A Phytotoxin with Selective Herbicidal Activity and Related Metabolites from the Phytopathogenic Fungus Bipolaris cookei SYBL03.

Weeds are a serious threat to crop production, and the utilization of secondary metabolites of phytopathogenic fungi is considered to be an effective method of weed control. In this study, eight compounds were isolated and purified from the mycelium and fermentation broth extracts of Bipolaris cookei SYBL03. The compounds (1-8), except 2 and 6, are reported for the first time from this genus. The herbicidal activities of compounds 1-8 were studied by evaluating their effects on the seed germination and seedling growth of monocotyledonous and dicotyledonous weeds. The results indicated that compound 7 (Cyclo-N-methylphenylalanyltryptophenyl, cNMPT) exhibited a concentration-dependent dual effect on the growth of weed seedlings and selective herbicidal activity against dicotyledonous weeds. We further investigated the morphological and physiological responses of roots of Amaranthus retroflexus, a dicotyledonous weed, to compound 7. Some changes were found in seedlings grown in 400 µg/mL compound 7 solution for 96 h, such as shortening and swelling of elongation zone cells, reduced number and length of root hairs, damage and wrinkling of the root surface, occurrence of electrolyte leakage, and an increase in ethylene content. These results suggest that compound 7 may exert herbicidal activity by causing stress to weed seedlings. Increased ethylene production could be involved in the response of plants to compound 7.

Effects of Bipolaris yamadae strain HXDC-1-2 as a bioherbicide against Echinochloa crus-galli in rice and dry fields.

BACKGROUND: Barnyardgrass (Weed Science Society of America recommended) or Barnyard grass (Britannica recommended) (Echinochloa crus-galli (L.) P. Beauv.) is one of the most problematic and dominant weeds in world agricultural systems, especially in paddy fields, where tillering and grain yield can be reduced by 50-70% because of its competitive pressure. The frequent use of chemical herbicides to control E. crus-galli has led to the evolution of herbicide resistance. Developing bioherbicides using pathogenic fungi to control E. crus-galli could be an alternative option. RESULTS: In a previous study we showed that a strain of Bipolaris yamadae (HXDC-1-2) was promising in controlling gramineous weeds. Here we present a study that evaluated this fungus as a mycoherbicide against E. crus-galli in greenhouse and paddy fields, characterized mycelium growth and conidial production, and examined the infection development. The median effective dose (ED50) and 90% effective dose (ED90) values of microcapsulated B. yamadae strain HXDC-1-2 on E. crus-galli in the greenhouse were 7.17 × 102 and 9.35 × 103 conidia mL-1, respectively. Conidial germination, mycelial growth, and attachment formation occurred on E. crus-galli leaves within 1 to 6 h. The hyphae directly invaded cells and stomata, primarily from the appressorium on the epidermis, and necrotic lesions were observed on the leaf surface within 20 to 24 h. Applied to E. crus-galli plants at 1 × 105 conidia mL-1, the fungus reduced the weed's fresh weight of 75%. CONCLUSION: B. yamadae strain HXDC-1-2 has the potential to be developed as a bioherbicide against E. crus-galli plants, especially in rice fields. © 2024 Society of Chemical Industry.

Integrated omics approaches for deciphering antifungal metabolites produced by a novel Bacillus species, B. cabrialesii TE3T, against the spot blotch disease of wheat (Triticum turgidum L. subsp. durum).

Bipolaris sorokiniana is an important biotic constraint for global wheat production, causing spot blotch disease. In this work, we present a comprehensive characterization of the cell-free culture filtrate (CF) and precipitated fraction (PF) of Bacillus cabrialesii TE3T showing an effective inhibition of spot blotch. Our results indicated that CF produced by B. cabrialesii TE3T inhibits the growth of B. sorokiniana through stable metabolites (after autoclaving and proteinase K treatment). Antifungal metabolites in CF and PF were explored by an integrated genomic-metabolomic approach. Genome-mining revealed that strain TE3T contains the biosynthetic potential to produce wide spectrum antifungal (surfactin, fengycin, and rhizocticin A) and antibacterial metabolites (bacillaene, bacilysin, bacillibactin, and subtilosin A), and through bioactivity-guided LC-ESI-MS/MS approach we determined that a lipopeptide complex of surfactin and fengycin homologs was responsible for antifungal activity exhibited by B. cabrialesii TE3T against the studied phytopathogen. In addition, our results demonstrate that i) a lipopeptide complex inhibits B. sorokiniana by disrupting its cytoplasmatic membrane and ii) reduced spot blotch disease by 93 %. These findings show the potential application of metabolites produced by strain TE3T against B. sorokiniana and provide the first insight into antifungal metabolites produced by the novel Bacillus species, Bacillus cabrialesii.

