Orchids acquire fungal carbon for seed germination: pathways and players.

To germinate in nature, orchid seeds strictly rely on seed germination-promoting orchid mycorrhizal fungi (sgOMFs) for provision of carbon nutrients. The underlying delivery pathway, however, remains elusive. We develop here a plausible model for sugar transport from sgOMFs to orchid embryonic cells to fuel germination. Orchids exploit sgOMFs to induce the formation of pelotons, elaborate intracellular hyphal coils in orchid embryos. The colonized orchid cells then obtain carbon nutrients by uptake from living hyphae and peloton lysis, primarily as glucose derived from fungal trehalose hydrolyzed by orchid-specific trehalases. The uptake of massive fungally derived glucose is likely to be mediated by two classes of membrane proteins, namely, sugars will eventually be exported transporters (SWEETs) and H+-hexose symporters. The proposed model serves as a launch pad for further research to better understand and improve orchid seed germination and conservation.

Correction: Structural diversity, bioactivities, and biosynthesis of natural diterpenoid alkaloids.

Correction for 'Structural diversity, bioactivities, and biosynthesis of natural diterpenoid alkaloids' by Yong Shen et al., Nat. Prod. Rep., 2020, 37, 763-796, https://doi.org/10.1039/D0NP00002G.

Grafting: a potential method to reveal the differential accumulation mechanism of secondary metabolites.

Plant secondary metabolites make a great contribution to the agricultural and pharmaceutical industries. Their accumulation is determined by the integrated transport of target compounds and their biosynthesis-related RNA, protein, or DNA. However, it is hard to track the movement of these biomolecules in vivo. Grafting may be an ideal method to solve this problem. The differences in genetic and metabolic backgrounds between rootstock and scion, coupled with multiple omics approaches and other molecular tools, make it feasible to determine the movement of target compounds, RNAs, proteins, and DNAs. In this review, we will introduce methods of using the grafting technique, together with molecular biological tools, to reveal the differential accumulation mechanism of plant secondary metabolites at different levels. Details of the case of the transport of one diterpene alkaloid, fuziline, will be further illustrated to clarify how the specific accumulation model is shaped with the help of grafting and multiple molecular biological tools.

Metabolomics analysis of human plasma reveals decreased production of trimethylamine N-oxide retards the progression of chronic kidney disease.

BACKGROUND AND PURPOSE: Chronic kidney disease (CKD) is a global public health problem and one of the leading causes of all-cause mortality. However, the pathogenic mechanisms and intervention methods for CKD progression are not fully understood. EXPERIMENTAL APPROACH: Plasma from patients with uraemia and from healthy controls (n = 30 per group) was analysed with LC-MS/MS-based non-targeted metabolomics to identify potential markers of uraemia. These potential markers were validated in the same cohort and a second cohort (n = 195) by quantitative analysis of the markers, using LC-MS/MS. The most promising marker was identified by correlation analysis and further validated using HK-2 cells and mouse models. KEY RESULTS: Trimethylamine N-oxide (TMAO) was identified as a promising marker among the 18 potential markers found in the first cohort, and it was optimally correlated with renal function of CKD patients in the second cohort. Treatment of HK-2 cells with TMAO decreased cell viability and up-regulated expression of α-smooth muscle actin. In mice, a TMAO-containing diet decreased kidney mass and increased protein expression of α-smooth muscle actin. Also, control of TMAO production by inhibiting its biosynthetic pathway with 3,3-dimethyl-1-butanol or disrupting gut microbiota function with an antibiotic cocktail, attenuated renal injury in a murine model of CKD. CONCLUSION AND IMPLICATIONS: Our data show that decreased TMAO production could be a new strategy to attenuate the progression of renal injury in CKD.

Orchid Reintroduction Based on Seed Germination-Promoting Mycorrhizal Fungi Derived From Protocorms or Seedlings.

Orchids are among the most endangered in the plant kingdom. Lack of endosperm in their seeds renders orchids to depend on nutrients provided by orchid mycorrhizal fungi (OMF) for seed germination and seedling formation in the wild. OMF that parasitize in germination seeds is an essential element for orchid seedling formation, which can also help orchid reintroduction. Considering the limitations of the previous orchid reintroduction technology based on seed germination-promoting OMF (sgOMF) sourced from orchid roots, an innovative approach is proposed here in which orchid seeds are directly co-sown with sgOMF carrying ecological specificity from protocorms/seedlings. Based on this principle, an integrative and practical procedure concerning related ecological factors is further raised for re-constructing long-term and self-sustained orchid populations. We believe that this new approach will benefit the reintroduction of endangered orchids in nature.

Immunosuppressive Isopimarane Diterpenes From Cultures of the Endophytic Fungus Ilyonectria robusta.

