Identification of Nematicidal Constituents of Notopterygium incisum Rhizomes against Bursaphelenchus xylophilus and Meloidogyne incognita

Current Status and Prospects of Pine Wilt Disease Management with Phytochemicals-A Review

PWD (pine wilt disease) is a devastating forest disease caused by the Bursaphelenchus xylophilus, which is the major invasive species in Asian and European countries. To control this disease, fumigation, pesticide injection, and clear cutting of epidemic trees have been widely used. But these management strategies have many limitations in terms of the effectiveness and environmental impacts, especially for the overuse of chemical pesticides. Thus, PCs (phytochemicals), the various compounds extracted from plants, have drawn extensive attention owing to their special characteristics, including abundant sources, low toxicity, high efficacy, and easy degradation. This review provides an overview of the current status of using PCs as alternative approaches to manage PWD. It discusses the efficacy of various PCs, the factors influencing their nematicidal activity, and their mechanism of action against B. xylophilus. These results will reveal the application of PCs in combating these devastating diseases and the necessity for further research.

Two Undescribed Coumarins from Notopterygium Incisum with Anti-Inflammatory Activity

Two previously undescribed coumarins (1-2) were isolated from the root of Notopterygium incisum. The structures of new findings were elucidated by analyses of spectral evidences in HRESIMS, NMR, as well as ICD. The absolute configurations were further confirmed by chemical calculations. 1-2 exhibits obviously anti-inflammatory activity by inhibiting the expression of inflammatory mediators (COX-2, iNOS), as well as reducing the release of NO and the accumulation of ROS in cells. Western blotting analysis revealed that 2 could inhibit the PI3K/AKT pathway by reducing the expression of p-PI3K and p-AKT.

Phytochemistry and Biological Profile of the Chinese Endemic Herb Genus Notopterygium

Notopterygium, a plant genus belonging to the Apiaceae family, is utilized in traditional Chinese medicine for its medicinal properties. Specifically, the roots and rhizomes of these plants are employed in phytotherapy to alleviate inflammatory conditions and headaches. This review provides a concise overview of the existing information regarding the botanical description, phytochemistry, pharmacology, and molecular mechanisms of the two Notopterygium species: Notopterygium incisum and N. franchetii. More than 500 distinct compounds have been derived from these plants, with the root being the primary source. These components include volatile oils, coumarins, enynes, sesquiterpenes, organic acids and esters, flavonoids, and various other compounds. Research suggests that Notopterygium incisum and N. franchetii exhibit a diverse array of pharmacological effects, encompassing antipyretic, analgesic, anti-inflammatory, antiarrhythmic, anticoagulant, antibacterial, antioxidant, and anticancer properties on various organs such as the brain, heart, digestive system, and respiratory system. Building activity screening models based on the pharmacological effects of Notopterygium species, as well as discovering and studying the pharmacological mechanisms of novel active ingredients, will constitute the primary development focus of Notopterygium medicinal research in the future.

Exogenous and Endophytic Fungal Communities of Dendrobium nobile Lindl. across Different Habitats and Their Enhancement of Host Plants' Dendrobine Content and Biomass Accumulation

Both the biosynthesis and array of bioactive and medicinal compounds in plants can be influenced by interactions with endophytic and exogenous fungi. However, the composition of endophytic and exogenous fungal communities associated with many medicinal plants is unknown, and the mechanism by which these fungi stimulate the secondary metabolism of host plants is unclear. In this study, we conducted a correlative analysis between endophytic and exogenous fungi and dendrobine and biomass accumulation in Dendrobium nobile across five Chinese habitats: wild Danxia rock, greenhouse-associated large Danxia stone, broken Danxia stone, broken coarse sandstone, and wood spile. Across habitats, fungal communities exhibited significant differences. The abundances of Phyllosticta, Trichoderma, and Hydropus were higher in wild habitats than in greenhouse habitats. Wild habitats were host to a higher diversity and richness of exogenous fungi than were greenhouse habitats. However, there was no significant difference in endophytic fungal diversity between habitats. The differences between the fungal communities' effects on the dendrobine content and biomass of D. nobile were attributable to the composition of endophytic and exogenous fungi. Exogenous fungi had a greater impact than endophytic fungi on the accumulation of fresh weight (FW) and dendrobine in D. nobile. Furthermore, D. nobile samples with higher exogenous fungal richness and diversity exhibited higher dendrobine content and FW. Phyllosticta was the only genus to be significantly positively correlated with both FW and dendrobine content. A total of 86 strains of endophytic fungi were isolated from the roots, stems, and leaves of D. nobile, of which 8 strains were found to be symbiotic with D. nobile tissue-cultured seedlings. The strain DN14 (Phyllosticta fallopiae) was found to promote not only biomass accumulation (11.44%) but also dendrobine content (33.80%) in D. nobile tissue-cultured seedlings. The results of this study will aid in the development of strategies to increase the production of dendrobine in D. nobile. This work could also facilitate the screening of beneficial endophytic and exogenous fungal probiotics for use as biofertilizers in D. nobile.

