Background Dendrobium officinale, an endangered Chinese herb, possesses extensive therapeutic effects and contains bioactive ingredients such as major polysaccharides, alkaloids, and minimal flavonoids. We first obtained the protocorm-like bodies (PLBs) of this plant through tissue culture in order to determine the distribution of the main secondary metabolites in each organelle and the PLBs. We then analyzed the correlation between gene expression level from comparative transcriptome sequencing and metabolite content in different organs to identify putative genes encoding enzymes involved in the biosynthesis of polysaccharides, alkaloids, and flavonoids. Results We used seeds as explants for protocorm induction and PLB propagation of D. officinale. The optimal medium formula for PLB propagation was 1/2 MS + α-NAA 0.5 mg·L− 1 + 6-BA 1.0 mg·L− 1 + 2, 4-D 1.5–2.0 mg·L− 1 + potato juice 100 g·L− 1. Stems, PLBs and leaves of D. officinale had the highest content of polysaccharides, alkaloids and flavonoids, respectively. Naringenin was only produced in stem; however, PLBs with high alkaloid content can replace other organs producing alkaloids. The hot water extraction method outperformed the ultrasound-assisted extraction method for extracting polysaccharides from D. officinale. A comparative transcriptome analysis of PLBs and leaves of D. officinale revealed differential expression of genes encoding enzymes involved in polysaccharide, alkaloid and flavonoid biosynthetic pathways. Putative genes encoding enzymes involved in these biosynthetic pathways were identified. Notably, we identified genes encoding the alkaloid biosynthesis enzymes strictosidine β-D-Glucosidase, geissoschizine synthase and vinorine synthase in D. officinale. Conclusions The identification of candidate genes encoding enzymes involved in metabolite biosynthesis will help to explore and protect this endangered species and facilitate further analysis of the molecular mechanism of secondary metabolite biosynthesis in D. officinale.
Platycodin D and platycoside E are two triterpenoid saponins in Platycodon grandiflorus, differing only by two glycosyl groups structurally. Studies have shown β-Glucosidase from bacteria can convert platycoside E to platycodin D, indicating the potential existence of similar enzymes in P. grandiflorus. An L9(34) orthogonal experiment was performed to establish a protocol for calli induction as follows: the optimal explant is stems with nodes and the optimum medium formula is MS + NAA 1.0 mg/L + 6-BA 0.5 mg/L to obtain callus for experimental use. The platycodin D, platycoside E and total polysaccharides content between callus and plant organs varied wildly. Platycodin D and total polysaccharide content of calli was found higher than that of leaves. While, platycoside E and total polysaccharide content of calli was found lower than that of leaves. Associating platycodin D and platycoside E content with the expression level of genes involved in triterpenoid saponin biosynthesis between calli and leaves, three contigs were screened as putative sequences of β-Glucosidase gene converting platycoside E to platycodin D. Besides, we inferred that some transcription factors can regulate the expression of key enzymes involved in triterpernoid saponins and polysaccharides biosynthesis pathway of P. grandiflorus. Totally, a candidate gene encoding enzyme involved in converting platycoside E to platycodin D, and putative genes involved in polysaccharide synthesis in P. grandiflorus had been identified. This study will help uncover the molecular mechanism of triterpenoid saponins biosynthesis in P. grandiflorus.
The highly esteemed Chinese herb, Dendrobium huoshanense, whose major metabolites are polysaccharides and alkaloids, is on the verge of extinction. The stone planting under the forest (SPUF) and greenhouse planting (GP) of D. huoshanense are two different cultivation methods of pharmaceutical Dendrobium with significantly differences in morphology, metabolites content and composition, and medication efficacy. Here, we conducted proteomics and phosphoproteomics analyses to reveal differences in molecular mechanisms between SPUF and GP. We identified 237 differentially expressed proteins (DEPs) between the two proteomes, and 291 modification sites belonging to 215 phosphoproteins with a phosphorylation level significantly changed (PLSC) were observed. GO, KEGG pathway, protein domain, and cluster analyses revealed that these DEPs were mainly localized in the chloroplast; involved in processes such as posttranslational modification, carbohydrate transport and metabolism, and secondary metabolite biosynthesis; and enriched in pathways mainly including linoleic acid metabolism, plant-pathogen interactions, and phenylpropanoid, cutin, suberin, and wax biosynthesis. PLSC phosphoproteins were mainly located in the chloroplast, and highly enriched in responses to different stresses and signal transduction mechanisms through protein kinase and phosphotransferase activities. Significant differences between SPUF and GP were observed by mapping the DEPs and phosphorylated proteins to photosynthesis and polysaccharide and alkaloid biosynthesis pathways. Phosphorylation characteristics and kinase categories in D. huoshanense were also clarified in this study. We analyzed different molecular mechanisms between SPUF and GP at proteomic and phosphoproteomic levels, providing valuable information for the development and utilization of D. huoshanense.
Ginger (Zingiber officinale Roscoe) is an important plant used worldwide for medicine and food. The R2R3‐MYB transcription factor (TF) family has essential roles in plant growth, development, and stresses resistance, and the number of genes in the family varies greatly among different types of plants. However, genome‐wide discovery of ZoMYBs and gene responses to stresses have not been reported in ginger. Therefore, genome‐wide analysis of R2R3‐MYB genes in ginger was conducted in this study. Protein phylogenetic relations and conserved motifs and chromosome localization and duplication, structure, and cis‐regulatory elements were analyzed. In addition, the expression patterns of selected genes were analyzed under two different stresses. A total of 299 candidate ZoMYB genes were discovered in ginger. Based on groupings of R2R3‐MYB genes in the model plant Arabidopsis thaliana (L.) Heynh., ZoMYBs were divided into eight groups. Genes were distributed across 22 chromosomes at uneven densities. In gene duplication analysis, 120 segmental duplications were identified in the ginger genome. Gene expression patterns of 10 ZoMYBs in leaves of ginger under abscisic acid (ABA) and low‐temperature stress treatments were different. The results will help to determine the exact roles of ZoMYBs in anti‐stress responses in ginger.
Background: Zingiber officinale Roscoe (ginger), as a plant used for medicine and food, has a pivotal position all over the world. The R2R3-MYB transcription factor family is one of the largest, and it plays a significant role in plant growth, development, and stresses resistance. According to existing reports, the amounts of R2R3-MYB genes varies greatly among all kinds of plants. However, genome-wide discovery of ZoMYBs family and its corresponding stresses have not been reported in Z. officinale.Results: The genome-wide analysis of R2R3-MYB genes in Z. officinale was carried out in this study. Protein analysis included phylogenetic analysis and conserved motifs analysis, while gene analysis included chromosome localization and gene replication analysis, gene structure analysis, cis-regulatory element analysis and gene expression pattern analysis under two different stresses. A total of 299 candidate ZoMYB genes were discovered in Z. officinale. Based on the grouping of R2R3-MYB genes in a model plant Arabidopsis thaliana, ZoMYBs was divided into 8 groups and distributed across 22 chromosomes at uneven densities. Through gene duplication analysis, a total of 28 segmental duplication were identified in ginger genome. In addition, the expression pattern of 10 chosen ZoMYBs in leaves of Z. officinale were detected under ABA and low temperature stress treatments. The result revealed that there were differences in gene expression of these ten MYB genes in ginger under ABA treatment and low temperature treatment.Conclusions: Our results revealed the characteristics of ZoMYB genes family and provided valuable information for improving the ability of Z. officinale to cope with environmental changes during growth and development.
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