Regulation of the High-Affinity Nitrate Transport System in Wheat Roots by Exogenous Abscisic Acid and Glutamine

硝酸盐是为大多数庄稼的主要的氮(N) 来源。由根房间的硝酸盐举起是氮素代谢的一个关键步骤并且广泛地在生理、分子的层次被学习了。理解硝酸盐举起怎么被调整将帮助我们与改进硝酸盐举起效率设计庄稼。现在的学习在小麦(Triticum aestivum L.) 由外长的 abscisic 酸(骆驼毛的织物) 和夫酸安(Gln ) 调查了高亲密关系的硝酸盐运输系统(帽子) 的规定根。在作为唯一的氮包含 2 mmol/L 硝酸盐的营养液种的小麦幼苗采购原料因为 2 个星期为 4 d 被剥夺 N 并且然后为 0 被转移到当面包含 50 omol/L 骆驼毛的织物，和 1 mmol/L Gln 的营养液或 2 mmol/L 硝酸盐的缺席， 0.5 ， 1 ， 2 ， 4 ，和 8 h 。对待的小麦植物然后被划分成二个组。一个组植物被用来调查在通过半量的 RT-PCR 的根的 NRT2 和 NAR2 基因接近的帽子部件的信使 rna 层次，并且其它植物设定被用来在包含 0.2 mmol/L 的营养液测量高亲密关系的硝酸盐流入率标记 p#eN 的硝酸盐。结果证明当硝酸盐不是在营养液的现在，但是进一步没由硝酸盐提高这些基因的正式就职时，那件外长的骆驼毛的织物在根导致了 TaNRT2.1， TaNRT2.2， TaNRT2.3， TaNAR2.1，和 TaNAR2.2 基因的表示。夫酸安，当硝酸盐在生长媒介是在场的时，被显示了禁止 NRT2 基因的表示，没禁止这正式就职。当 Gln 被供应到没有硝酸盐的营养液时，在根的这五基因的表示被导致。仅仅当硝酸盐在生长媒介是在场的时，这些结果暗示由 NRT2 表示的 Gln 的抑制发生。尽管外长的骆驼毛的织物和 Gln 在小麦的根导致了帽子基因，他们没导致硝酸盐流入。

Nitrate is a major nitrogen （N） source for most crops. Nitrate uptake by root cells is a key step of nitrogen metabolism and has been widely studied at the physiological and molecular levels. Understanding how nitrate uptake is regulated will help us engineer crops with improved nitrate uptake efficiency. The present study investigated the regulation of the high-affinity nitrate transport system （HATS） by exogenous abscisic acid （ABA） and glutamine （Gin） in wheat （Triticum aestivum L.） roots. Wheat seedlings grown in nutrient solution containing 2 mmol/L nitrate as the only nitrogen source for 2weeks were deprived of N for 4d and were then transferred to nutrient solution containing 50 μmol/L ABA, and 1 mmol/L Gin in the presence or absence of 2 mmol/L nitrate for 0, 0.5, 1, 2, 4, and 8 h. Treated wheat plants were then divided into two groups. One group of plants was used to investigate the mRNA levels of the HATS components NRT2 and NAR2 genes in roots through semi-quantitative RT-PCR approach, and the other set of plants were used to measure high-affinity nitrate influx rates in a nutrient solution containing 0.2 mmol/L ^15N-labeled nitrate. The results showed that exogenous ABA induced the expression of the TaNRT2.1, TaNRT2.2, TaNRT2.3, TaNAR2.1, and TaNAR2.2 genes in roots when nitrate was not present in the nutrient solution, but did not further enhance the induction of these genes by nitrate. Glutamine, which has been shown to inhibit the expression of NRT2 genes when nitrate is present in the growth media, did not inhibit this induction. When Gin was supplied to a nitrate-free nutrient solution, the expression of these five genes in roots was induced. These results imply that the inhibition by Gin of NRT2 expression occurs only when nitrate is present in the growth media. Although exogenous ABA and Gin induced HATS genes in the roots of wheat, they did not induce nitrate influx.