Natural nematicidal metabolites and advances in their biocontrol capacity on plant parasitic nematodes

Covering: 2010 to 2021Natural nematicidal metabolites are important sources of nematode control. This review covers the isolation and structural determination of nematicidal metabolites from 2010 to 2021. We summarise chemical structures, bioactivity, metabolic regulation and biosynthesis of potential nematocides, and structure-activity relationship and application potentiality of natural metabolites in plant parasitic nematodes' biocontrol. In doing so, we aim to provide a comprehensive overview of the potential roles that natural metabolites can play in anti-nematode strategies.

GC-MS Analysis of the Essential Oil from Seseli mairei H. Wolff (Apiaceae) Roots and Their Nematicidal Activity

The essential oil (EO) was extracted from aerial parts with insecticidal and fungicidal activity. Herein, the hydro-distilled essential oils of Seseli mairei H. Wolff roots were determined by GC-MS. A total of 37 components were identified, (E)-beta-caryophyllene (10.49%), β-geranylgeranyl (6.64%), (E)-2-decenal (6.17%) and germacrene-D (4.28%). The essential oil of Seseli mairei H. Wolff had nematicidal toxicity against Bursaphelenchus xylophilus with a LC₅₀ value of 53.45 μg/mL. The subsequent bioassay-guided investigation led to the isolation of three active constituents: falcarinol, (E)-2-decenal, and octanoic acid. The falcarinol demonstrated the strongest toxicity against B. Xylophilus (LC₅₀ = 8.52 μg/mL). The octanoic acid and (E)-2-decenal also exhibited moderate toxicity against B. xylophilus (LC₅₀ = 65.56 and 176.34 μg/mL, respectively). The LC₅₀ of falcarinol for the toxicity of B. xylophilus was 7.7 and 21 times than that of octanoic acid and (E)-2-decenal, respectively. Our findings demonstrate that the essential oil from Seseli mairei H. Wolff roots and their isolates may be developed as a promising natural nematicide.

Nematicidal Activities of Saccharin and Erythritol Against Pinewood Nematode

The pinewood nematode (PWN), Bursaphelenchus xylophilus (Steiner & Bührer), causes pine wilt disease (PWD) resulting in severe environmental damage to pine forest ecosystems worldwide. To develop alternative strategies for managing PWD, the nematicidal activities of two sweeteners, erythritol and saccharin, were investigated. Among these two sweeteners, saccharin induced higher mortality in a dose-dependent manner. The LC₅₀ and LC₉₀ values of saccharin were estimated to be 0.321 M and 0.615 M, respectively. However, erythritol did not exhibit nematicidal activities. The results of our study demonstrated that saccharin is lethal to PWN and shows nematicidal effects in a dose-dependent manner. Although the mechanisms of saccharin toxicity are not yet investigated, saccharin could be used as an effective alternative for the management of PWN.

One-Pot Synthesis of Benzopyrano-Pyrimidine Derivatives Catalyzed by P-Toluene Sulphonic Acid and Their Nematicidal and Molecular Docking Study

A cost-effective and environmentally benign benzopyrano-pyrimidine derivative synthesis has been established with the condensation of different salicylaldehyde derivatives, piperidine/morpholine with malononitrile, in the presence of a catalyst containing p-toluene sulphonic acid (PTSA) at 80 °C temperature. This procedure offers a new and enriched approach for synthesizing benzopyrano-pyrimidine derivatives with high yields, a straightforward experimental method, and short reaction times. The synthesized compounds were investigated for their nematocidal activity, and the result shows that among the four compounds, compounds 4 and 5 showed strong nematocidal activity against egg hatching and J2s mortality. The nematocidal efficacy of the compounds might be due to the toxicity of chemicals which are soluble in ethanol. The nematocidal effectiveness was directly related to the concentration of ethanolic dilutions of the compounds, i.e., the maximum treatment concentration, the higher the nematocidal action, or the higher the mortality and egg hatching inhibition. In the present study, with support from docking analysis, the relation between chemical reactivity and nematocidal activity of compound 4 was inferred.

