Metabolomic and regular analysis reveal phytotoxic mechanisms of sterigmatocystin in Amaranthus retroflexus L.

Sterigmatocystin (STE) is a common hepatotoxic and nephrotoxic contaminant in cereals, however, its phytotoxicity and mechanisms are poorly understood. Here, the phytotoxic mechanisms of STE were investigated via the metabolomics of Amaranthus retroflexus L. A total of 140 and 113 differential metabolites were detected in the leaves and stems, respectively, among which amino acids, lipids, and phenolic compounds were significantly perturbed. Valine, leucine, isoleucine, and lysine biosynthesis were affected by STE. These metabolic responses revealed that STE might be toxic to plants by altering the plasma membrane and inducing oxidative damage, which was verified by measuring the relative electrical conductivity and quantification of reactive oxygen species. The elevated amino acids, as well as the decreased of D-sedoheptuiose-7-phosphate indicated increased proteolysis and carbohydrate metabolism restriction. Furthermore, the IAA level also decreased. This study provides a better understanding of the impacts of STE on the public health, environment and food security.

Decalintetracids A and B, two pairs of unusual 3-decalinoyltetramic acid derivatives with phytotoxicity from Fusarium equiseti D39.

The filamentous fungi Fusarium sp. are well-known for their ability to produce abundant specialised metabolites with attractive chemical structures and bioactivities. In this study, chemical analyses of the endophyte F. equiseti D39 led to the isolation and identification of two pairs of undescribed 3-decalinoyltetramic acids (3DTAs) E/Z diastereomers, decalintetracids A and B. Their structures were elucidated by comprehensive spectroscopic analysis and quantum-chemical calculations. Although 3DTAs were commonly reported from fungi, decalintetracid A possessed an unprecedented tricyclo [7.2.1.02,7] dodecane skeleton, which added the diversity of these fungal metabolites. In addition, decalintetracid B was featured by a unique 6/6/5 ring system core. A plausible biosynthetic pathway for decalintetracids A and B was proposed. Both compounds exhibited phytotoxicity toward Amaranthus retroflexus L. and Amaranthus hybrid, indicating their potential as natural herbicides.

Herbicidal and Antifungal Xanthone Derivatives from the Alga-Derived Fungus Aspergillus versicolor D5.

Fungi have been proved as promising and prolific sources of functional secondary metabolites with potent agricultural applications. In this study, 14 xanthone derivatives (1-14), including six new ones, versicones I-N (1-4, 7, 11), and a biogenetically related derivative (15), were isolated from the alga-derived fungus Aspergillus versicolor D5. Their structures were elucidated by comprehensive spectroscopic methods. Versicone L (4) exhibited a broad antifungal spectrum and prominent inhibitory effects on Botrytis cinerea at a minimum inhibitory concentration (MIC) of 152 µM, 7-fold stronger than that of the positive control, carbendazim (MIC = 1.05 × 103 µM). Dihydrosterigmatocystin (13) showed strong antifungal activity toward B. cinerea at MIC = 38.3 µM, almost 30-fold stronger than that of carbendazim. Meanwhile, 13 exhibited potent herbicidal activity toward Amaranthus retroflexus L. with an MIC of 24.5 µM, approximately 4-fold stronger than that of the positive control, glyphosate (MIC = 94.7 µM). Additionally, 13 also displayed remarkable activity against other weeds belonging to Amaranth sp. Analysis of the structure-herbicidal activity relationship indicated that the bifuranic ring played an important role in xanthone phytotoxicity and the presence of a double bond in the furan ring could decrease phytotoxicity. This study indicated that xanthones can be served as promising candidates for lead compounds of agrochemicals.

Essential oil of Chrysanthemum indicum L.: potential biocontrol agent against plant pathogen Phytophthora nicotianae.

