Postles Jennifer, Curtis Tanya Y, Powers Stephen J, Elmore J S, Mottram Donald S, Halford Nigel G
Plant Biology and Crop Science Department, Rothamsted ResearchHarpenden, UK; Biotechnology and Biological Sciences Research CouncilSwindon, UK.
Plant Biology and Crop Science Department, Rothamsted Research Harpenden, UK.
Front Plant Sci. 2016 Jun 22;7:917. doi: 10.3389/fpls.2016.00917. eCollection 2016.
Free asparagine plays a central role in nitrogen storage and transport in many plant species due to its relatively high ratio of nitrogen to carbon. However, it is also a precursor for acrylamide, a Class 2a carcinogen that forms during high-temperature processing and cooking. The concentration of free asparagine was shown to increase by approximately 70% in rye grain in response to severe sulfur deficiency (F-test, p = 0.004), while the concentration of both free asparagine and free glutamine increased (by almost threefold and approximately 62%, respectively) in response to nitrogen application (F-test, p < 0.001 for free asparagine; p = 0.004 for free glutamine). There were also effects of nutrient supply on other free amino acids: The concentration of free proline, for example, showed a significant (F-test, p = 0.019) effect of nitrogen interacting with sulfur, with the highest concentration occurring when the plants were deprived of both nitrogen and sulfur. Polymerase chain reaction products for several genes involved in asparagine metabolism and its regulation were amplified from rye grain cDNA. These genes were asparagine synthetase-1 (ScASN1), glutamine synthetase-1 (ScGS1), potassium-dependent asparaginase (ScASP), aspartate kinase (ScASK), and general control non-derepressible-2 (ScGCN2). The expression of these genes and of a previously described sucrose non-fermenting-1-related protein kinase-1 gene (ScSnRK1) was analyzed in flag leaf and developing grain in response to nitrogen and sulfur supply, revealing a significant (F-test, p < 0.05) effect of nitrogen supply on ScGS1 expression in the grain at 21 days post-anthesis. There was also evidence of an effect of sulfur deficiency on ScASN1 gene expression. However, although this effect was large (almost 10-fold) it was only marginally statistically significant (F-test, 0.05 < p < 0.10). The study reinforced the conclusion that nutrient availability can have a profound impact on the concentrations of different free amino acids, something that is often overlooked by plant physiologists but which has important implications for flavor, color, and aroma development during cooking and processing, as well as the production of undesirable contaminants such as acrylamide.
由于游离天冬酰胺的氮碳比相对较高，它在许多植物物种的氮储存和运输中起着核心作用。然而，它也是丙烯酰胺的前体，丙烯酰胺是一种2a类致癌物，在高温加工和烹饪过程中形成。研究表明，严重缺硫时黑麦籽粒中游离天冬酰胺的浓度增加约70%（F检验，p = 0.004），而施氮时游离天冬酰胺和游离谷氨酰胺的浓度均增加（分别增加近三倍和约62%）（游离天冬酰胺的F检验，p < 0.001；游离谷氨酰胺的p = 0.004）。养分供应对其他游离氨基酸也有影响：例如，游离脯氨酸的浓度显示出氮与硫相互作用的显著影响（F检验，p = 0.019），当植物同时缺乏氮和硫时，其浓度最高。从黑麦籽粒cDNA中扩增出了几个参与天冬酰胺代谢及其调控的基因的聚合酶链反应产物。这些基因是天冬酰胺合成酶-1（ScASN1）、谷氨酰胺合成酶-1（ScGS1）、钾依赖性天冬酰胺酶（ScASP）、天冬氨酸激酶（ScASK）和一般控制非抑制性-2（ScGCN2）。分析了这些基因以及先前描述的蔗糖非发酵-1相关蛋白激酶-1基因（ScSnRK1）在旗叶和发育籽粒中对氮和硫供应的响应表达，结果显示，花后21天氮供应对籽粒中ScGS1表达有显著影响（F检验，p < 0.05）。也有证据表明缺硫对ScASN1基因表达有影响。然而，尽管这种影响很大（近10倍），但在统计学上只是勉强显著（F检验，0.05 < p < 0.10）。该研究强化了这样一个结论，即养分有效性会对不同游离氨基酸的浓度产生深远影响，这一点常常被植物生理学家忽视，但对烹饪和加工过程中的风味、颜色和香气形成，以及丙烯酰胺等不良污染物的产生具有重要意义。
