title: Higher Ammonium Transamination Capacity Can Alleviate Glutamate Inhibition on Winter Wheat (Triticum aestivum L.) Root Growth under High Ammonium Stress.
abstract: Most of the studies about NH4+ stress mechanism simply address the effects of free NH4+, failing to recognize the changed nitrogen assimilation products. The objective of this study was to elucidate the effects of glutamate on root growth under high ammonium (NH4+) conditions in winter wheat (Triticum aestivum L.). Hydroponic experiments were conducted using two wheat cultivars, AK58 (NH4+-sensitive) and Xumai25 (NH4+-tolerant) with either 5 mM NH4+ nitrogen (AN) as stress treatment or 5 mM nitrate (NO3-) nitrogen as control. To evaluate the effects of NH4+-assimilation products on plant growth, 1 μM L-methionine sulfoximine (MSO) (an inhibitor of glutamine synthetase (GS)) and 1 mM glutamates (a primary N assimilation product) were added to the solutions, respectively. The AN significantly reduced plant biomass, total root length, surface area and root volume in both cultivars, but less effect was observed in Xumai25. The inhibition effects were alleviated by the application of MSO but strengthened by the application of glutamate. The AN increased the activities of GS, glutamate dehydrogenase (GDH) in both cultivars, resulting in higher glutamate contents. However, its contents were decreased by the application of MSO. Compared to AK58, Xumai25 showed lower glutamate contents due to its higher activities of glutamic-oxaloacetic transaminase (GOT) and glutamic-pyruvic transaminase (GPT). With the indole-3-acetic acid (IAA) contents decreasing in roots, the ratio of shoot to root in IAA was increased, and further increased by the application of glutamate, and reduced by the application of MSO, but the ratio was lower in Xumai25. Meanwhile, the total soluble sugar contents and its root to shoot ratio also showed similar trends. These results indicate that the NH4+-tolerant cultivar has a greater transamination ability to prevent glutamate over-accumulation to maintain higher IAA transport ability, and consequently promoted soluble sugar transport to roots, further maintaining root growth.
authors: Key Laboratory of Crop Physiology, Ecology and Production Management, Nanjing Agricultural University, Nanjing, Jiangsu Province, 210095, P. R. China.
authors: Feng
authors: F
authors: Wang
authors: Key Laboratory of Crop Physiology, Ecology and Production Management, Nanjing Agricultural University, Nanjing, Jiangsu Province, 210095, P. R. China.
authors: Jingwen
authors: J
authors: Gao
authors: Key Laboratory of Crop Physiology, Ecology and Production Management, Nanjing Agricultural University, Nanjing, Jiangsu Province, 210095, P. R. China.
authors: Yang
authors: Y
authors: Liu
authors: Key Laboratory of Crop Physiology, Ecology and Production Management, Nanjing Agricultural University, Nanjing, Jiangsu Province, 210095, P. R. China.
authors: Zhongwei
authors: Z
authors: Tian
authors: Key Laboratory of Crop Physiology, Ecology and Production Management, Nanjing Agricultural University, Nanjing, Jiangsu Province, 210095, P. R. China.
authors: Abid
authors: A
authors: Muhammad
authors: Key Laboratory of Crop Physiology, Ecology and Production Management, Nanjing Agricultural University, Nanjing, Jiangsu Province, 210095, P. R. China.
authors: Yixuan
authors: Y
authors: Zhang
authors: Key Laboratory of Crop Physiology, Ecology and Production Management, Nanjing Agricultural University, Nanjing, Jiangsu Province, 210095, P. R. China.
authors: Dong
authors: D
authors: Jiang
authors: Key Laboratory of Crop Physiology, Ecology and Production Management, Nanjing Agricultural University, Nanjing, Jiangsu Province, 210095, P. R. China.
authors: Weixing
authors: W
authors: Cao
authors: Key Laboratory of Crop Physiology, Ecology and Production Management, Nanjing Agricultural University, Nanjing, Jiangsu Province, 210095, P. R. China.
authors: Tingbo
authors: T
authors: Dai
mesh_terms: D000410:Alanine Transaminase / Q000378:metabolism; D000586:Amination; D064751:Ammonium Compounds / Q000494:pharmacology*; D001219:Aspartate Aminotransferases / Q000378:metabolism; D005969:Glutamate Dehydrogenase / Q000037:antagonists & inhibitors*; D005974:Glutamate-Ammonia Ligase / Q000037:antagonists & inhibitors*; D018698:Glutamic Acid / Q000494:pharmacology*; D007210:Indoleacetic Acids / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development*; D018520:Plant Shoots / Q000187:drug effects / Q000254:growth & development; D014908:Triticum / Q000187:drug effects / Q000254:growth & development*
chemical_list: D064751:Ammonium Compounds; D007210:Indoleacetic Acids; D018698:Glutamic Acid; C030737:indoleacetic acid; D005969:Glutamate Dehydrogenase; D001219:Aspartate Aminotransferases; D000410:Alanine Transaminase; D005974:Glutamate-Ammonia Ligase