Five new isopimarane diterpenes, robustaditerpene A-E (1-5), which include 19-nor-isopimarane skeleton and isopimarane skeleton, were isolated from the liquid fermentation of the endophytic fungus Ilyonectria robusta collected from Bletilla striata. The structure elucidation and relative configuration assignments of all compounds were accomplished by interpretation of NMR and HRESIMS spectrometric analyses and 13C NMR calculation. And the absolute configuration of 1-5 were identified by single-crystal X-ray diffraction and ECD calculation. Compound 3 inhibited lipopolysaccharide-induced B lymphocytes cell proliferation with an IC50 value at 17.42 ± 1.57 µM while compound 5 inhibited concanavalin A-induced T lymphocytes cell proliferation with an IC50 value at 75.22 ± 6.10 µM. These data suggested that compounds 3 and 5 may possess potential immunosuppressive prospect.

Solanum steroidal glycoalkaloids: structural diversity, biological activities, and biosynthesis.

Covering: up to 1 October 2020Solanum steroidal glycoalkaloids (SGA), characterized by nitrogenous steroidal aglycone and glycoside residues, mainly occur in the Solanum species, including economically important edible plants such as potato, tomato, and eggplant. To date, 107 SGA assigned to six total skeletons have been identified from Solanum plants. SGA have unique structures and display significant pharmacological activities such as cytotoxic, antimicrobial, anticholesterol, and some are well-known poisons. The biosynthesis pathway, transcriptional regulation, and the evolution of SGA are also examined in detail. This report updates the chemical knowledge of the naturally occurring SGA from Solanum species, thereby providing an in-depth analysis of their diversity, biological activities, and biosynthesis.

Conosiligins A-D, Ring-Rearranged Tremulane Sesquiterpenoids from Conocybe siliginea.

Conosiligins A-D (1-4), four ring-rearranged sesquiterpenoids, were isolated from cultures of the basidiomycete Conocybe siliginea. Their structures and absolute configurations were determined by detailed spectroscopic analyses and equivalent circulating density (ECD) calculations. Compounds 1 and 2 possess a 5/8-fused ring system, while 3 has a 5/6-fused backbone conjugated with a γ-lactone. Compound 4 is a 5,6-seco tremulane derivative with the loss of a skeletal carbon, featuring a tetracyclic system involving a pyranone moiety. Compounds 3 and 4 inhibited Con A-induced T cell proliferation with IC50 values of 12.3 and 6.6 µM, respectively.

Fungi isolated from host protocorms accelerate symbiotic seed germination in an endangered orchid species (Dendrobium chrysotoxum) from southern China.

To ensure long-term survival of epiphytic orchids through active reintroduction, more research on critical life cycle stages such as seed germination and seedling establishment are needed. In this study, we used in vitro germination experiments to investigate the role of mycorrhizal fungi in determining seed germination and growth in the endangered epiphytic orchid species, Dendrobium chrysotoxum. Symbiotic seed germination experiments were conducted for 90 days under different light conditions with fungal strains isolated from protocorms of D. chrysotoxum and three sister species. Molecular analyses showed that five strains belonged to the typical orchid mycorrhizal family Tulasnellaceae, whereas the other two strains belonged to the Sebacinaceae and the genus Coprinellus. Fungal inoculation, light conditions, and their interaction had a significant effect on protocorm formation and seedling development. Three fungal isolates, including two from D. chrysotoxum and one from D. catenatum, significantly stimulated protocorm formation and seedling development under light conditions. However, fungi isolated from host protocorms (GC-14 and GC-15) produced the highest number of seedlings after 50 days (49.5 ± 8.5%, 51.3 ± 9.0%, respectively), while the fungus isolated from D. catenatum protocorms produced the maximum number of seedlings only after 90 days (48.7 ± 16.1%). To conclude, this study has shown that light conditions and the identity of fungi had a strong effect on in vitro seed germination and seedling formation in an epiphytic orchid, with fungi isolated from host protocorms leading to accelerated germination and seedling formation. Therefore, fungal source should be taken into account when using seeds and compatible fungi for seedling propagation and in situ reintroduction.

Structural diversity, bioactivities, and biosynthesis of natural diterpenoid alkaloids.

Covering: 2009 to 2018. Diterpenoid alkaloids, originating from the amination of natural tetracyclic diterpenes, are a diverse class of compounds having complex structural features with many stereocenters. The important pharmacological activities and structural complexity of the diterpenoid alkaloids have long interested scientists due to their medicinal uses, infamous toxicity, and unique biosynthesis. Since 2009, 373 diterpenoid alkaloids, assigned to 46 skeletons, have been isolated and identified from plants mostly in the Ranunculaceae family. The names, classes, molecular weight, molecular formula, NMR data, and plant sources of these diterpene alkaloids are collated here. This review will be a detailed update of the naturally occurring diterpene alkaloids reported from the plant kingdom from 2009-2018, providing an in-depth discussion of their diversity, biological activities, pharmacokinetics, toxicity, application, evolution, and biosynthesis.

