caa a22 4500 606207821 CHVBK 20210128101019.0 cr unu---uuuuu 210128e20151201xx s 000 0 eng 10.1007/s00425-015-2371-8 doi (NATIONALLICENCE)springer-10.1007/s00425-015-2371-8 Glutamine synthetase activity in leaves of Zea mays L. as influenced by magnesium status [Elektronische Daten] [Mareike Jezek, Christoph-Martin Geilfus, Karl-Hermann Mühling] Main conclusion : The total capacity of the GS-mediated ligation of free ammonium and glutamate to form glutamine in the leaves of maize plants is not impaired upon severe magnesium starvation. Magnesium deficiency does not obligatorily lead to the decreased total protein concentrations in the leaves. Abstract: Magnesium (Mg) is an integral component of the enzyme glutamine synthetase (GS), having both a structural and a catalytic role. Moreover, Mg is relevant for the post-translational regulation of the GS. Glutamine synthetase is one of the key enzymes in nitrogen assimilation, ligating-free ammonium (NH4 +) to glutamate to form glutamine and it is therefore crucial for plant growth and productivity. This study was conducted in order to test whether a severe Mg-deficiency impairs the total capacity of the GS-catalyzed synthesis of glutamine in maize leaves. Maize was grown hydroponically and the GS activity was analyzed dependent on different leaf developmental stages. Glutamine synthetase activity in vitro assays in combination with immune-dot blot analysis revealed that both the total activity and the abundance of glutamine synthetase was not impaired in the leaves of maize plants upon 54days of severe Mg starvation. Additionally, it was shown that Mg deficiency does not obligatorily lead to decreased total protein concentrations in the leaves, as assayed by Bradford protein quantification. Moreover, Mg resupply to the roots or the leaves of Mg-deficient plants reversed the Mg-deficiency-induced accumulation of free amino acids in older leaves, which indicates impaired phloem loading. The results of our study reveal that the total GS-mediated primary or secondary assimilation of free NH4 + is not a limiting enzymatic reaction under Mg deficiency and thus cannot be accountable for the observed restriction of plant growth and productivity in Mg-deficient maize. Springer-Verlag Berlin Heidelberg, 2015 Magnesium deficiency nationallicence Maize nationallicence Glutamine synthetase nationallicence Protein concentration nationallicence Amino acid pattern nationallicence Nitrogen assimilation nationallicence Foliar fertilization nationallicence Asn : Asparagine nationallicence FW : Fresh weight nationallicence GHA : γ-glutamyl hydroxamate nationallicence Gln : Glutamine nationallicence Glu : Glutamate nationallicence GS : Glutamine synthetase nationallicence NS : Nutrient solution nationallicence Jezek Mareike Institute of Plant Nutrition and Soil Science, Kiel University, Hermann-Rodewald-Straße 2, 24118, Kiel, Germany aut Geilfus Christoph-Martin Institute of Plant Nutrition and Soil Science, Kiel University, Hermann-Rodewald-Straße 2, 24118, Kiel, Germany aut Mühling Karl-Hermann Institute of Plant Nutrition and Soil Science, Kiel University, Hermann-Rodewald-Straße 2, 24118, Kiel, Germany aut Planta Springer Berlin Heidelberg 242/6(2015-12-01), 1309-1319 0032-0935 242:6<1309 2015 242 425 https://doi.org/10.1007/s00425-015-2371-8 text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s00425-015-2371-8 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Jezek Mareike Institute of Plant Nutrition and Soil Science, Kiel University, Hermann-Rodewald-Straße 2, 24118, Kiel, Germany aut NATIONALLICENCE 700 1- Geilfus Christoph-Martin Institute of Plant Nutrition and Soil Science, Kiel University, Hermann-Rodewald-Straße 2, 24118, Kiel, Germany aut NATIONALLICENCE 700 1- Mühling Karl-Hermann Institute of Plant Nutrition and Soil Science, Kiel University, Hermann-Rodewald-Straße 2, 24118, Kiel, Germany aut NATIONALLICENCE 773 0- Planta Springer Berlin Heidelberg 242/6(2015-12-01), 1309-1319 0032-0935 242:6<1309 2015 242 425