Chevalier C, Bourgeois E, Just D, Raymond P
Station de Physiologie Végétale, Institut National de la Recherche Agronomique, Villenave d'Ornon, France.
Plant J. 1996 Jan;9(1):1-11. doi: 10.1046/j.1365-313x.1996.09010001.x.
Differential hybridization of a cDNA library constructed with poly(A)+ mRNA from 24 h starved maize (Zea mays L.) root tips, resulted in the isolation of a cDNA (called pZSS1) that was highly induced during glucose deprivation. The nucleotide sequence analysis of the full-length cDNA allowed its identification by comparison with sequence data bases. The 586 amino acid sequence encoded by pZSS1 was shown to be about 60% identical to sequences of asparagine synthetases (EC 6.3.5.4) from Asparagus officinalis, Pisum sativum, Arabidopsis thaliana and Brassica oleracea. Southern blot analysis of maize genomic DNA showed that asparagine synthetase may be encoded by at least two genes. The use of a specific probe for the 3' untranslated region of pZSS1 in Northern blot experiments, revealed that the isolated AS gene was essentially expressed in roots of maize seedlings. Time course analysis revealed that maximal expression of the gene corresponding to pZSS1 occurs between 18 and 24 h after the onset of the starvation treatment. The steady-state levels of transcripts in maize root tips were found to change under various incubation conditions. Exogenous supply of metabolizable sugars downregulated the gene expression, while carbohydrate deprivation or feeding with non-metabolizable sugars resulted in the induction of gene expression. In addition to carbohydrate deprivation, the effects of nitrogen metabolite supply and stress conditions indicate that gene expression might be under metabolic control in maize root tips. The intracellular nitrogen to carbon ratio might be an important factor for the regulation of asparagine synthetase gene expression.
用来自饥饿24小时的玉米（Zea mays L.）根尖的聚腺苷酸加尾mRNA构建cDNA文库，通过差异杂交分离出一个在葡萄糖缺乏时被高度诱导的cDNA（称为pZSS1）。对全长cDNA的核苷酸序列分析使其能够通过与序列数据库比较来鉴定。pZSS1编码的586个氨基酸序列与芦笋、豌豆、拟南芥和甘蓝的天冬酰胺合成酶（EC 6.3.5.4）序列约60%相同。玉米基因组DNA的Southern印迹分析表明，天冬酰胺合成酶可能由至少两个基因编码。在Northern印迹实验中使用针对pZSS1 3'非翻译区的特异性探针，揭示分离的AS基因主要在玉米幼苗根中表达。时间进程分析表明，对应于pZSS1的基因在饥饿处理开始后第18至24小时达到最大表达。发现玉米根尖转录本的稳态水平在不同培养条件下会发生变化。可代谢糖的外源供应下调基因表达，而碳水化合物缺乏或用不可代谢糖喂养则导致基因表达的诱导。除了碳水化合物缺乏外，氮代谢物供应和胁迫条件的影响表明，玉米根尖中的基因表达可能受代谢控制。细胞内氮碳比可能是调节天冬酰胺合成酶基因表达的一个重要因素。