Overexpression of the Melatonin Synthesis-Related Gene SlCOMT1 Improves the Resistance of Tomato to Salt Stress.

Melatonin can increase plant resistance to stress, and exogenous melatonin has been reported to promote stress resistance in plants. In this study, a melatonin biosynthesis-related SlCOMT1 gene was cloned from tomato (Solanum lycopersicum Mill. cv. Ailsa Craig), which is highly expressed in fruits compared with other organs. The protein was found to locate in the cytoplasm. Melatonin content in SlCOMT1 overexpression transgenic tomato plants was significantly higher than that in wild-type plants. Under 800 mM NaCl stress, the transcript level of SlCOMT1 in tomato leaf was positively related to the melatonin contents. Furthermore, compared with that in wild-type plants, levels of superoxide and hydrogen peroxide were lower while the content of proline was higher in SlCOMT1 transgenic tomatoes. Therefore, SlCOMT1 was closely associated with melatonin biosynthesis confers the significant salt tolerance, providing a clue to cope with the growing global problem of salination in agricultural production.

Inhibition of soluble epoxide hydrolase attenuates a high-fat diet-mediated renal injury by activating PAX2 and AMPK.

A high-fat diet (HFD) causes obesity-associated morbidities involved in macroautophagy and chaperone-mediated autophagy (CMA). AMPK, the mediator of macroautophage, has been reported to be inactivated in HFD-caused renal injury. However, PAX2, the mediator for CMA, has not been reported in HFD-caused renal injury. Here we report that HFD-caused renal injury involved the inactivation of Pax2 and Ampk, and the activation of soluble epoxide hydrolase (sEH), in a murine model. Specifically, mice fed on an HFD for 2, 4, and 8 wk showed time-dependent renal injury, the significant decrease in renal Pax2 and Ampk at both mRNA and protein levels, and a significant increase in renal sEH at mRNA, protein, and molecular levels. Also, administration of an sEH inhibitor, 1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl)urea, significantly attenuated the HFD-caused renal injury, decreased renal sEH consistently at mRNA and protein levels, modified the renal levels of sEH-mediated epoxyeicosatrienoic acids (EETs) and dihydroxyeicosatrienoic acids (DHETs) as expected, and increased renal Pax2 and Ampk at mRNA and/or protein levels. Furthermore, palmitic acid (PA) treatment caused significant increase in Mcp-1, and decrease in both Pax2 and Ampk in murine renal mesangial cells (mRMCs) time- and dose-dependently. Also, 14(15)-EET (a major substrate of sEH), but not its sEH-mediated metabolite 14,15-DHET, significantly reversed PA-induced increase in Mcp-1, and PA-induced decrease in Pax2 and Ampk. In addition, plasmid construction revealed that Pax2 may positively regulate Ampk transcriptionally in mRMCs. This study provides insights into and therapeutic target for the HFD-mediated renal injury.

Jaboticabin and Related Polyphenols from Jaboticaba ( Myrciaria cauliflora) with Anti-inflammatory Activity for Chronic Obstructive Pulmonary Disease.

Myrciaria cauliflora (jaboticaba) is an edible fruit common in Brazil that has been used for treating respiratory diseases, including chronic tonsillitis and asthma. This study explores the distribution of an anti-inflammatory depside, jaboticabin, in different parts of the jaboticaba plant as well as major polyphenols from the wood of jaboticaba, some with biological activity similar to jaboticabin. The peel of the fruit was found to be the major source of jaboticabin. This is the first phytochemical study of the wood of M. cauliflora. The antioxidant-activity-guided fractionation strategy successfully identified 3,3'-dimethylellagic acid-4- O-sulfate from jaboticaba wood. This ellagic acid derivative, in a manner similar to jaboticabin, showed antiradical activity and inhibited the production of the chemokine interleukin-8 after treating the human small airway epithelial cells with cigarette smoke extract. The human intestinal Caco-2 cell studies demonstrated the jaboticabin transport in vitro. The polyphenols, jaboticabin and 3,3'-dimethyellagic acid-4- O-sulfate, from jaboticaba were both found to exhibit anti-inflammatory activities, thus suggesting the potential use of these compounds or even the fruits themselves for chronic obstructive pulmonary disease.

Four new C19-diterpenoid alkaloids from the roots of Aconitum ouvrardianum.

