Quantification and enzyme targets of fatty acid amides from duckweed root exudates involved in the stimulation of denitrification
Quantification and enzyme targets of fatty acid amides from duckweed root exudates involved in the stimulation of denitrification
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DOI：
10.1016/j.jplph.2016.04.010
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发表时间：
2016-07-01
影响因子：
4.3
通讯作者：
Shi, Weiming
中科院分区：
文献类型：
--
作者：
Sun, Li;Lu, Yufang;Shi, Weiming
植物根系分泌物中的脂肪酸酰胺，如油酰胺和芥子酰胺，能够参与植物与微生物的强烈相互作用，刺激根际细菌的氮代谢。然而，这些脂肪酸酰胺的分泌机制及其对微生物代谢的刺激活性的性质尚未得到研究。比较了浮萍根分泌物中油酰胺和芥子酰胺的采集、预处理和测定方法。气相色谱法（GC）的检出限分别为10.3 μ gmL（-1）和16.1 μ gmL(-1)，远低于液相色谱法（LC）的检出限（分别为1.7 μ gmL和5.0 μ gmL(-1)）。定量GC分析结果表明，连续采集法在多根螺旋藻根分泌物中所含的油酰胺和芥子酰胺含量分别为50.20 +/- 4.32和76.79 +/- 13.92 μ g kg(-1) FW day(-1)，是静态采集法(10.88 +/- 0.66和15.27 +/- 0.58 μ g kg(-1) FW day（-1）的5倍。此外，高氮（>300 mg L-1）显著增加了浮萍的脂肪酸酰胺分泌，且与浮萍的相对生长率呈负相关。机制分析表明，芥子酰胺通过增强细菌的反硝化作用来促进氮的去除，其作用目标是两种关键的反硝化酶，硝酸盐还原酶和亚硝酸盐还原酶。我们的研究结果有助于我们理解自然生态系统中植物根系分泌物对氮动态的调节。(C) 2016 Elsevier GmbH版权所有。
Fatty acid amides from plant root exudates, such as oleamide and erucamide, have the ability to participate in strong plant-microbe interactions, stimulating nitrogen metabolism in rhizospheric bacteria. However, mechanisms of secretion of such fatty acid amides, and the nature of their stimulatory activities on microbial metabolism, have not been examined. In the present study, collection, pre-treatment, and determination methods of oleamide and erucamide in duckweed root exudates are compared. The detection limits of oleamide and erucamide by gas chromatography (GC) (10.3 ng mL(-1) and 16.1 ngmL(-1), respectively) are shown to be much lower than those by liquid chromatography (LC) (1.7 and 5.0 mu g mL(-1), respectively). Quantitative GC analysis yielded five times larger amounts of oleamide and erucamide in root exudates of Spirodela polyrrhiza when using a continuous collection method (50.20 +/- 4.32 and 76.79 +/- 13.92 mu g kg(-1) FW day(-1)), compared to static collection (10.88 +/- 0.66 and 15.27 +/- 0.58 mu g kg(-1) FW day(-1)). Furthermore, fatty acid amide secretion was significantly enhanced under elevated nitrogen conditions (>300 mg L-1), and was negatively correlated with the relative growth rate of duckweed. Mechanistic assays were conducted to show that erucamide stimulates nitrogen removal by enhancing denitrification, targeting two key denitrifying enzymes, nitrate and nitrite reductases, in bacteria. Our findings significantly contribute to our understanding of the regulation of nitrogen dynamics by plant root exudates in natural ecosystems. (C) 2016 Elsevier GmbH. All rights reserved.