Nitrate is the main nitrogen source for plant growth and development. Increasing evidence indicates that nitrate plays an important role in root growth and development. However, the effects of different concentrations of nitrate on the physiological and transcriptional response of soybean [Glycine max (L.) Merr.] root development at the seedling stage are not well understood. In this study, we found that both high and low concentrations of nitrate inhibited the growth and development of the soybean root system compared with optimal nitrate supply at the seedling stage. Using transcriptome sequencing technology, we identified 1,654, 1,283, and 2,083 significantly differentially expressed genes in soybean root grown under the low nitrate concentration, optimal nitrate concentration, and high nitrate concentration conditions, respectively. These genes were enriched in the Gene Ontology terms of metabolic process, catalytic activity, and membrane. The genes enriched in the pentose and glucuronate interconversions and glutathione metabolism pathways may play important roles during soybean root response to different concentrations of nitrate. In addition, the expression of 18 nitrate transporter genes changed significantly under different nitrate concentrations. Among them, the expression of two GmNPF6.3 genes was upregulated under the NL condition but downregulated under the NH condition, whereas six GmNPF7.3 genes exhibited opposite expression patterns. Taken together, our physiological data can enable a better understanding of the soybean root response under different nitrate concentrations, and the transcriptome data provide a list of candidate genes for further investigation of the mechanisms of root response under different nitrate concentrations.

中文翻译：

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大豆幼苗根部对不同硝酸盐水平的生理和转录组学响应

硝酸盐是植物生长发育的主要氮源。越来越多的证据表明硝酸盐在根系生长发育中起着重要作用。但不同浓度硝酸盐对大豆生理和转录反应的影响[ Glycine max (L.) Merr.] 幼苗阶段的根发育尚不清楚。在这项研究中，我们发现与幼苗期的最佳硝酸盐供应相比，高浓度和低浓度的硝酸盐都会抑制大豆根系的生长和发育。使用转录组测序技术，我们分别在低硝酸盐浓度、最佳硝酸盐浓度和高硝酸盐浓度条件下生长的大豆根中鉴定了 1,654、1,283 和 2,083 个显着差异表达的基因。这些基因在代谢过程、催化活性和膜的基因本体论术语中得到了丰富。富含戊糖和葡萄糖醛酸相互转化以及谷胱甘肽代谢途径的基因可能在大豆根系对不同浓度硝酸盐的反应过程中发挥重要作用。此外，18个硝酸盐转运蛋白基因的表达在不同硝酸盐浓度下发生显着变化。其中，两种表达方式GmNPF6.3基因在 NL 条件下上调，但在 NH 条件下下调，而六个GmNPF7.3基因表现出相反的表达模式。综上所述，我们的生理数据可以更好地了解不同硝酸盐浓度下大豆根的反应，转录组数据为进一步研究不同硝酸盐浓度下的根反应机制提供了候选基因列表。