1.5-2 months before harvest. Results also show good correspondence to official statistics with average coefficients of determination R(exp. 2) greater than 0.85.
    Keywords: Earth Resources and Remote Sensing; Statistics and Probability
    Type: GSFC-E-DAA-TN46331 , Remote Sensing of Environment (ISSN 0034-4257) (e-ISSN 1879-0704); 195; 244-258
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Towards Mechanism-based Treatments for Fragile X Syndrome (2021)
    MDPI - Multidisciplinary Digital Publishing Institute
    Details
    Publication Date: 2024-04-05
    Description: It has been more than 25 years since the identification of the FMR1 gene and the demonstration of the causative role of CGG-repeat expansion in the disease pathology of fragile X syndrome (FXS), but the underlying mechanisms involved in the expansion mutation and the resulting gene silencing still remain elusive. Our understanding of the pathways impacted by the loss of FMRP function has grown tremendously, and has opened new avenues for targeted treatments for FXS. However, the failure of recent clinical trials that were based on successful preclinical studies using the Fmr1 knockout mouse model has forced the scientific community to revisit clinical trial design and identify objective outcome measures. There has also been a renewed interest in restoring FMR1 gene expression as a possible treatment approach for FXS. This special issue of Brain Sciences highlights the progress that has been made towards understanding the disease mechanisms and how this has informed the development of treatment strategies that are being explored for FXS.
    Keywords: QH301-705.5 ; Q1-390 ; n/a ; lymphoblast ; pluripotent stem cells ; FMR1 ; Gene editing ; X chromosome ; Fmr1 ; epigenetic gene silencing ; FMR1 gene ; Fragile X syndrome 1 ; repeat instability ; characteristics that have the greatest impact ; DNA instability ; working memory ; language development ; mosaicism ; CRISPR 3 ; clinical trials ; autism spectrum disorders ; Fmr1 KO mouse ; automated vocal analysis ; base excision repair (BER) ; inhibitory control ; cerebral spinal fluid ; iPSC ; drug development ; targeted treatments ; molecular biomarkers ; viral vector ; avoidance ; biomarker ; set-shifting ; early identification ; expansion ; anxiety ; planning ; voice of the person ; mismatch repair (MMR) ; gene reactivation ; double-strand break repair (DSBR) ; newborn screening ; intellectual disability ; processing speed ; voice of the patient ; fragile X syndrome ; adeno-associated virus ; neurodevelopmental disorders ; histone methylation ; Non-homologous end-joining (NHEJ) ; ASD ; Fxr2 ; Fragile X-associated Tremor/Ataxia Syndrome 2 ; Trinucleotide Repeat 4 ; CGG Repeat Expansion Disease ; DNA methylation ; contraction ; fragile X mental retardation protein ; RNA:DNA hybrid ; behavior ; developmental disorders ; cognition ; females ; FMRP ; Fragile X Syndrome ; unstable repeat diseases ; protein synthesis ; brain ; cognitive flexibility ; treatment development ; fibroblast ; PRC2 ; transcription coupled repair (TCR) ; best practices ; attention ; Fragile X ; executive function ; thema EDItEUR::P Mathematics and Science::PS Biology, life sciences
    Language: English
    Format: application/octet-stream
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    E-BOOK
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