Gene sdaB Is Involved in the Nematocidal Activity of Enterobacter ludwigii AA4 Against the Pine Wood Nematode Bursaphelenchus xylophilus

Bursaphelenchus xylophilus, a plant parasitic nematode, is the causal agent of pine wilt, a devastating forest tree disease. Essentially, no efficient methods for controlling B. xylophilus and pine wilt disease have yet been developed. Enterobacter ludwigii AA4, isolated from the root of maize, has powerful nematocidal activity against B. xylophilus in a new in vitro dye exclusion test. The corrected mortality of the B. xylophilus treated by E. ludwigii AA4 or its cell extract reached 98.3 and 98.6%, respectively. Morphological changes in B. xylophilus treated with a cell extract from strain AA4 suggested that the death of B. xylophilus might be caused by an increased number of vacuoles in non-apoptotic cell death and the damage to tissues of the nematodes. In a greenhouse test, the disease index of the seedlings of Scots pine (Pinus sylvestris) treated with the cells of strain AA4 plus B. xylophilus or those treated by AA4 cell extract plus B. xylophilus was 38.2 and 30.3, respectively, was significantly lower than 92.5 in the control plants treated with distilled water and B. xylophilus. We created a sdaB gene knockout in strain AA4 by deleting the gene that was putatively encoding the beta-subunit of L-serine dehydratase through Red homologous recombination. The nematocidal and disease-suppressing activities of the knockout strain were remarkably impaired. Finally, we revealed a robust colonization of P. sylvestris seedling needles by E. ludwigii AA4, which is supposed to contribute to the disease-controlling efficacy of strain AA4. Therefore, E. ludwigii AA4 has significant potential to serve as an agent for the biological control of pine wilt disease caused by B. xylophilus.

A Review of the Potency of Plant Extracts and Compounds from Key Families as an Alternative to Synthetic Nematicides: History, Efficacy, and Current Developments

The global nematicides market is expected to continue growing. With an increasing demand for synthetic chemical-free organic foods, botanical nematicides are taking the lead as replacements. Consequently, in the recent years, there have been vigorous efforts towards identification of the active secondary metabolites from various plants. These include mostly glucosinolates and their hydrolysis products such as isothiocyanates; flavonoids, alkaloids, limonoids, quassinoids, saponins, and the more recently probed essential oils, among others. And despite their overwhelming potential, variabilities in quality, efficacy, potency and composition continue to persist, and commercialization of new botanical nematicides is still lagging. Herein, we have reviewed the history of botanical nematicides and regional progresses, the potency of the identified phytochemicals from the key important plant families, and deciphered some of the impediments involved in standardization of the active compounds in addition to the concerns over the safety of the purified compounds to non-target microbial communities.

An Active Compound From Pseudomonas aeruginosa B27

A compound was isolated from the fermented broth of Pseudomonas aeruginosa. The compound was determined as acridine-4-carboxylic acid based on nuclear magnetic resonance, mass spectrometry (MS), and single-crystal x-ray diffraction analysis. Acridine-4-carboxylic acid showed significant antibacterial activities against Staphylococcus aureus, Bacillus cereus, Bacillus subtilis, Bacillus megaterium, and Shinella sp. Moreover, the compound showed certain antitumor activities against HCT116, ST486, HCC1806, and A549 with IC50values of 38.38, 6.59, 20.69, and 82.81 μg/mL, respectively. In the test of nematicidal activity, acridine-4-carboxylic acid showed certain nematicidal activity against Caenorhabditis elegans and Meloidogyne incognita. In addition, the compound also exhibited 1,1-diphenyl-2-picrylhydrazyl free radical scavenging activity. Therefore, this compound may be used as a potential antibacterial, antitumor, nematicidal, and antioxidative agent.

