Cyclocaryapaliurus leaves are rich in triterpenoids with positive results in the treatment of diabetes, antioxidation, and scavenging free radicals. C. paliurus red leaves have been found to contain higher flavonoids including anthocyanin, however, the triterpenoids accumulation pattern is still unclear. For the purpose of researching the triterpenoid accumulating mechanism during red new leaf development, transcriptome and metabolome analysis was conducted during C. paliurus the red leaf development process. The results uncovered that most triterpenoid ingredients were found to accumulate during leaves turning green, while the unique ingredients content including cyclocaric acid A, cyclocarioside I, cyclocarioside Ⅱand cyclocarioside Ⅲ decreased or remained unchanged. Functional structure genes (hydroxymethylglutaryl-CoA synthase, hydroxymethylglutaryl-CoA reductase, and farnesyl-diphosphate synthase) were identified for promoting triterpenoids accumulation mainly in the mevalonic acid pathway (MVA). Moreover, glycosyltransferase (UGT73C, UGT85A, and UGT85K) was also found attributed to triterpenoids accumulation. These findings provide information for a better understanding of the triterpenoid biosynthesis mechanism during leaf development and will be useful for targeted breeding.

Cyclocarya paliurus, endemic to the subtropical regions of southern China, holds significant potential as a health product, with its leaf-derived secondary metabolites commanding considerable value. This study aimed to investigate the secondary metabolites associated with graft success in C. paliurus by selecting three clones and three provenances as grafting scions and rootstocks. The survival rates of various graft combinations were meticulously recorded. Targeted metabolic profiling of the graft union was employed to analyze the flavonoid and phenylpropanoid biosynthesis pathways in both compatible and incompatible graft combinations. The results indicate that phenylpropanoids preferentially accumulate in compatible graft unions, while flavonoids are more abundant in incompatible unions. In the grafted seedlings of C. paliurus, ferulic acid, glycitein, dihydromyricetin, pinocembrin, and apigenin exhibited distinct accumulation patterns. These findings revealed the regulatory patterns within the phenylpropanoid biosynthesis pathway for predicting graft success in C. paliurus. The insights are valuable for the optimization of C. paliurus grafting practices and for future breeding programs aimed at enhancing the species’ horticultural and economic potential.

Secondary metabolites in Cyclocarya paliurus (Batalin) Iljinsk. leaves are beneficial for human health. The synthesis and accumulation of secondary metabolites form a complex process that is influenced by the trade-off between primary and secondary metabolism and by the biosynthetic pathways themselves. In this study, we explored the relationship between secondary metabolite accumulation and the activity of metabolic networks in leaves of C. paliurus. Leaves at three different growth stages were subjected to transcriptomic and non-targeted metabolomic analyses. The results revealed that nitrogen assimilation increased and carbon assimilation decreased as leaves matured, and the patterns of secondary metabolite accumulation and gene expression differed among the leaves at different growth stages. Mature green leaves had higher nitrogen assimilation and lower carbon assimilation, which were correlated with variations in secondary metabolite accumulation. As a major source of carbon and nitrogen, glutamine accumulated in the mature green leaves of C. paliurus. The accumulation of glutamine inhibited phenylalanine biosynthesis by modulating the pentose phosphate pathway but promoted acetyl-CoA biosynthesis through the tricarboxylic acid cycle. These changes led to decreased flavonoid contents and increased triterpenoid contents in mature leaves. These metabolomic and transcriptomic data reveal the differential expression of metabolic regulatory networks during three stages of leaf development and highlight the trade-off between primary and secondary metabolism. Our results provide a comprehensive picture of the metabolic pathways that are active in the leaves of C. paliurus at different growth stages.

The phenotypes of Sapindus are significantly influenced by environmental factors, but the responses of oil-related seed phenotypes to environmental factors are still unclear. We sampled 115 seed accessions of Sapindus mukorossi Gaertn. and 33 of Sapindus delavayi (Franch.) Radlk. from fifty-six distinct locations in China to explore the effects of environmental factors on the seed phenotypes. Pearson’s correlation analysis showed that 100-seed kernel weight (SKW), 100-seed shell weight (SSW), and seed kernel content (SKC) were the phenotypes most sensitive to the environmental influence (significantly associated with at least ten environmental factors). Redundancy analysis explained 26.13% of the variance and revealed that longitude was negatively correlated with SKW and SKC but was positively correlated with SSW, whereas elevation had the opposite effect. Monthly sunshine hours was negatively correlated with 100-seed weight and SSW. Additionally, the Mantel test showed that the seed phenotypic variations in Sapindus mukorossi and Sapindus delavayi were significantly affected by environmental factors differently. SKW and SKC of Sapindus delavayi were more sensitive to the influence of key environmental factors and therefore had more potential for oil development. It is recommended to cultivate Sapindus delavayi at lower longitudes to facilitate seed kernel development and promote oil yield. Study Implications: This study revealed the response pattern of the seed phenotypes of Sapindus mukorossi Gaertn. and Sapindus delavay (Franch.) Radlk. to environmental factors. Sapindus delavay had larger seed kernels and thinner seed shells, indicating a higher potential for oil production. At lower longitudes, the seed kernels of Sapindus are heavier, favoring kernel oil production, and the seed shells are lighter, which facilitates processing. This implied that growers can cultivate Sapindus in suitable climatic regions for commercial purposes such as oil production.

To reveal the effects of genotype–herbivore interactions on leaf quality, foliar variations in phytochemicals, morphoanatomy, and herbivory damage ratio were investigated in a Cyclocarya paliurus (Batalin) Iljinsk. (Juglandaceae) germplasm resources bank. Results showed less herbivory damage in genotypes with a higher leaf thickness, but more herbivory damage in genotypes with a higher leaf stomatal density. Herbivory damage ratios were significantly correlated with the contents of leaf secondary metabolites, whereas the response of secondary metabolites to insect attack was type-specific and varied between intact leaves and damaged leaves. Based on key indicators of leaf quality (contents of triterpenoids, flavonoids, polyphenols, pterocaryoside A, pterocaryoside B, and cyclocaric acid B), the investigated genotypes were divided into three distinct groups by integrating TOPSIS and cluster analysis, while four genotypes with slight insect damage demonstrated the prioritization for future applications. Our findings lay a foundation for further selection of its superior varieties with both insect resistance and high leaf quality.