title: Metabolic indicators of drought stress tolerance in wheat: glutamine synthetase isoenzymes and Rubisco.
abstract: Drought stress has a considerable impact on the ecosystem and agriculture. Continuous water deficit induces early leaf senescence in plants. During this process, chloroplasts are degraded and photosynthesis drastically drops. The objective of this investigation was to look into the regulation of nitrogen and carbon metabolism during water deficit. Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase; EC 4.1.1.39) and the total protein contents inform us of the sink-source relation in plants. Glutamine synthetase (GS, EC 6.3.1.2) isoenzymes are good markers of plastid status (GS2) and the nitrogen metabolism (GS1). Tolerant and sensitive wheat (Triticum aestivum L.) genotypes were tested, which are widely used in agriculture. The amount of protein, Rubisco and GS isoforms in leaves were measured during the grain filling period, as indicative traits that ultimately determine the onset and stage of senescence. The symptoms of senescence first appeared on the oldest and finally on the youngest leaves. Drought stress disrupted the sequentiality of senescence in the sensitive varieties. An untimely senescence appeared in flag leaves, earlier than in the older leaves. Total protein and Rubisco contents decreased and the GS2 isoenzyme declined considerably in the youngest leaves. In the tolerant varieties, however, these physiological parameters did not change under drought, only the sequential senescence of leaf levels accelerated in some cases compared to the control, well-watered plants. Our results revealed that GS is a good indicator of drought stress, which can be applied for the characterization of wheat cultivars in terms of drought stress tolerance.
authors.affiliation: Department of Plant Biology, University of Szeged, H-6701 Szeged, Közép Fasor 52, Hungary.
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Nagy
authors.affiliation: Department of Plant Biology, University of Szeged, H-6701 Szeged, Közép Fasor 52, Hungary.
authors.forename: Edit
authors.initials: E
authors.lastname: Németh
authors.affiliation: Department of Plant Biology, University of Szeged, H-6701 Szeged, Közép Fasor 52, Hungary.
authors.forename: Adrienn
authors.initials: A
authors.lastname: Guóth
authors.affiliation: Cereal Research Non-Profit Company, P.O. Box 391, H-6701 Szeged, Hungary.
authors.forename: Lajos
authors.initials: L
authors.lastname: Bona
authors.affiliation: Department of Plant Biology, University of Szeged, H-6701 Szeged, Közép Fasor 52, Hungary.
authors.forename: Barnabás
authors.initials: B
authors.lastname: Wodala
authors.affiliation: Department of Plant Biology, University of Szeged, H-6701 Szeged, Közép Fasor 52, Hungary. Electronic address: pecsvaradi@bio.u-szeged.hu.
authors.forename: Attila
authors.initials: A
authors.lastname: Pécsváradi
mesh_terms: D055864:Droughts; D018506:Gene Expression Regulation, Plant; D005974:Glutamate-Ammonia Ligase / Q000235:genetics / Q000378:metabolism*; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism / Q000502:physiology; D012273:Ribulose-Bisphosphate Carboxylase / Q000235:genetics / Q000378:metabolism*; D014908:Triticum / Q000378:metabolism* / Q000502:physiology
chemical_list: D007527:Isoenzymes; D012273:Ribulose-Bisphosphate Carboxylase; D005974:Glutamate-Ammonia Ligase
keywords: Drought stress; Glutamine synthetase; Rubisco; Senescence; Wheat