Contents of lobetyolin, syringin, and atractylolide III in Codonopsis pilosula are related to dynamic changes of endophytes under drought stress

Background

Codonopsis pilosula, an important medicinal plant, can accumulate certain metabolites under moderate drought stress. Endophytes are involved in the metabolite accumulations within medicinal plants. It is still unknown that the endophytes of C. pilosula are associated with the accumulations of metabolites. This study aims to investigate the promoting effect of endophytes on the accumulations of active substances in C. pilosula under drought stress.

Methods

High–performance liquid chromatography and high–throughput sequencing technology were performed to investigate changes in the contents of secondary metabolite and endophyte abundances of C. pilosula under drought stress, respectively. Spearman’s correlation analysis was further conducted to identify the endophytic biomarkers related to accumulations of pharmacodynamic compounds. Culture-dependent experiments were performed to confirm the functions of endophytes in metabolite accumulations.

Results

The distribution of pharmacological components and diversity and composition of endophytes showed tissue specificity within C. pilosula. The contents of lobetyolin, syringin, and atractylolide III in C. pilosula under drought stress were increased by 8.47%‒86.47%, 28.78%‒230.98%, and 32.17%‒177.86%, respectively, in comparison with those in untreated groups. The Chao 1 and Shannon indices in different parts of drought–stressed C. pilosula increased compared with those in untreated parts. The composition of endophytic communities in drought treatment parts of C. pilosula was different from that in control parts. A total of 226 microbial taxa were identified as potential biomarkers, of which the abundances of 42 taxa were significantly and positively correlated to the pharmacodynamic contents. Culture-dependent experiments confirmed that the contents of lobetyolin and atractylolide III were increased by the application of Epicoccum thailandicum, Filobasidium magnum, and Paraphoma rhaphiolepidis at the rates of 11.12%‒46.02%, and that the content of syringin was increased by Pseudomonas nitroreducens at the rates of 118.61%‒119.36%.

Conclusions

Certain endophytes participated in the accumulations of bioactive metabolites, which provided a scientific evidence for the development and application of microorganisms to improve the quality of traditional Chinese medicine.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13020-021-00533-z.

α-Linolenic acid in Papilio machaon larvae regurgitant induces a defensive response in Apiaceae

Papilio machaon hippocrates C. Felder et R. Felder, 1864 (Papilionidae) larvae are pests of plants of the family Apiaceae. It is unclear whether Apiaceae plants show induced defensive responses against P. machaon hippocrates larvae, and if so, how these responses are induced. Comparison of the fatty acid (FA) composition of the leaves of host plants and the regurgitant of P. machaon hippocrates larvae by LC-MS revealed a great increase in α-linolenic acid (α-LA) in the regurgitant compared with the FAs contained in the leaves. However, specific FA amino acid conjugates, known as elicitor compounds, such as volicitin, were not detected. Sterile host plants (Saposhnikovia divaricata (Turcz.) Schischk., Apiaceae) were treated with α-LA to mimic the damage made by P. machaon hippocrates larvae. After α-LA treatment to leaves, induced defensive reactions, i.e., release of volatile compounds such as α- and β-pinene and camphene (possible induced indirect defense) and the accumulation of specialized metabolites such as (R)-falcarinol and bergapten (possible induced direct defense) were observed. These findings highlight the role of α-LA in the interaction between P. machaon hippocrates larvae and Apiaceae host plants.

The potential of Apiaceae species as sources of singular phytochemicals and plant-based pesticides

