Mevalonate pyrophosphate decarboxylase is a kind of key enzyme in the terpenoid synthesis pathway in Eleutherococcus senticosus. The results of bisulfite sequencing showed that there were three kinds of samples with a low (0.68%), medium (0.72%) and high (0.79%) DNA methylation ratio in the promoter of MDD in E. senticosus, respectively. The transcriptome sequencing results showed that the expression of MDD in E. senticosus was significantly up-regulated in the types with low DNA methylation ratios of MDD (P < 0.05). There was a significant negative correlation between the saponin content in E. senticosus and the DNA methylation ratio of MDD promoter (P < 0.05). The screening results of differentially expressed transcription factors among the three groups with different DNA methylation ratio showed that a total of 4 transcription factors could bind to 6 CpG sites. Protein-protein interaction analysis showed that E. senticosus MDD could interacted with other key enzymes in the process of terpenoid synthesis. In addition, it was found that the DNA methylation of MDD promoter was mainly regulated by DNA methyltransferase. These results demonstrated that under the action of DNA methyltransferase, the changes of DNA methylation of MDD promoter could regulate its own expression level by affecting the combination ability of transcription factors, and then affected the expression of other genes in terpenoid synthesis pathway. The synthesis and accumulation of saponins in E. senticosus was also changed.

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Eupatorium adenophorum (Crofton weed) is an invasive weed in more than 30 countries. It inhibits the growth of surrounding plants by releasing allelochemicals during its invasion. However, the synthetic pathways and molecular mechanisms of its allelochemicals have been rarely reported. In this study, the related genes and pathways of allelochemicals in E. adenophorum were analyzed. Transcriptome analysis showed that differentially expressed genes (DEGs) were mainly enriched in the phenylpropanoid biosynthetic pathway and flavonoid biosynthetic pathway. Thirty-three DEGs involved in the synthesis of allelochemicals were identified, and 30 DEGs showed significant differences in blades and stems. Six allelochemicals were identified from blades and stems by ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Correlation analysis of genes and metabolites showed a strong correlation between the five genes and allelochemicals. In addition, this study supplemented the biosynthetic pathway of Eupatorium adenophorum B (HHO). It was found that acyclic sesquiterpene synthase (NES), δ-cadinene synthase (TPS), and cytochrome P450 (P450) were involved in the synthesis of HHO. These findings provide a dynamic spectrum consisting of allelochemical metabolism and a coexpression network of allelochemical synthesis genes in E. adenophorum .

Background Methyl-binding domain (MBD) is a class of methyl-CpG-binding domain proteins that affects the regulation of gene expression through epigenetic modifications. MBD genes are not only inseparable from DNA methylation but have also been identified and validated in various plants. Although MBD is involved in a group of physiological processes and stress regulation in these plants, MBD genes in Eleutherococcus senticosus remain largely unknown. Results Twenty EsMBD genes were identified in E. senticosus. Among the 24 chromosomes of E. senticosus, EsMBD genes were unevenly distributed on 12 chromosomes, and only one tandem repeat gene existed. Collinearity analysis showed that the fragment duplication was the main motif for EsMBD gene expansion. As the species of Araliaceae evolved, MBD genes also evolved and gradually exhibited different functional differentiation. Furthermore, cis-acting element analysis showed that there were numerous cis-acting elements in the EsMBD promoter region, among which light response elements and anaerobic induction elements were dominant. The expression motif analysis revealed that 60% of the EsMBDs were up-regulated in the 30% water content group. Conclusions By comparing the transcriptome data of different saponin contents of E. senticosus and integrating them with the outcomes of molecular docking analysis, we hypothesized that EsMBD2 and EsMBD5 jointly affect the secondary metabolic processes of E. senticosus saponins by binding to methylated CpG under conditions of drought stress. The results of this study laid the foundation for subsequent research on the E. senticosus and MBD genes.

Lithocarpus polystachyus Rehd has received great attention because of its pharmacological activities, such as inhibiting oxidation and lowering blood glucose and blood pressure, and flavonoids are one of its main pharmacodynamic components. It is important to understand the mechanisms of the flavonoid biosynthetic pathway of L. polystachyus , but the regulation of flavonoid biosynthesis is still unclear. In this study, differentially expressed genes and differentially accumulated metabolites in L. polystachyus were studied by integrating transcriptomics and metabolomics technologies. We confirmed the key genes involved in the flavonoid biosynthesis of L. polystachyus , including LpPAL3 , LpCHS1 , LpCHS2 , LpCHI2 , and LpF3H , which had consistent expression patterns with their upstream and downstream metabolites, and there is a significantly positive correlation between them. Compared to mature leaves, stems and young leaves are higher in the expression levels of key structural genes. We deduced that the MYB and bHLH transcription factors regulated the biosynthesis of different flavonoid metabolites and their regulatory patterns. Among them, LpMYB2 , LpMYB20 , LpMYB54 , LpMYB12 , and LpWD40-113 positively regulated the biosynthesis of flavones and flavanones. This discovery preliminarily revealed the pathways and key genes of flavonoid biosynthesis in L. polystachyus , which provided a reference for further study on flavonoid biosynthesis.