Flavonoids are phytochemicals present in medicinal plants and contribute to human health. Coreopsis tinctoria, a species rich in flavonoids, has long been used in traditional medicine and as a food resource. N (nitrogen) fertilization can reduce flavonoid accumulation in C. tinctoria. However, there is limited knowledge regarding N regulatory mechanisms. The aim of this study was to determine the effect of N availability on flavonoid biosynthesis in C. tinctoria and to investigate the relationship between C (carbon) and N metabolism coupled with flavonoid synthesis under controlled conditions. C. tinctoria seedlings were grown hydroponically under five different N levels (0, 0.625, 1.250, 2.500 and 5.000 mM). The related indexes of C, N and flavonoid metabolism of C. tinctoria under N variation were measured and analysed. N availability (low and moderate N levels) regulates enzyme activities related to C and N metabolism, promotes the accumulation of carbohydrates, reduces N metabolite levels, and enhances the internal C/N balance. The flavonoid content in roots and stalks remained relatively stable, while that in leaves peaked at low or intermediate N levels. Flavonoids are closely related to phenylalanine ammonia-lyase (PAL), cinnamate 4-hydroxylase (C4H), 4-coumarate: coenzyme A ligase (4CL), and chalcone-thioase (CHS) activity, significantly positively correlated with carbohydrates and negatively correlated with N metabolites. Thus, C and N metabolism can not only control the distribution of C in amino acid and carbohydrate biosynthesis pathways but also change the distribution in flavonoid biosynthesis pathways, which also provides meaningful information for maintaining high yields while ensuring the nutritional value of crop plants.

Nitrogen (N) deficiency levels were investigated for their potential to maintain the yield and improve antioxidant activity of Coreopsis tinctoria. Inflorescences and leaves at 0, 10, 20, 30, 40, and 50 d after flowering were frozen at −80 °C and plant growth, antioxidant activity, bioactive substance, enzyme activity, and gene expression were evaluated. N deficiency maintained the total number of flowers, promoted phenol and flavonoid accumulation, and enhanced antioxidant activity. Moreover, N deficiency stimulated activities of phenylalanine ammonia-lyase (PAL), cinnamate-4-hydroxylase (C4H) and 4-coumarate:coenzyme A ligase (4CL), and induced CtPAL, CtC4H and Ct4CL gene expression. The data also suggest that N-deficiency-induced phenolic and flavonoid accumulation occurs due to the activation of biosynthetic pathways in C. tinctoria. We characterize the unique features of C. tinctoria under N-deficiency conditions and provide valuable information for the cultivation of high-N use efficiency varieties with low input and high output.

Coreopsis tinctoria Nutt. ( C. tinctoria ) is used in composite tea material and has important medicinal functions. Soil salinization affects the growth and development of C. tinctoria in Xinjiang (China). Here, we discussed the changes in photosynthesis and physiological characteristics of C. tinctoria seedlings treated with different concentrations of NaCl [0 (CK), 50, 100, 150, 200, and 250 mmol·L ⁻¹ ] for 12, 24, and 72 hours. The results showed that the net photosynthetic rate (P _n ), stomatal conductance ( g _S ), transpiration rate (T _r ), and stomatal inhibition rate (L _s ) decreased significantly with increasing concentrations of NaCl. Salt stress promoted the accumulation of peroxidase (POD), catalase (CAT), soluble sugar, soluble protein, and free proline (Pro). A highly significant positive correlation was found between L _s and F _v /F _m ; L _s and F _v /F _o ; soluble sugar and CAT; soluble sugar and soluble protein. C. tinctoria was most sensitive to the concentrations of 150 to 250 mmol·L ⁻¹ NaCl, and its salt stress tolerance was increased by reducing photosynthetic fluorescence parameters, improving the antioxidant enzyme system, and regulating osmotic substances.

Coreopsis tinctoria Nutt. (C. tinctoria) has a long history of application and high economic and medicinal value. Flavonoids, the main active components of C. tinctoria, are widely studied in pharmacology and food development. However, the flavonoid biosynthesis pathway in C. tinctoria is unclear. In this study, we comprehensively compared the transcriptomes and metabolite profiles of two colors of C. tinctoria flowers (LS and JS) at different flowering stages. A total of 165 flavonoids (46 flavonoids, 42 flavonols, 22 anthocyanins, 18 chalcones, 12 dihydroflavonols, nine isoflavones, eight dihydroflavonoids, six flavanols, and two tannins) were identified in LS and JS at different flowering stages. Thirty-three metabolites (11 anthocyanins, 11 flavonols, seven flavonoids, two dihydroflavonols, one dihydroflavone, and one chalcone) were found to be statistically significantly different in the LS vs. JS groups. LS flowers accumulated higher levels of 10 anthocyanins (seven cyanidins and three pelargonidins) than JS flowers. Furthermore, candidate genes related to the regulation of flavonoid and anthocyanin synthesis were identified and included 28 structural genes (especially F3H, Cluster-28756.299649, and 3GT, Cluster-28756.230942) in LS and JS, six key differentially expressed transcription factors (especially MYB90a, Cluster-28756.143139) in LS and JS, and 17 other regulators (mainly including transporter proteins and others) in LS. Our results provide valuable information for further studies on the mechanism underlying flavonoid biosynthesis in C. tinctoria.

As natural environments degrade and extreme weather events become more frequent, humanity increasingly faces the challenge of producing crops under various complex and adverse conditions. Improving crop adaptability has become crucial. Universal stress proteins (USPs) are a class of small molecular proteins widely found in plants, capable of withstanding various biotic and abiotic environmental stresses, including temperature stress, drought, nutrient deficiency, oxidative imbalance, salt and heavy ion toxicity, and pathogenic infections. Enhancing our understanding of USPs holds significant potential for improving plant stress resilience. This study focuses on 13 species of Solanum, including cultivated and wild tomatoes, and systematically identified 438 members of the USP gene family through bioinformatics approaches. Phylogenetic analysis reveals that major USP members are conserved within Solanum, with interspecies differences in USP numbers primarily attributed to copy number variation (CNV). Through synteny and homology analyses, we found that USP27 and USP28 are unique to tomatoes, while the homologous gene of USP19 is absent in cultivated tomatoes. Notably, five unique USP genes are present in S. pennellii, which is characterized by its early differentiation and resistance advantages. Ka/Ks analysis indicates that only the USP10/21 homologous gene pair has undergone positive selection in wild tomatoes, while all other genes are subject to strong negative selection. The USPs in Solanum exhibit high consistency in domain characteristics, sequence conservation, and types of promoter regulatory elements, although there are substantial differences in the number of these elements. Utilizing publicly available data, we identified eight USPs that have undergone domestication or improvement selection, particularly noting the tissue-specific expression patterns of domesticated SolycUSP3/28/30. Through graph pangenome analysis, we screened 12 USPs covered by high-confidence structural variants, which primarily disrupt the intron regions of USPs, leading to significant differences in their expression responses to salt stress. We anticipate that these findings will provide a theoretical foundation and prior knowledge for further understanding and application of USP in plants.