Quinoa (Chenopodium quinoa) is an Andean allotetraploid pseudocereal crop with higher protein content and balanced amino acid composition in the seeds. Ammonium (NH₄⁺), a direct source of organic nitrogen assimilation, mainly transported by specific transmembrane ammonium transporters (AMTs), plays important roles in the development, yield, and quality of crops. Many AMTs and their functions have been identified in major crops; however, no systematic analyses of AMTs and their regulatory networks, which is important to increase the yield and protein accumulation in the seeds of quinoa, have been performed to date. In this study, the CqAMTs were identified, followed by the quantification of the gene expression, while the regulatory networks were predicted based on weighted gene co-expression network analysis (WGCNA), with the putative transcriptional factors (TFs) having binding sites on the promoters of CqAMTs, nitrate transporters (CqNRTs), and glutamine-synthases (CqGSs), as well as the putative TF expression being correlated with the phenotypes and activities of GSs, glutamate synthase (GOGAT), nitrite reductase (NiR), and nitrate reductase (NR) of quinoa roots. The results showed a total of 12 members of the CqAMT family with varying expressions in different organs and in the same organs at different developmental stages. Complementation expression analyses in the triple mep1/2/3 mutant of yeast showed that except for CqAMT2.2b, 11/12 CqAMTs restored the uptake of NH₄⁺ in the host yeast. CqAMT1.2a was found to mainly locate on the cell membrane, while TFs (e.g., CqNLPs, CqG2Ls, B3 TFs, CqbHLHs, CqZFs, CqMYBs, CqNF-YA/YB/YC, CqNACs, and CqWRKY) were predicted to be predominantly involved in the regulation, transportation, and assimilation of nitrogen. These results provide the functions of CqAMTs and their possible regulatory networks, which will lead to improved nitrogen use efficiency (NUE) in quinoa as well as other major crops.

Stephania epigaea, an important traditional folk medicinal plant, elucidating its bioactive compound profiles and their molecular mechanisms of action on human health, would better understand its traditional therapies and guide their use in preclinical and clinical. This study aims to detect the critical therapeutic compounds, predict their targets, and explore potential therapeutic molecular mechanisms. This work first determined metabolites from roots, stems, and flowering twigs of S. epigaea by a widely targeted metabolomic analysis assay. Then, the drug likeness of the compounds and their pharmacokinetic profiles were screened by the ADMETlab server. The target proteins of active compounds were further analyzed by PPI combing with GO and KEGG cluster enrichment analysis. Finally, the interaction networks between essential compounds, targets, and disease-associated pathways were constructed, and the essential compounds binding to their possible target proteins were verified by molecular docking. Five key target proteins (EGFR, HSP90AA1, SRC, TNF, and CASP3) and twelve correlated metabolites, including aknadinine, cephakicine, homostephanoline, and N-methylliriodendronine associated with medical applications of S. epigaea, were identified, and the compounds and protein interactions were verified. The key active ingredients are mainly accumulated in the root, which indicates that the root is the main medicinal tissue. This study demonstrated that S. epigaea might exert the desired disease efficacy mainly through twelve components interacting via five essential target proteins. EGFR is the most critical one, which deserves further verification by biological studies.

Nitrogen application rate and topping are two key agronomic factors affecting tobacco leaf quality, but the synergistic regulatory mechanisms remain unclear. This study aimed to elucidate the physiological and molecular mechanisms by which nitrogen application rate and topping synergistically regulate tobacco leaf quality, and to identify key candidate genes involved in nicotine biosynthesis. Using the tobacco cultivar K326, three nitrogen application levels were established: low (0 kg/ha), medium (120 kg/ha), and high (210 kg/ha). Agronomic traits and rhizosphere soil physicochemical properties were monitored, carbon and nitrogen metabolism enzyme activities were measured before and after topping, and mature leaf chemical composition was determined, integrated with transcriptomic and metabolomic analyses. The results showed that medium nitrogen achieved high yield while enhancing organic matter turnover efficiency, reducing rhizosphere water-soluble chloride content, and alleviating soil acidification and ammonium–potassium ion uptake competition caused by excessive fertilization. Combined with topping, it significantly enhanced carbon and nitrogen metabolism, promoted starch-to-soluble-sugar conversion, and increased nicotine accumulation, thereby optimizing leaf chemical composition. Integrated transcriptomic and metabolomic analyses revealed that medium nitrogen combined with topping exerted the most pronounced effects on gene expression and metabolite accumulation. Weighted gene co-expression network analysis (WGCNAs) identified a module highly correlated with nicotine biosynthesis, with hub genes mainly annotated as cytochrome P450 and terpene synthase family members. In conclusion, this study elucidated the molecular mechanisms by which the combination of medium nitrogen application and topping, as an integrated agronomic practice, improves tobacco leaf quality through coordinating carbon-nitrogen metabolism and optimizing chemical composition, and identified key candidate genes potentially regulating nicotine biosynthesis, providing a theoretical basis for nitrogen fertilizer management and high-quality cultivation of tobacco.