Phytophthora nicotianae is currently considered one of the most devastating oomycete plant pathogens, and its control frequently relies solely on the use of systemic fungicides. There is an urgent need to find environment-friendly control techniques. This study examined the chemical composition, inhibitory activity, and possible modes of action of the essential oil of Chrysanthemum indicum L. (EOC) flower heads against P. nicotianae. The EOC was obtained using hydrodistillation at a 0.15% yielded. It inhibited mycelial growth and spore germination of P. nicotianae at a minimum inhibitory concentration (MIC) of 200 µL/L, and exhibited fumigation effects (92.68% inhibition at 157.48 µL/L). Marked deformation of P. nicotianae mycelia included deformed tip enlargement, shrinkage, and rupture. Further, 55 and 47 compounds were identified using gas chromatography-mass spectrometry (GC-MS) and headspace solid-phase microextraction (HS-SPME) GC-MS analyses, representing 88.2% and 98.91% of the total EOC, respectively. Monoterpenes (25.77%) and sesquiterpenes (54.14%) were the major components identified using GC-MS, whereas monoterpenes were the main constituents in the HS-SPME GC-MS analysis. The higher proportions of sesquiterpenes and monoterpenes could be responsible for the inhibitory activity of EOC, which increased mycelia membrane permeability and the content of mycelial malondialdehyde (MDA) in a dose-dependent manner. Cell death also occurred. Thus, destruction of the cell wall and membrane might be two modes of action of EOC. Our results would be useful for the development of a new plant source of fungicide for P. nicotianae-induced disease.

Genetic analysis and identification of candidate genes for two spotted-leaf mutants (spl101 and spl102) in rice.

Spotted-leaf mutants form spots in leaves or leaf sheaths under normal condition. The spotted-leaf phenotypes are similar to hypersensitive reaction of plants attacked by pathogen. Identification and characterization of the spotted-leaf mutants are helpful for understanding the mechanisms of resistance to plant diseases. Here, we identify two spotted-leaf mutants spl101 and spl102 from an EMS-treated elite japonica cultivar KYJ (Kuanyejing). spl101 and spl102 form serious spots at the late heading stage. Genetic analyses show that the spotted-leaf phenotypes of both spl101 and spl102 are caused by a single recessive mutation, respectively. By employing the Mutmap method, we reveal that both spl101 and spl102 contain mutations in the OsEDR1 gene. The spl101 mutation occurs in the 5°-splicing site of the 6th intron of OsEDR1, which causes abnormal recognition of the 6th intron and leads to the frameshift mutation. The spl102 mutant contains a mutation in the tenth exon of OsEDR1, resulting in an amino acid change from the phenylalanine (F) to the cysteine (C). OsEDR1 has been reported to regulate pathogen-resistant reaction, and loss of OsEDR1 function produces similar phenotypes to those of spl101 and spl102. Here, two newly identified alleles of OsEDR1 will be benefit for further understanding the molecular mechanisms of the OsEDR1 gene in disease resistance, and will be helpful for enriching the rice germplasm resources. In addition, our results also validate the effectiveness of the Mutmap method in cloning the candidate mutations.

Diode laser combined with intradiscal vancomycin for iatrogenic discitis: an experimental study in rabbits.

OBJECTIVE: The purpose of this study was to assess the efficacy of diode laser combined with intradiscal vancomycin for iatrogenic discitis (ID) infected with Staphylococcus aureus. BACKGROUND DATA: In vivo and in vitro studies have reported that diode laser has a potential bactericidal effect on S. aureus. METHODS: The rabbit ID model was induced by injecting S. aureus into the intervertebral discs (IVDs). The animals were classified into the following groups: Group M, model; Group N, non-treatment; Group O, operation; Group V, vancomycin; Group L, laser; and Group C, laser with vancomycin. The rabbits were killed when paraplegia occurred and target IVD regions were removed for histopathological examination. RESULTS: In Group M, MRI findings revealed narrowing of the disc space, with changed T1 and T2 signals. In Group N, pathological examination showed a narrowed disc space, inflammatory changes in disc tissue, extensive erosion and hyperostosis of bony end plates, and an epidural abscess. Narrowed disc space and bone fusion were observed in Group O. In Group V, narrowed disc spaces, focal inflammatory changes of the disc tissue, and focal erosion and hyperostosis of bony end plates were seen. In Groups L and C, cavitation, inflammatory lesions, focal erosion, and hyperostosis of bony endplates were observed. However, in Group C, fibrosis was found in the nucleus region, with a smaller area of cavitation and better preservation of IVD structure than in Group L. The ID score was lowest in Group O, at 9.7 ± 0.95. The ID scores in Groups V and L were 12.2 ± 1.32 and 12.6 ± 0.97, respectively, significantly less than in Group N. The Group C ID score of 10.9 ± 0.99 was significantly less than that of Groups N, V, and L. CONCLUSIONS: High power diode laser combined with intradiscal vancomycin contained the pathological process of ID in this rabbit model.