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  • 1
    Electronic Resource
    Electronic Resource
    Variation in competitive abilities of plants and microbes for specific amino acids (1999)
    Springer
    Biology and fertility of soils 29 (1999), S. 257-261 
    Details
    ISSN: 1432-0789
    Keywords: Key words Alpine nitrogen cycle ; Amino acids ; Kobresia myosuroides ; Organic nitrogen ; Plant-microbe competition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Microbes are assumed to possess strong competitive advantages over plants for uptake of nutrients from the soil. The finding that non-mycorrhizal plants can obtain a significant fraction of their N requirement from soil amino acids contradicts this assumption. The amino acid glycine (Gly) has been used as a model amino acid in many recent studies. Our preliminary studies showed that Gly was a poor substrate for microbial growth compared to other amino acids. We tested the hypothesis that the alpine sedge Kobresia myosuroides competes better for Gly than for other amino acids because of decreased microbial demand for this compound. Soil microbial populations that could grow using Gly as a sole carbon source were about 5 times lower than those that could grow on glutamate (Glu). Gly supported a significantly lower population than any of the ten other amino acids tested except serine. In contrast, K. myosuroides took up Gly from hydroponic solution at faster rates than Glu. In plant-soil microcosms, plants competed with soil microbes 3.25 times better for Gly than for Glu. We conclude that the low microbial demand and the rapid plant uptake of Gly relative to other amino acids allow Gly to be an especially important nitrogen source for K. myosuroides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050550
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  • 2
    Electronic Resource
    Electronic Resource
    Non-mycorrhizal uptake of amino acids by roots of the alpine sedge Kobresia myosuroides: implications for the alpine nitrogen cycle (1996)
    Springer
    Oecologia 108 (1996), S. 488-494 
    Details
    ISSN: 1432-1939
    Keywords: Alpine plants ; Nitrogen cycle ; Cyperaceae ; Tundra ; Organic nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Non-mycorrhizal plants of the alpine sedge, Kobresia myosuroides, take up the amino acid glycine from nutrient solutions at greater rates than NO inf3 sup- or NH inf4 sup+ . The amino acids glutamate and proline were also taken up at high rates. Total plant biomass was twice as high after 4 months of growth on glycine, compared to NH4NO3, with significant increases in both root and leaf biomass. By taking advantage of differences in the δ13C signature of air in the growth chamber and the glycine used for growth, a two-member mixing model was used to estimate that a significant amount of the glycine was taken up as intact molecules, enough to contribute 16% of the total carbon assimilation over a 4-month growing period. Glycine uptake was inhibited when roots were exposed to N2 in place of air, and when the protonophore carbonyl cyanide m-chlorophenylhydrazone (CCCP) was added to the root solution. From these results it is concluded that glycine uptake occurs through active transport. Glycine uptake exhibited a Q10 of 2.0 over the temperature range 5–15° C, with relatively high rates maintained at the lowest temperature measured (5° C). Roots of Kobreasia were not capable of taking up NH inf4 sup+ at measureable rates. To our knowledge, this is the first report of a plant whose non-mycorrhizal roots cannot take up NH inf4 sup+ . Measurements of three N fractions (NO inf3 sup- , NH inf4 sup+ , and total amino acids) in the soil pore water were made over two growing seasons in two Kobresia dry meadows using microlysimeters. At the West Knoll site, which is characterized by soils with average amounts of organic matter, the dominant forms of N in the soil pore water were NO inf3 sup- and NH inf4 sup+ (0–450 μmol L-1). Amino acid concentrations were generally less than 20 μmol L-1 at this site. At the East Knoll site, which is characterized by soils with higher than average amounts of organic matter, amino acids were generally present at higher concentrations (17–100 μmol L-1), compared to NO inf3 sup- and NH inf4 sup+ . The most abundant amino acids were glycine (10–100 μmol L-1), glutamate (5–70 μmol L-1), and late in the season cystein (5–15 μmol L-1). The results demonstrate that this sedge, which dominates dry meadow communities in many alpine ecosystems, is capable of taking up intact amino acids as a principal N source, and has access to high amino acid concentrations in certain alpine soils. Such uptake of organic N may accommodate plant N demands in the face of slow alpine N mineralization rates due to cold soil temperatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00333725