The Apiaceae Lindl. (=Umbelliferae Juss.), which includes several economical important vegetables, herbs, and spices, is one of the most numerous plant family. Umbelliferous crops (namely anise, fennel, carrot, coriander, parsley, etc.) are also valuable sources of botanical flavoring agents and fragrances. In addition, Apiaceae species yield a wide variety of distinctive specialized metabolites (i.e, volatile phenylpropanoids, furanocoumarins, sesquiterpene coumarins, polyacetylenes, and phthalides), some of them been described as uncommon natural phytochemicals exclusive of the family, which offers a great potential for bioprospection. Numerous studies have pointed out the outstanding biological activity of extracts and several classes of phytochemicals from Apiaceae species. Emphasis has been given to essential oils (EOs) and their constituents activities, most likely because this type of plant added value product benefits from a larger acceptance and application potential in integrated pest management (IPM) and integrated vector management (IVM) programs. Several species of the family offer a variety of unique compounds with great potential as biopesticidal and/or synergizing agents. Investigations covering their activity toward agricultural pests and phytopathogens have increased in the last years, nevertheless the interest remains strongly focus on arthropod species, predominantly those acting as vectors of human diseases. From our survey, it is patent the gap of knowledge concerning the potential molluscicidal properties of Apiaceae extracts/phytochemicals, as well as their herbicidal activities against invasive plant species. In this review, we propose to highlight the potential of Apiaceae species as suitable sources of bioactive phytochemicals with great relevance within the frame of plant-based pesticides R&D, and will discuss their applicability in real-world scenarios considering the recent developments regarding the design of stable formulations incorporating Apiaceae bioactive products. We expect that this review will encourage researchers to consider undervalued Apiaceae species as alternative sources of bioactive compounds and will give a contribute to the field by suggesting new research topics.

Essential Oils from Two Apiaceae Species as Potential Agents in Organic Crops Protection

Chemical composition and herbicidal, antifungal, antibacterial and molluscicidal activities of essential oils from Choukzerk, Eryngium triquetrum, and Alexander, Smyrnium olusatrum, from western Algeria were characterized. Capillary GC-FID and GC/MS were used to investigate chemical composition of both essential oils, and the antifungal, antibacterial, molluscicidal and herbicidal activities were determined by % inhibition. Collective essential oil of E. triquetrum was dominated by falcarinol (74.8%) and octane (5.6%). The collective essential oil of S. olusatrum was dominated by furanoeremophilone (31.5%), furanodiene+curzurene (19.3%) and (E)-β-caryophyllene (11%). The E. triquetrum oil was tested and a pure falcarinol (99%) showed virtuous herbicidal and antibacterial activities against potato blackleg disease, Pectobacterium atrosepticum, and Gram-negative soil bacterium, Pseudomonas cichorii (85 and 100% inhibition, respectively), and high ecotoxic activity against brine shrimp, Artemia salina, and the freshwater snail, Biomphalaria glabrata, with an IC₅₀ of 0.35 µg/mL and 0.61 µg/mL, respectively. Essential oil of S. olusatrum showed interesting antibacterial and ecotoxic activity and good herbicidal activity against watercress seeds, Lepidium sativum (74% inhibition of photosynthesis, 80% mortality on growth test on model watercress), while the furanoeremophilone isolated from the oil (99% pure) showed moderate herbicidal activity. Both oils showed excellent antifungal activity against Fusarium. Both oils and especially falcarinol demonstrated good potential as new biocontrol agents in organic crop protection.

Transcriptomic Analysis of Resistant and Susceptible Responses in a New Model Root-Knot Nematode Infection System Using Solanum torvum and Meloidogyne arenaria

Root-knot nematodes (RKNs) are among the most devastating pests in agriculture. Solanum torvum Sw. (Turkey berry) has been used as a rootstock for eggplant (aubergine) cultivation because of its resistance to RKNs, including Meloidogyne incognita and M. arenaria. We previously found that a pathotype of M. arenaria, A2-J, is able to infect and propagate in S. torvum. In vitro infection assays showed that S. torvum induced the accumulation of brown pigments during avirulent pathotype A2-O infection, but not during virulent A2-J infection. This experimental system is advantageous because resistant and susceptible responses can be distinguished within a few days, and because a single plant genome can yield information about both resistant and susceptible responses. Comparative RNA-sequencing analysis of S. torvum inoculated with A2-J and A2-O at early stages of infection was used to parse the specific resistance and susceptible responses. Infection with A2-J did not induce statistically significant changes in gene expression within one day post-inoculation (DPI), but afterward, A2-J specifically induced the expression of chalcone synthase, spermidine synthase, and genes related to cell wall modification and transmembrane transport. Infection with A2-O rapidly induced the expression of genes encoding class III peroxidases, sesquiterpene synthases, and fatty acid desaturases at 1 DPI, followed by genes involved in defense, hormone signaling, and the biosynthesis of lignin at 3 DPI. Both isolates induced the expression of suberin biosynthetic genes, which may be triggered by wounding during nematode infection. Histochemical analysis revealed that A2-O, but not A2-J, induced lignin accumulation at the root tip, suggesting that physical reinforcement of cell walls with lignin is an important defense response against nematodes. The S. torvum-RKN system can provide a molecular basis for understanding plant-nematode interactions.

