The Key Laboratory of Plant-Soil Interactions, MOE, Beijing, 100193, China.
Department of Plant Nutrition, China Agricultural University, Beijing, 100193, China.
Planta. 2020 Feb 17;251(3):66. doi: 10.1007/s00425-020-03363-9.
Glutamine (Gln) is an efficient nitrogen source in promoting aboveground nitrogen and biomass accumulation in ZD958 (an elite maize hybrid with great potential for further genetic improvement) seedlings when conditioning a smaller but adequate root system. Amino acids account for a significant part of nitrogen (N) resources in the soil. However, how amino acid-N affects crop growth remains to be further investigated. Here, glutamine (Gln) application (80% NHNO + 20% Gln; mixed N) enhanced shoot growth of the maize hybrid ZD958. N concentration in the shoot increased, which is associated with favorable increases in SPAD values, GS/GOGAT activities, and accumulation of glutamate, asparagine, total free amino acids and soluble proteins in the shoot under mixed N. On the other hand, root growth was reduced when exposed to Gln as indicated by the significantly lower dry weight, root/shoot ratio, and primary, seminal, crown, and total root lengths, as well as unfavorable physiological alterations. Up-regulation of expression of ZmAMT1.3, ZmNRT2.1, and ZmAAP2 in the root and that of ZmAMT1.1, ZmAMT1.3, and ZmLHT1 in the shoot preconditioned N over-accumulation in the shoot and facilitated shoot growth, presumably via enhancing N translocation to the shoot, when Gln was supplied. Together, Gln is an efficient N source in promoting aboveground N and biomass accumulation in ZD958 seedlings when conditioning a smaller but adequate root system. Notably, ZD958's parental lines Z58 and Chang7-2 displayed a wide range of variations in Gln responses, which may be partially attributed to single nucleotide polymorphisms (SNPs) in cis-elements and coding regions revealed in this study and much larger quantities of unidentified genetic variations between Z58 and Chang7-2. Extensive genetic divergence of these two elite inbred lines implied large potentials for further genetic improvement of ZD958 in relation to organic N use efficiency.
谷氨酰胺（Gln）是一种有效的氮源，可在调节较小但足够根系的同时，促进 ZD958（一种具有进一步遗传改良潜力的优秀玉米杂交种）幼苗地上部氮素和生物量的积累。氨基酸占土壤氮（N）资源的很大一部分。然而，氨基酸-N 如何影响作物生长仍有待进一步研究。在这里，谷氨酰胺（Gln）的应用（80%NHNO + 20%Gln；混合 N）增强了玉米杂交种 ZD958 的地上部生长。地上部的 N 浓度增加，这与 SPAD 值、GS/GOGAT 活性以及谷氨酸、天冬酰胺、总游离氨基酸和可溶性蛋白质在混合 N 下地上部的有利积累有关。另一方面，当暴露于 Gln 时，根生长受到抑制，表现为地上部干重、根/地上部比以及初生、次生根、冠根和总根长显著降低，以及不利的生理变化。在根中，ZmAMT1.3、ZmNRT2.1 和 ZmAAP2 的表达上调，在地上部中，ZmAMT1.1、ZmAMT1.3 和 ZmLHT1 的表达上调，这表明在 Gln 供应时，N 过量积累在地上部并促进地上部生长，可能是通过增强 N 向地上部的转运。总的来说，当调节较小但足够的根系时，Gln 是促进 ZD958 幼苗地上部 N 和生物量积累的有效氮源。值得注意的是，ZD958 的亲本系 Z58 和 Chang7-2 在 Gln 反应方面表现出广泛的变化，这可能部分归因于本研究中揭示的顺式元件和编码区的单核苷酸多态性（SNP），以及 Z58 和 Chang7-2 之间大量未识别的遗传变异。这两个优秀自交系的广泛遗传差异意味着 ZD958 在有机 N 利用效率方面有进一步遗传改良的巨大潜力。