Synthesis and Biological Activities of Novel (Z)-/(E)-Anisaldehyde-Based Oxime Ester Compounds.

In search of novel natural product-based bioactive molecules, twenty (ten pairs) novel (Z)-/(E)-anisaldehyde-based oxime ester compounds were designed and synthesized by using anisaldehyde as starting material. Structural characterization of the target compounds was carried out by NMR, FT-IR, ESI-MS, and elemental analysis. Their herbicidal and antifungal activities were preliminarily tested. As a result, at 50 µg/mL, compound (E)-5b exhibited excellent to good inhibition rates of 92.3 %, 79.2 %, and 73.9 %, against Rhizoctonia solani, Fusarium oxysporum f. sp. cucumerinum, and Bipolaris maydis, respectively, better than or comparable to that of the positive control chlorothalonil. In addition, at 100 µg/mL, compounds (E)-5b, (E)-5f, (Z)-5f and (E)-5d exhibited excellent to good inhibition rates of 85.8 %, 82.9 %, 78.6 % and 64.2 %, respectively, against the root-growth of rape (B. campestris), much better than that of the positive control flumioxazin. The bioassay result also showed that the synthesized compounds had obvious differences in antifungal and herbicidal activities between (Z)- and (E)-isomers. Preliminary structure-activity relationship was also discussed by theoretical calculation.

Antifungal Biphenyl Derivatives from Sorbus pohuashanensis Leaves Infected by Alternaria tenuissi and Their Effect against Crop Pathogens.

Eight natural biphenyl-type phytoalexins exhibiting antifungal effect were isolated from the leaves of Sorbus pohuashanensis, which invaded by Alternaria tenuissi, and their growth inhibition rate towards A. tenuissi were 50.3 %, 54.0 %, 66.4 %, 58.8 %, 48.5 %, 51.0 %, 33.3 %, and 37.0 %, respectively. In vivo activity assay verified the protective effect of these natural biphenyls on tobacco leaves. The observation of mycelial morphology revealed that these compounds possessed adverse effects on mycelial growth of A. tenuissi. Subsequently, the most potent active compounds, 3',4',5'-trimethoxy[1,1'-biphenyl]-4-ol (3) and 3,4,4',5-tetramethoxy-1,1'-biphenyl (4), were conducted to the further antifungal evaluation and showed significant activity against the other four crop pathogens, Fusarium graminearum, Helminthosporium maydis, Sclerotinia sclerotiorum, and Exserohilum turcicum. Further, the structure-activity relationships and biosynthesis of these compounds were speculated in this work.

Design, synthesis and inhibitory activity of novel 2, 3-dihydroquinolin-4(1H)-one derivatives as potential succinate dehydrogenase inhibitors.

Thirty-three new 2, 3-dihydroquinolin-4(1H)-one analogues were designed, synthesized and characterized by IR, 1H NMR, 13C NMR and HRMS. The crystal structures of compounds 2g and 4l were characterized by single crystal X-ray diffraction. Their antifungal activities were determined against five plant pathogenic fungi namely Rhizoctonia solani, Fusarum graminearum, Helminthosporium maydis, Sclerotinia sclerotiorum and Botrytis cinerea. The results indicated that most of them revealed significant antifungal activity at 20 mg/L. Compound 4e showed the strongest antifungal activity against Botrytis cinerea and had better effects than the commercial fungicide fluopyram. Meanwhile, the active compounds were evaluated for their inhibitory activities against succinate dehydrogenase (SDH). The results displayed that they exhibited excellent activity. Compound 4e had better inhibitory activity than fluopyram. The molecular modeling results demonstrated that compound 4e could strongly bind to and interact with the binding sites of SDH. The inhibitory activity of 2, 3-dihydroquinolin-4(1H)-one derivatives against SDH has been reported for the first time.

Titanium dioxide nanoparticles elicited agro-morphological and physicochemical modifications in wheat plants to control Bipolaris sorokiniana.

