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Abstract：
Foxtail millet (Setaria italica (L.) P. Beauv) is an important food and forage crop that is well adapted to nutrient-poor soils. However, our understanding of how different LN-tolerant foxtail millet varieties adapt to long-term low nitrogen (LN) stress at the physiological and molecular levels remains limited. In this study, two foxtail millet varieties with contrasting LN tolerance properties were investigated through analyses of physiological parameters and transcriptomics. The physiological results indicate that JG20 (high tolerance to LN) exhibited superior biomass accumulation both in its shoots and roots, and higher nitrogen content, soluble sugar concentration, soluble protein concentration, zeatin concentration in shoot, and lower soluble sugar and soluble protein concentration in its roots compared to JG22 (sensitive to LN) under LN, this indicated that the LN-tolerant foxtail millet variety can allocate more functional substance to its shoots to sustain aboveground growth and maintain high root activity by utilizing low soluble sugar and protein under LN conditions. In the transcriptomics analysis, JG20 exhibited a greater number of differentially expressed genes (DEGs) compared to JG22 in both its shoots and roots in response to LN stress. These LN-responsive genes were enriched in glycolysis metabolism, photosynthesis, hormone metabolism, and nitrogen metabolism. Furthermore, in the shoots, the glutamine synthetase gene SiGS5, chlorophyll apoprotein of photosystem II gene SiPsbQ, ATP synthase subunit gene Sib, zeatin synthesis genes SiAHP1, and aldose 1-epimerase gene SiAEP, and, in the roots, the high-affinity nitrate transporter genes SiNRT2.3, SiNRT2.4, glutamate synthase gene SiGOGAT2, fructose-bisphosphate aldolase gene SiFBA5, were important genes involved in the LN tolerance of the foxtail millet variety. Hence, our study implies that the identified genes and metabolic pathways contribute valuable insights into the mechanisms underlying LN tolerance in foxtail millet.
摘要：
谷子(Setariaitalica(L.）P.Beauv）是一种重要的食品和饲料作物，非常适合营养贫瘠的土壤。然而,我们对不同的耐LN谷子品种如何在生理和分子水平上适应长期低氮（LN）胁迫的理解仍然有限。在这项研究中,通过生理参数和转录组学分析，研究了两个具有不同LN耐性的谷子品种。生理结果表明，JG20（对LN的高耐受性）在其芽和根中都表现出优异的生物量积累。和更高的氮含量，可溶性糖浓度，可溶性蛋白质浓度，芽中的玉米素浓度，与LN下的JG22（对LN敏感）相比，其根部的可溶性糖和可溶性蛋白质浓度较低，这表明耐LN谷子品种在LN条件下利用低可溶性糖和蛋白质，可以在其芽中分配更多的功能物质，以维持地上生长并保持较高的根系活性。在转录组学分析中，与JG22相比，JG20在其对LN胁迫的反应中在其芽和根中表现出更多的差异表达基因（DEG）。这些LN反应基因在糖酵解代谢中富集，光合作用,激素代谢，和氮代谢。此外，在拍摄中，谷氨酰胺合成酶基因SiGS5，光系统II基因SiPsbQ的叶绿素载脂蛋白，ATP合酶亚基基因Sib,玉米素合成基因SiAHP1和醛糖1-差向异构酶基因SiAEP，and,在根部，高亲和力硝酸盐转运蛋白基因SiNRT2.3，SiNRT2.4，谷氨酸合酶基因SiGOGAT2，果糖-二磷酸醛缩酶基因SiFBA5是参与谷子品种LN耐受性的重要基因。因此，我们的研究表明，已确定的基因和代谢途径对谷子LN耐受性的潜在机制提供了有价值的见解。