Rapid and intelligent discrimination of Notopterygium incisum and Notopterygium franchetii by infrared spectroscopic fingerprints and electronic olfactory fingerprints

This preliminary research evaluated mid-infrared (MIR) spectroscopy, near-infrared (NIR) spectroscopy and electronic nose (E-nose) for the rapid identification of Notopterygium incisum and Notopterygium franchetii, which were both approved sources of Notopterygii Rhizoma et Radix (Chinese Pharmacopoeia, 2015) but possessed different chemical compositions and pharmacological activities. At the level of single variables, MIR showed quite a few discriminating peaks in the regions of 3000-2800 cm^-1 (the stretching bands of CH), 1770-1670 cm^-1 (the stretching bands of CO), and 1400-1200 cm^-1 (the bending bands of CH and the stretching bands of CO). Meanwhile, NIR only showed an intuitive discriminating peak near 4736 cm^-1 (the combination band of OH and CO stretching modes). E-nose response signals of N. incisum and N. franchetii were significant different (p < 0.05) on four sensors, i.e., LY2/LG, LY2/GH, LY2/gCT and LY2/gCTI. Using the infrared spectra or E-nose sensor responses as fingerprints, support vector machine (SVM) models can provide good recognition accuracy (100% for MIR and NIR models, 92.9% for E-nose model). This research indicated the feasibility of MIR, NIR and E-nose for the accurate, rapid, cheap and green identification of N. incisum and N. franchetii, which was desirable to assure the authenticity, efficacy and safety of related herb materials and products.

Phylogenetic characterization of bacterial endophytes from four Pinus species and their nematicidal activity against the pine wood nematode

Recently, bacterial endophytes (BEs) have gained importance in the agricultural sector for their use as biocontrol agents to manage plant pathogens. Outbreak of the pine wilt disease (PWD) in Korea has led researchers to test the feasibility of BEs in controlling the pine wood nematode (PWN) Bursaphelenchus xylophilus. In this study, we have reported the diversity and biocontrol activity of BEs against the PWN. By employing a culture-dependent approach, 1,622 BEs were isolated from the needle, stem, and root tissues of P. densiflora, P. rigida, P. thunbergii, and P. koraiensis across 18 sampling sites in Korea. We classified 389 members based on 16S rDNA analysis and taxonomic binning, of which, 215 operational taxonomic units (OTUs) were determined. Using Shannon’s indices, diversity across the Pinus species and tissues was estimated to reveal the composition of BEs and their tissue-specific preferences. When their ethyl acetate crude extracts were analysed for biocontrol activity, 44 candidates with nematicidal activity were obtained. Among these, Stenotrophomonas and Bacillus sp. exhibited significant inhibitory activity against PWN during their developmental stages. Altogether, our study furnishes a basic comprehension of bacterial communities found in the Pinus species and highlights the potential of BEs as biocontrol agents to combat PWD.

Distribution and diversity of bacterial endophytes from four Pinus species and their efficacy as biocontrol agents for devastating pine wood nematodes

In this study, we isolated a total of 238 culturable putative bacterial endophytes from four Pinus species (Pinus densiflora, P. koraiensis, P. rigida, and P. thunbergii) across 18 sampling sites in Korea. The samples were cultured in de Man Rogosa Sharpe and humic acid-vitamin agar media. These selective media were used to isolate lactic acid bacteria and Actinobacteria, respectively. Analysis using 16S ribosomal DNA sequencing grouped the isolated putative bacterial endophytes into 107 operational taxonomic units (OTUs) belonging to 48 genera. Gamma-proteobacteria were the most abundant bacteria in each sampling site and three tissues (needle, stem and root). The highest OTU richness and diversity indices were observed in the roots, followed by stem and needle tissues. Total metabolites extracted from three isolates (two isolates of Escherichia coli and Serratia marcescens) showed significant nematicidal activity against the pine wood nematode (Bursaphelenchus xylophilus). Our findings demonstrated the potential use of bacterial endophytes from pine trees as alternative biocontrol agents against pine wood nematodes.

