Strictosidine-related enzymes involved in the alkaloid biosynthesis ofUncaria tomentosaroot cultures grown under oxidative stress

Induction of Monoterpenoid Oxindole Alkaloids Production and Related Biosynthetic Gene Expression in Response to Signaling Molecules in Hamelia patens Plant Cultures

Hamelia patens (Rubiaceae), known as firebush, is a source of bioactive monoterpenoid oxindole alkaloids (MOAs) derived from monoterpenoid indole alkaloids (MIAs). With the aim of understanding the regulation of the biosynthesis of these specialized metabolites, micropropagated plants were elicited with jasmonic acid (JA) and salicylic acid (SA). The MOA production and MIA biosynthetic-related gene expression were evaluated over time. The production of MOAs was increased compared to the control up to 2-fold (41.3 mg g DW-1) at 72 h in JA-elicited plants and 2.5-fold (42.4 mg g DW-1) at 120 h in plants elicited with SA. The increment concurs with the increase in the expression levels of the genes HpaLAMT, HpaTDC, HpaSTR, HpaNPF2.9, HpaTHAS1, and HpaTHAS2. Interestingly, it was found that HpaSGD was downregulated in both treatments after 24 h but in the SA treatment at 120 h only was upregulated to 8-fold compared to the control. In this work, we present the results of MOA production in H. patens and discuss how JA and SA might be regulating the central biosynthetic steps that involve HpaSGD and HpaTHAS genes.

Profiles of Metabolic Genes in Uncaria rhynchophylla and Characterization of the Critical Enzyme Involved in the Biosynthesis of Bioactive Compounds-(iso)Rhynchophylline

Rhynchophylline (RIN) and isorhynchophylline (IRN), two of the representative types of indole alkaloids, showed the unique spiroindole structures produced in Uncaria rhynchophylla. As the bioactive constituent of U. rhynchophylla, IRN has recently drawn extensive attention toward antihypertensive and neuroprotective activities. Despite their medicinal importance and unique chemical structure, the biosynthetic pathways of plant spiroindole alkaloids are still largely unknown. In this study, we used U. rhynchophylla, extensively used in traditional Chinese medicine (TCM), a widely cultivated plant of the Uncaria genus, to investigate the biosynthetic genes and characterize the functional enzymes in the spiroindole alkaloids. We aim to use the transcriptome platform to analyse the tissue-specific gene expression in spiroindole alkaloids-producing tissues, including root, bud, stem bark and leaf. The critical genes involved in the biosynthesis of precursors and scaffold formation of spiroindole alkaloids were discovered and characterized. The datasets from this work provide an essential resource for further investigating metabolic pathways in U. rhynchophylla and facilitate novel functional enzyme characterization and a good biopharming approach to spiroindole alkaloids.

Boosting of Antioxidants and Alkaloids in Catharanthus roseus Suspension Cultures Using Silver Nanoparticles with Expression of CrMPK3 and STR Genes

Global agricultural systems are under unprecedented pressures due to climate change. Advanced nano-engineering can help increase crop yields while ensuring sustainability. Nanotechnology improves agricultural productivity by boosting input efficiency and reducing waste. Alkaloids as one of the numerous secondary metabolites that serve variety of cellular functions essential for physiological processes. This study tests the competence of silver nanoparticles (AgNPs) in boosting alkaloids accumulation in Catharanthus roseus suspension cultures in relation to the expression of C. roseus Mitogen Activated Protein Kinase 3 (CrMPK3) and Strictosidine Synthase (STR) genes. Five concentrations (5, 10, 15, 20 and 25 mg·L-1) of AgNPs were utilized in addition to deionized water as control. Results reflected binary positive correlations among AgNPs concentration, oxidative stress indicated with increase in hydrogen peroxide and malondialdehyde contents, activities of ascorbate peroxidase and superoxide dismutase, expression of the regulatory gene CrMPK3 and the alkaloid biosynthetic gene STR as well as alkaloids accumulation. These correlations add to the growing evidence that AgNPs can trigger the accumulation of alkaloids in plant cells through a signaling pathway that involves hydrogen peroxide and MAPKs, leading to up-regulation of the biosynthetic genes, including STR gene.

Strictosidine synthase, an indispensable enzyme involved in the biosynthesis of terpenoid indole and β-carboline alkaloids

Terpenoid indole (TIAs) and β-carboline alkaloids (BCAs), such as suppressant reserpine, vasodilatory yohimbine, and antimalarial quinine, are natural compounds derived from strictosidine. These compounds can exert powerful pharmacological effects but be obtained from limited source in nature. the whole biosynthetic pathway of TIAs and BCAs, The Pictet-Spengler reaction catalyzed by strictosidine synthase (STR; EC: 4.3.3.2) is the rate-limiting step. Therefore, it is necessary to investigate their biosynthesis pathways, especially the role of STR, and related findings will support the biosynthetic generation of natural and unnatural compounds. This review summarizes the latest studies concerning the function of STR in TIA and BCA biosynthesis, and illustrates the compounds derived from strictosidine. The substrate specificity of STR based on its structure is also summarized. Proteins that contain six-bladed four-stranded β-propeller folds in many organisms, other than plants, are listed. The presence of these folds may lead to similar functions among organisms. The expression of STR gene can greatly influence the production of many compounds. STR is mainly applied to product various valuable drugs in plant cell suspension culture and biosynthesis in other carriers.