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  • 3
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    Positive regulation of T cell activation and integrin adhesion by the adapter Fyb/Slap (2001)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2001-09-22
    Description: The molecular adapter Fyb/Slap regulates signaling downstream of the T cell receptor (TCR), but whether it plays a positive or negative role is controversial. We demonstrate that Fyb/Slap-deficient T cells exhibit defective proliferation and cytokine production in response to TCR stimulation. Fyb/Slap is also required in vivo for T cell-dependent immune responses. Functionally, Fyb/Slap has no apparent role in the activation of known TCR signaling pathways, F-actin polymerization, or TCR clustering. Rather, Fyb/Slap regulates TCR-induced integrin clustering and adhesion. Thus, Fyb/Slap is the first molecular adapter to be identified that couples TCR stimulation to the avidity modulation of integrins governing T cell adhesion.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Griffiths, E K -- Krawczyk, C -- Kong, Y Y -- Raab, M -- Hyduk, S J -- Bouchard, D -- Chan, V S -- Kozieradzki, I -- Oliveira-Dos-Santos, A J -- Wakeham, A -- Ohashi, P S -- Cybulsky, M I -- Rudd, C E -- Penninger, J M -- New York, N.Y. -- Science. 2001 Sep 21;293(5538):2260-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Amgen Institute, 620 University Avenue, Toronto, Ontario, Canada M5G 2C1.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11567140" target="_blank"〉PubMed〈/a〉
    Keywords: Actins/metabolism ; *Adaptor Proteins, Signal Transducing ; Animals ; Antigens, CD/metabolism ; Antigens, CD3/metabolism ; Antigens, Differentiation, T-Lymphocyte/metabolism ; B-Lymphocytes/immunology ; Carrier Proteins/genetics/*physiology ; Cell Adhesion ; Cell Adhesion Molecules/metabolism ; Chimera ; Gene Targeting ; Humans ; Immunization ; Immunoglobulin G/biosynthesis ; Integrins/*metabolism ; Intercellular Adhesion Molecule-1/metabolism ; Interferon-gamma/biosynthesis ; Interleukin-2/biosynthesis/pharmacology ; Lectins, C-Type ; *Lymphocyte Activation ; Lymphocyte Function-Associated Antigen-1/metabolism ; Mice ; Phosphoproteins/genetics/*physiology ; Receptors, Antigen, T-Cell/immunology/metabolism ; Receptors, Interleukin-2/metabolism ; Recombinant Proteins/metabolism ; Signal Transduction ; T-Lymphocytes/immunology/metabolism/*physiology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 4
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    Mimicry of CD40 signals by Epstein-Barr virus LMP1 in B lymphocyte responses (1999)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1999-10-09
    Description: The effect of the Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1) on the activation and differentiation of normal B cells was investigated. B cells of transgenic mice expressing LMP1 under the control of immunoglobulin promoter/enhancer displayed enhanced expression of activation antigens and spontaneously proliferated and produced antibody. Humoral immune responses of LMP1 transgenic mice in CD40-deficient or normal backgrounds revealed that LMP1 mimics CD40 signals to induce extrafollicular B cell differentiation but, unlike CD40, blocks germinal center formation. Thus, these specific properties of LMP1 may determine the site of primary B cell infection and the state of infection in the natural course of EBV infection, whereas subsequent loss of LMP1 expression may affect the site of persistent latent infection.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Uchida, J -- Yasui, T -- Takaoka-Shichijo, Y -- Muraoka, M -- Kulwichit, W -- Raab-Traub, N -- Kikutani, H -- CA19014/CA/NCI NIH HHS/ -- New York, N.Y. -- Science. 1999 Oct 8;286(5438):300-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Molecular Immunology, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamada-oka, Suita, Osaka 565-0871, Japan.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/10514374" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Antibody Affinity ; Antigens, CD40/genetics/*metabolism ; B-Lymphocytes/*immunology/metabolism/virology ; Cell Differentiation ; Female ; Germinal Center/immunology/metabolism ; Herpesvirus 4, Human/*metabolism/physiology ; Immunization ; Immunoglobulin Class Switching ; Immunoglobulins/biosynthesis ; Interleukin-4/pharmacology ; *Lymphocyte Activation ; Male ; Mice ; Mice, Inbred C57BL ; Mice, Transgenic ; *Molecular Mimicry ; NF-kappa B/metabolism ; Signal Transduction ; Spleen/immunology ; Viral Matrix Proteins/genetics/*metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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