Notopterygium incisum extract and associated secondary metabolites inhibit apple fruit fungal pathogens

In the search for antifungal lead compounds from natural resources, Notopterygium incisum, a medicine plant only distributed in China, showed antifungal potential against apple fruit pathogens. Based on the bioassay-guided isolation, chromatography fraction 6 of the ethyl acetate partition exhibited significant in vitro and in vivo antifungal activities against apple fruit pathogens. Furthermore, nine antifungal secondary metabolites, including five linear furocoumarins (1-5), two phenylethyl esters (6-7), one falcarindiol (8), and one sesquiterpenoid (9), were isolated and elucidated from fraction 6. Compound 5 is a new metabolite, and 9 isolated from the genus Notopterygium for the first time. The purified compounds (1-9) were firstly reported to exhibit antifungal activities against apple fruit pathogens of Colletotrichum gloeosporioides and Botryosphaeria dothidea with the MIC values ranging from 8 to 250 mg L^-1, especially 8 of 16 and 8 mg L^-1, respectively. Moreover, 8 could inhibit the spore germination and new sporulation of B. dothidea, as well as enhance the membrane permeabilization of B. dothidea spores. This was the first investigation for the antifungal components against apple fruit pathogens from Notopterygium incisum, which has great potential to be developed into bio-fungicides.

Suppressing a plant-parasitic nematode with fungivorous behavior by fungal transformation of a Bt cry gene

BACKGROUND

Pine wilt disease, caused by the pinewood nematode Bursaphelenchus xylophilus (PWN), is an important destructive disease of pine forests worldwide. In addition to behaving as a plant-parasitic nematode that feeds on epithelial cells of pines, this pest relies on fungal associates for completing its life cycle inside pine trees. Manipulating microbial symbionts to block pest transmission has exhibited an exciting prospect in recent years; however, transforming the fungal mutualists to toxin delivery agents for suppressing PWN growth has received little attention.

RESULTS

In the present study, a nematicidal gene cry5Ba3, originally from a soil Bacillus thuringiensis (Bt) strain, was codon-preferred as cry5Ba3Φ and integrated into the genome of a fungus eaten by PWN, Botrytis cinerea, using Agrobacterium tumefaciens-mediated transformation. Supplementing wild-type B. cinerea extract with that from the cry5Ba3Φ transformant significantly suppressed PWN growth; moreover, the nematodes lost fitness significantly when feeding on the mycelia of the cry5Ba3Φ transformant. N-terminal deletion of Cry5Ba3Φ protein weakened the nematicidal activity more dramatically than did the C-terminal deletion, indicating that domain I (endotoxin-N) plays a more important role in its nematicidal function than domain III (endotoxin-C), which is similar to certain insecticidal Cry proteins.

CONCLUSIONS

Transformation of Bt nematicidal cry genes in fungi can alter the fungivorous performance of B. xylophilus and reduce nematode fitness. This finding provides a new prospect of developing strategies for breaking the life cycle of this pest in pines and controlling pine wilt disease.

Endophytic bacteria: a new source of bioactive compounds

In recent years, bioactive compounds are in high demand in the pharmaceuticals and naturopathy, due to their health benefits to human and plants. Microorganisms synthesize these compounds and some enzymes either alone or in association with plants. Microbes residing inside the plant tissues, known as endophytes, also produce an array of these compounds. Endophytic actinomycetes act as a promising resource of biotechnologically valuable bioactive compounds and secondary metabolites. Endophytic Streptomyces sp. produced some novel antibiotics which are effective against multi-drug-resistant bacteria Antimicrobial agents produced by endophytes are eco-friendly, toxic to pathogens and do not harm the human. Endophytic inoculation of the plants modulates the synthesis of bioactive compounds with high pharmaceutical properties besides promoting growth of the plants. Hydrolases, the extracellular enzymes, produced by endophytic bacteria, help the plants to establish systemic resistance against pathogens invasion. Phytohormones produced by endophytes play an essential role in plant development and drought resistance management. The high diversity of endophytes and their adaptation to various environmental stresses seem to be an untapped source of new secondary metabolites. The present review summarizes the role of endophytic bacteria in synthesis and modulation of bioactive compounds.