Effects of Concentration and Temperature of Nutrient Solution on Growth and Camptothecin Accumulation of Ophiorrhiza pumila

The medicinal plant, Ophiorrhiza pumila, naturally grows on the floors of humid inland forests in subtropical areas. It accumulates camptothecin (CPT), which is used as an anti-tumor agent, in all organs. We investigated the optimal hydroponic root-zone environments for growth and CPT accumulation in O. pumila in a plant factory. In experiment 1, to determine the appropriate nutrient solution concentration (NSC), O. pumila was cultivated using four concentrations (0.125, 0.25, 0.5, and 1.0 times) of a commercial solution for 63 days after the start of treatment (DAT). The electrical conductivity of these NSCs was 0.6, 0.9, 1.5, and 2.7 dS m⁻¹, respectively. The total dry weights at 0.25 and 0.5 NSCs were higher than those at the other two NSCs. CPT content at 0.25 NSC was significantly higher than those at other NSCs. In experiment 2, to investigate an appropriate nutrient solution temperature (NST), O. pumila was cultivated at four NSTs (10, 20, 26, and 35 °C, named as T10, T20, T26, and T36, respectively) for 35 DAT. The growth and CPT content at T20 was the highest among the treatments. Therefore, root-zone environments of 0.25 NSC and 20 °C of NST produced the best growth and CPT accumulation in O. pumila.

Glucoindole alkaloid accumulation induced by yeast extract in Uncaria tomentosa root cultures is involved in defense response

OBJECTIVE

To evaluate the induction of monoterpenoid indole alkaloids (MIA) and phenolic compound production by yeast extract (YE) and its relationship with defense responses in Uncaria tomentosa (Rubiaceae) root cultures.

RESULTS

Root cultures were elicited by YE at three concentrations. The 0.5 mg YE ml^-1 treatment did not affect cell viability but increased the hydrogen peroxide concentration by 5.7 times; guaiacol peroxidase activity by twofold; and the glucoindole alkaloid 3α-dihydrocadambine (DHC) content by 2.6 times (to 825.3 ± 27.3 μg g^-1). This treatment did not affect the contents of monoterpenoid oxindole alkaloids or chlorogenic acids. In response to 0.5 mg YE ml^-1 treatment, the transcript levels of MIA biosynthetic genes, TDC and LAMT, increased 5.4 and 1.9-fold, respectively, that of SGD decreased by 32%, and that of STR did not change. The transcript levels of genes related to phenolic compounds, PAL, CHS and HQT, increased by 1.7, 7.7, and 1.2-fold, respectively. Notably, the transcript levels of Prx1 and Prx encoding class III peroxidases increased by 1.4 and 2.5-fold.

CONCLUSION

The YE elicitor induced an antioxidant defense response, increased the transcript levels of genes encoding enzymes related to strictosidine biosynthesis precursors and class III peroxidases, and decreased the transcript level of SGD. Thus, YE could stimulate antifungal DHC production in root cultures of U. tomentosa.

Metabolic Profiling of Dendrobium officinale in Response to Precursors and Methyl Jasmonate

Alkaloids are the main active ingredients in the medicinal plant Dendrobium officinale. Based on the published genomic and transcriptomic data, a proposed terpenoid indole alkaloid (TIA) biosynthesis pathway may be present in D. officinale. In this study, protocorm-like bodies (PLBs) with a high-yielding production of alkaloids were obtained by the optimization of tryptophan, secologanin and methyl jasmonate (MeJA) treatment. The results showed that the total alkaloid content was 2.05 times greater than that of the control group when the PLBs were fed with 9 µM tryptophan, 6 µM secologanin and 100 µM MeJA after 36 days. HPLC analysis showed that strictosidine synthase (STR) activity also increased in the treated plants. A total of 78 metabolites were identified using gas chromatography-mass spectrometry (GC-MS) in combination with liquid chromatography-mass spectrometry (LC-MS) methods; 29 differential metabolites were identified according to the multivariate statistical analysis. Among them, carapanaubine, a kind of TIA, exhibited dramatically increased levels. In addition, a possible underlying process of the metabolic flux from related metabolism to the TIA biosynthetic pathway was enhanced. These results provide a comprehensive view of the metabolic changes related to alkaloid biosynthesis, especially TIA biosynthesis, in response to tryptophan, secologanin and MeJA treatment.