Asparagine is an important nitrogen storage and transport molecule, but its accumulation as a free amino acid in crops has implications for food safety because free asparagine is a precursor for acrylamide formation during cooking and processing. Asparagine synthesis occurs by the amidation of aspartate, catalysed by asparagine synthetase, and this study concerned the expression of asparagine synthetase (TaASN) genes in wheat. The expression of three genes, TaASN1-3, was studied in different tissues and in response to nitrogen and sulphur supply. The expression of TaASN2 in the embryo and endosperm during mid to late grain development was the highest of any of the genes in any tissue. Both TaASN1 and TaASN2 increased in expression through grain development, and in the grain of field-grown plants during mid-development in response to sulphur deprivation. However, only TaASN1 was affected by nitrogen or sulphur supply in pot-based experiments, showing complex tissue-specific and developmentally-changing responses. A putative N-motif or GCN4-like regulatory motif was found in the promoter of TaASN1 genes from several cereal species. As the study was completed, a fourth gene, TaASN4, was identified from recently available genome data. Phylogenetic analysis showed that other cereal species have similar asparagine synthetase gene families to wheat.

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食品安全：小麦天冬酰胺合成酶基因家族的结构与表达

天冬酰胺是一种重要的氮储存和运输分子，但它作为游离氨基酸在作物中的积累对食品安全有影响，因为游离天冬酰胺是烹饪和加工过程中丙烯酰胺形成的前体。天冬酰胺合成由天冬氨酸的酰胺化发生，由天冬酰胺合成酶催化，本研究涉及天冬酰胺合成酶 (TaASN) 基因在小麦中的表达。研究了三个基因 TaASN1-3 在不同组织中的表达以及对氮和硫供应的反应。TaASN2 在籽粒发育中后期的胚胎和胚乳中的表达是任何组织中任何基因中最高的。TaASN1 和 TaASN2 在籽粒发育过程中表达增加，以及在发育中期的田间植物的谷物中，以应对硫缺乏。然而，在基于锅的实验中，只有 TaASN1 受到氮或硫供应的影响，显示出复杂的组织特异性和发育变化反应。在来自几种谷物物种的 TaASN1 基因的启动子中发现了一个推定的 N 基序或 GCN4 样调控基序。随着研究的完成，第四个基因 TaASN4 从最近可用的基因组数据中被识别出来。系统发育分析表明，其他谷类物种具有与小麦相似的天冬酰胺合成酶基因家族。在来自几种谷物物种的 TaASN1 基因的启动子中发现了一个推定的 N 基序或 GCN4 样调控基序。随着研究的完成，第四个基因 TaASN4 从最近可用的基因组数据中被识别出来。系统发育分析表明，其他谷类物种具有与小麦相似的天冬酰胺合成酶基因家族。在来自几种谷物物种的 TaASN1 基因的启动子中发现了一个推定的 N 基序或 GCN4 样调控基序。随着研究的完成，第四个基因 TaASN4 从最近可用的基因组数据中被识别出来。系统发育分析表明，其他谷类物种具有与小麦相似的天冬酰胺合成酶基因家族。