The current study involves the biogenesis of titanium dioxide nanoparticles (TiO2 NPs) by using Moringa oleifera Lam. aqueous leaf extract for the reduction of titanium dioxide salt into TiO2 nanoparticles. The biosynthesized TiO2 nanoparticles were observed by using the UV-visible spectrophotometry, SEM, EDX and XRD analytical methods. It was confirmed that the nanoparticles are crystalline and exist in the size range of 10-100 nm. The FTIR analysis confirmed the presence of O-H (hydrogen bonding), N-H (amide), C-C (alkanes) and C-I (Iodo-stretch) functional groups responsible for the stabilization of nanoparticles. Various concentrations (20, 40, 60 and 80 mg/L) of TiO2 NPs were applied exogenously on wheat plants infected with a fungus Bipolaris sorokiniana responsible to cause spot blotch disease at different time intervals. The measurement of disease incidence and percent disease index showed the time-dependent response and 40 mg/L was reported a stable concentration of TiO2 NPs to reduce the disease severity. The effects of biosynthesized TiO2 NPs were also evaluated for agro-morphological (leaf and root surface area, plant fresh and dry weight and yield parameters), physiological (relative water content, membrane stability index and chlorophyll content) and non-enzymatic metabolites (soluble sugar, protein, soluble phenol and flavonoid content) in wheat plants under biotic stress and 40 mg/L concentration of TiO2 NPs was found to be effective to elicit modifications to reduce biotic stress. The current study highlights the significant role of biosynthesized TiO2 NPs in controlling fungal diseases of wheat plants and thus ultimately improving the quality and yield of wheat plants.

Antifungal and Antimicroalgal Trichothecene Sesquiterpenes from the Marine Algicolous Fungus Trichoderma brevicompactum A-DL-9-2.

Eight new trichothecene derivatives, trichodermarins G-N (1-8), and two new cuparene derivatives, trichocuparins A (9) and B (10), as well as six known trichothecenes (11-16) were isolated from the fungal strain Trichoderma brevicompactum A-DL-9-2 obtained from the inner tissue of the marine red alga Chondria tenuissima. The structures and relative configurations of 1-10 were assigned by NMR and MS data, and the absolute configurations of 1, 2, and 9 were established by X-ray diffraction. Compound 8 features an aminosugar unit bond to the trichothecene framework for the first time, while 9 and 10 represent the first occurrence of cuparene sesquiterpenes in Trichoderma. All the isolates were assayed for growth inhibition of five phytopathogenic fungi (Botrytis cinerea, Cochliobolus miyabeanus, Fusarium oxysporum f. sp. cucumerium, Fusarium oxysporum f. sp. niveum, and Phomopsis asparagi) and four marine phytoplankton species (Amphidinium carterae, Heterocapsa circularisquama, Heterosigma akashiwo, and Prorocentrum donghaiense). Several of them exhibited significant inhibitory activities against the fungi and phytoplankton tested of which trichodermin (12) showed the highest antifungal and antimicroalgal activities with MIC and IC50 values being 4.0 and 0.82 µg/mL, respectively.

A novel mannose-binding lectin from Liparis nervosa with anti-fungal and anti-tumor activities.

Plant lectins are carbohydrate-binding proteins with nonimmune origin, which can reversibly bind with carbohydrates, agglutinate cells, and precipitate polysaccharides and glycoconjugates. Plant lectins have attracted much attention for their anti-virus, anti-proliferation, and pro-apoptosis properties. Thus the exploration of new lectins has received special attention. Here we purified a mannose-binding lectin from the rhizomes of Liparis nervosa by ion exchange chromatography on DEAE-Sepharose, affinity chromatography on Mannose-Sepharose 4B, and gel filtration chromatography on Sephacryl S-100. The purified L. nervosa lectin (LNL) was identified to be a monomeric protein with a molecular mass of 13 kDa. LNL exhibited hemagglutinating activity towards rabbit erythrocytes, and its activity could be strongly inhibited by D-mannose, N-acetyl glucosamine and thyroglobulin. In vitro experiments showed that LNL exhibited a comparable anti-fungal activity against Piricularia oryzae (Cavara), Bipolaris maydis, Fusarium graminearum, and Sclerotium rolfsii, and anti-proliferation activity against tumor cells by inducing apoptosis. The full-length cDNA sequence of LNL is 715 bp in length and contains a 525 bp open reading frame (ORF) encoding a 110-residue mature protein. It was predicted to have three mannose-binding conserved motifs 'QXDXNXVXY'. The binding pattern of LNL was further revealed by homology modeling and molecular docking. We demonstrated that LNL is not only a potential therapeutic candidate against tumor but also a new anti-fungal agent.