Four new C19-diterpenoid alkaloids, 3-dehydroxyl-lipoindaconitine (1), 8-dehydroxyl-bikhaconine (2), 19R-acetonyl-talatisamine (3), and 16-hydroxyl-vilmorisine (4), were isolated from the roots of Aconitum ouvrardianum. Their structures were elucidated by spectral analyses, including ESI-MS, HR-ESI-MS, IR, UV, 1D and 2D NMR.

Two new bis-C20-diterpenoid alkaloids with anti-inflammation activity from Aconitum bulleyanum.

Two new bis-C20-diterpenoid alkaloids, bulleyanines A and B (1 and 2), were isolated from Aconitum bulleyanum. Their structures were elucidated by comprehensive spectroscopic analyses including UV, IR, MS, 1D and 2D NMR. Biological activity tests indicated that compound 1 exhibited significant inhibitory activity against nitric oxide (NO) production in lipopolysaccharide (LPS)-activated RAW264.7 macrophages with the inhibition rate of 74.60% (40 µmol/L), while positive control dexamethasone gave 78.70% inhibition at 100 µg/ml.

Two new C19-diterpenoid alkaloids from Aconitum tsaii.

Two new C19-diterpenoid alkaloids, 14-benzoylliljestrandisine (1) and 14-anisoylliljestrandisine (2), were isolated from the roots of Aconitum tsaii. Their structures were elucidated by different spectroscopic (IR, UV, 1D and 2D NMR) and mass-spectrometric techniques.

Two new C19-diterpenoid alkaloids from Aconitum straminiflorum.

Two new C19-diterpenoid alkaloids, straconitines A (1) and B (2), were isolated from the roots of Aconitum straminiflorum. Their structures were elucidated as 14-benzoylducloudine D (1) and 6-hydroxy-14-benzoylducloudine D (2) based on spectroscopic analysis, including IR, ESI-MS, HR-ESI-MS, 1D, and 2D NMR.

Identification of glutathione S-transferase (GST) genes from a dark septate endophytic fungus (Exophiala pisciphila) and their expression patterns under varied metals stress.

Glutathione S-transferases (GSTs) compose a family of multifunctional enzymes that play important roles in the detoxification of xenobiotics and the oxidative stress response. In the present study, twenty four GST genes from the transcriptome of a metal-tolerant dark septate endophyte (DSE), Exophiala pisciphila, were identified based on sequence homology, and their responses to various heavy metal exposures were also analyzed. Phylogenetic analysis showed that the 24 GST genes from E. pisciphila (EpGSTs) were divided into eight distinct classes, including seven cytosolic classes and one mitochondrial metaxin 1-like class. Moreover, the variable expression patterns of these EpGSTs were observed under different heavy metal stresses at their effective concentrations for inhibiting growth by 50% (EC50). Lead (Pb) exposure caused the up-regulation of all EpGSTs, while cadmium (Cd), copper (Cu) and zinc (Zn) treatments led to the significant up-regulation of most of the EpGSTs (p < 0.05 to p < 0.001). Furthermore, although heavy metal-specific differences in performance were observed under various heavy metals in Escherichia coli BL21 (DE3) transformed with EpGSTN-31, the over-expression of this gene was able to enhance the heavy metal tolerance of the host cells. These results indicate that E. Pisciphila harbored a diverse of GST genes and the up-regulated EpGSTs are closely related to the heavy metal tolerance of E. pisciphila. The study represents the first investigation of the GST family in E. pisciphila and provides a primary interpretation of heavy metal detoxification for E. pisciphila.

Four new C18-diterpenoid alkaloids with analgesic activity from Aconitum weixiense.

Four new C18-diterpenoid alkaloids, weisaconitines A-D (1-4), were isolated from Aconitum weixiense. Based on extensive UV, IR, MS, 1D and 2D NMR analyses, their structures were elucidated as 8-O-ethyldolaconine (1), 4-demethylgenicunine B (2), 14-oxoaconosine (3), and 8-O-ethylaconosine (4). The analgesic activity of compound 4 was studied with CH3COOH-induced writhing model in mice. Compound 4 showed writhing inhibitions of 24% (50 mg/kg), 26% (100 mg/kg) and 34% (200 mg/kg), respectively, as compared to the reference drug aspirin (63%) at a dose of 200 mg/kg.

Two new compounds from an endophytic fungus Alternaria solani.

Two new secondary metabolites, named 7-dehydroxyl-zinniol (1) and 20-hydroxyl-ergosta-4,6,8(14),22-tetraen-3-one (2), were isolated from the culture of Alternaria solani, an endophytic fungal strain residing in the roots of Aconitum transsectum. Their structures were elucidated on the basis of comprehensive spectroscopic analyses including IR, ESI-MS, HR-ESI-MS, 1D and 2D NMR. Biological activity tests indicated that compound 1 showed moderate anti-HBV activity.