Nitrogen is an essential core element in walnut seedling growth and development. However, nitrogen starvation and excessive nitrogen stress can cause stunted growth and development of walnut seedlings, and environmental pollution is also of concern. Therefore, it is necessary to study the mechanism of walnut seedling resistance to nitrogen stress. In this study, morphological and physiological observations and transcriptome sequencing of walnut seedlings under nitrogen starvation and excess nitrogen stress were performed. The results showed that walnut seedlings under nitrogen starvation and excess stress could adapt to the changes in the nitrogen environment by changing the coordination of their root morphology and physiological indexes. Based on an analysis of transcriptome data, 4911 differential genes (DEGs) were obtained (2180 were upregulated and 2731 were downregulated) in a comparison of nitrogen starvation and control groups. A total of 9497 DEGs (5091 upregulated and 4406 downregulated) were obtained in the comparison between the nitrogen overdose and control groups. When these DEGs were analysed, the differential genes in both groups were found to be significantly enriched in the plant’s circadian pathway. Therefore, we selected the circadian rhythm as the focus for further analysis. We made some discoveries by analysing the gene co-expression network of nitrogen metabolism, circadian rhythm, and hormone signal transduction. (a) Nitrite nitrogen (NO₂⁻) or Glu may act as a nitrogen signal to the circadian clock. (b) Nitrogen signalling may be input into the circadian clock by regulating changes in the abundance of the CRY1 gene. (c) After the nitrogen signal enters the circadian clock, the expression of the LHY gene is upregulated, which causes a phase shift in the circadian clock. (d) The RVE protein may send information about the circadian clock’s response to nitrogen stress back to the nitrogen metabolic pathway via the hormone transduction pathway. In conclusion, various metabolic pathways in the roots of walnut seedlings coordinated with one another to resist the ill effects of nitrogen stress on the root cells, and these coordination relationships were regulated by the circadian clock. This study is expected to provide valuable information on the circadian clock regulation of plant resistance to nitrogen stress.

氮素是核桃幼苗生长发育不可缺少的核心元素。但氮素缺乏和过度的氮胁迫会导致核桃幼苗生长发育迟缓，环境污染问题也值得关注。因此，有必要研究核桃幼苗抗氮胁迫的机制。本研究对氮饥饿和过量氮胁迫下核桃幼苗的形态生理学观察和转录组测序进行了研究。结果表明，氮饥饿和过度胁迫下的核桃幼苗可以通过改变其根系形态和生理指标的协调性来适应氮环境的变化。基于对转录组数据的分析，在氮饥饿组和对照组的比较中，获得了 4911 个差异基因 (DEG)（2180 个被上调，2731 个被下调）。在氮过量和对照组之间的比较中，总共获得了 9497 个 DEG（5091 个上调和 4406 个下调）。当分析这些DEG时，发现两组中的差异基因在植物的昼夜节律途径中显着富集。因此，我们选择昼夜节律作为进一步分析的重点。我们通过分析氮代谢、昼夜节律和激素信号转导的基因共表达网络取得了一些发现。(a) 亚硝酸盐氮 (NO 在氮过量和对照组之间的比较中，总共获得了 9497 个 DEG（5091 个上调和 4406 个下调）。当分析这些DEG时，发现两组中的差异基因在植物的昼夜节律途径中显着富集。因此，我们选择昼夜节律作为进一步分析的重点。我们通过分析氮代谢、昼夜节律和激素信号转导的基因共表达网络取得了一些发现。(a) 亚硝酸盐氮 (NO 在氮过量和对照组之间的比较中，总共获得了 9497 个 DEG（5091 个上调和 4406 个下调）。当分析这些DEG时，发现两组中的差异基因在植物的昼夜节律途径中显着富集。因此，我们选择昼夜节律作为进一步分析的重点。我们通过分析氮代谢、昼夜节律和激素信号转导的基因共表达网络取得了一些发现。(a) 亚硝酸盐氮 (NO 我们通过分析氮代谢、昼夜节律和激素信号转导的基因共表达网络取得了一些发现。(a) 亚硝酸盐氮 (NO 我们通过分析氮代谢、昼夜节律和激素信号转导的基因共表达网络取得了一些发现。(a) 亚硝酸盐氮 (NO₂ ^-) 或 Glu 可以作为生物钟的氮信号。(b) 氮信号可以通过调节 CRY1 基因丰度的变化输入到生物钟中。(c) 氮信号进入生物钟后，LHY基因的表达上调，导致生物钟发生相移。(d) RVE 蛋白可以通过激素转导途径将有关生物钟对氮胁迫的反应的信息发送回氮代谢途径。综上所述，核桃幼苗根系中多种代谢途径相互协调以抵抗氮胁迫对根细胞的不良影响，这些协调关系受生物钟的调控。