Higher Ammonium Transamination Capacity Can Alleviate Glutamate Inhibition on Winter Wheat (Triticum aestivum L.) Root Growth under High Ammonium Stress.
Higher Ammonium Transamination Capacity Can Alleviate Glutamate Inhibition on Winter Wheat (Triticum aestivum L.) Root Growth under High Ammonium Stress.
复制标题
较高的铵转氨能力可以减轻高铵胁迫下谷氨酸对冬小麦 (Triticum aestivum L.) 根系生长的抑制
DOI：
10.1371/journal.pone.0160997
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发表时间：
2016
期刊：
影响因子：
3.7
通讯作者：
Dai T
中科院分区：
文献类型：
--
作者：
Wang F;Gao J;Liu Y;Tian Z;Muhammad A;Zhang Y;Jiang D;Cao W;Dai T
目前关于NH 4+胁迫机理的研究大多只关注游离NH 4+的影响，而没有认识到NH 4+胁迫对氮同化产物的影响。研究了谷氨酸对高铵条件下冬小麦根系生长的影响。以2个小麦品种AK 58（NH 4+敏感）和徐麦25（NH 4+耐受）为材料，进行水培试验，以5 mM NH 4+氮（AN）为胁迫处理，以5 mM NO3-氮（NO 3-）为对照。为了评价NH 4+同化产物对植物生长的影响，将1 μM L-甲硫氨酸亚砜亚胺（MSO）（谷氨酰胺合成酶（GS）的抑制剂）和1 mM谷氨酸盐（初级N同化产物）分别添加到溶液中。硝酸铵处理显著降低了两个品种的生物量、总根长、表面积和根体积，但对徐麦25的影响较小。MSO的抑制作用减弱，而谷氨酸的抑制作用增强。硝酸铵处理提高了两个品种的谷氨酰胺合成酶（GS）和谷氨酸脱氢酶（GDH）的活性，使谷氨酸含量增加。但施用MSO后，其含量降低。与AK 58相比，徐麦25的谷草转氨酶（GOT）和谷丙转氨酶（GPT）活性较高，谷氨酸含量较低。随着根系中吲哚乙酸（IAA）含量的降低，IAA的地上部/根比增加，施用谷氨酸后IAA的地上部/根比进一步增加，施用MSO后IAA的地上部/根比降低，但徐麦25的地上部/根比较低。同时，可溶性总糖含量和根冠比也表现出类似的变化趋势。这些结果表明，耐NH 4+的品种具有更强的转氨能力，以防止谷氨酸过度积累，以维持较高的IAA运输能力，从而促进可溶性糖运输到根部，进一步维持根系生长。
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.