Changes in Diversity and Composition of Rhizosphere Bacterial and Fungal Community between Resistant and Susceptible Pakchoi under .

() is a soil-born pathogen worldwide and can infect most cruciferous plants, which causes great yield decline and economic losses. It is not well known how microbial diversity and community composition change during infecting plant roots. Here, we employed a resistant and a susceptible pakchoi cultivar with and without inoculation with to analyze bacterial and fungal diversity using 16S rRNA V3-V4 and ITS_V1 regions, respectively.

Human-associated bacteria adopt an unusual route for synthesizing 3-acetylated tetramates for environmental adaptation.

Background: Tetramates or tetramic acid-containing compounds (TACs) are a group of bioactive natural products featuring a pyrrolidine-2,4-dione ring acknowledged being closed via Dieckmann cyclization. The cariogenic Streptococcus mutans strains bearing a muc biosynthetic gene cluster (BGC) can synthesize mutanocyclin (MUC), a 3-acetylated TAC that can inhibit both leukocyte chemotaxis and filamentous development in Candida albicans. Some strains can also accumulate reutericyclins (RTCs), the intermediates of MUC biosynthesis with antibacterial activities.

-Quinone Methide-Mediated Nonenzymatic Formation of Chalcane-Containing Dimers in Dragon's Blood.

Chalcane-containing dimers are major compounds identified from dragon's blood, the red resin that accumulates in trees after injury. The key step for the formation of these dimers was a -quinone methide (-QM, ) mediated nonenzymatic Michael addition. Compound is derived from the spontaneous dehydration of chalcane alcohol-M274 ().

Precursor Supply Increases the Accumulation of 4-Hydroxy-6-(4-hydroxyphenyl)-α-pyrone after NRPS-PKS Gene Expression.

Expression of a nonribosomal peptide synthetase-nonreducing polyketide synthase hybrid gene from PRB-2 in led to the accumulation of 4-hydroxy-6-(4-hydroxyphenyl)-α-pyrone (). Adding -hydroxybenzoic acid into the medium in which the overexpressing mutant is growing increased the product yield up to 5-fold. This strategy could be helpful for heterologous gene expression experiments requiring special substrates for product formation.

Increasing Structural Diversity of Natural Products by Michael Addition with -Quinone Methide as the Acceptor.

The active form of clavatol, -quinone methide, can be generated from hydroxyclavatol in an aqueous system and used as a highly reactive intermediate for coupling with diverse natural products under very mild conditions. These include flavonoids, hydroxynaphthalenes, coumarins, xanthones, anthraquinones, phloroglucinols, phenolic acids, indole derivatives, tyrosine analogues, and quinolines. The clavatol moiety was mainly attached via C-C bonds to the - or -positions of phenolic hydroxyl/amino groups and the C2-position of the indole ring.

Formation of Terrestric Acid in Requires Redox-Assisted Decarboxylation and Stereoisomerization.

Crustosic acid () differs from terrestric acid () by a 5β-carboxylmethyl at the tetronate ring instead of a 5α-methyl group in . The formation of via carboxylcrustic and viridicatic acid was confirmed by gene deletion and heterologous expression. The conversion of to requires a decarboxylation-mediated olefination by TraH and subsequent reduction by TraD.

Five new epoxy-5,6,7,8-tetrahydro-2-(2-phenylethyl)chromones from Chinese agarwood by artificial holing.

Five optically active epoxy-5,6,7,8-tetrahydro-2-(2-phenylethyl)chromone derivatives (1-5) with four chirality centers in the condensed cyclohexene ring were isolated from artificial holing agarwood originating from Aquilaria sinensis (Lour.) Gilg. Their structures were elucidated by spectroscopic techniques (UV, IR, 1D and 2D NMR) and MS analyses.

Peniphenone and Penilactone Formation in Penicillium crustosum via 1,4-Michael Additions of ortho-Quinone Methide from Hydroxyclavatol to γ-Butyrolactones from Crustosic Acid.

Penilactones A and B consist of a γ-butyrolactone and two clavatol moieties. We identified two separate gene clusters for the biosynthesis of these key building blocks in Penicillium crustosum. Gene deletion, feeding experiments, and biochemical investigations proved that a nonreducing PKS ClaF is responsible for the formation of clavatol and the PKS-NRPS hybrid TraA is involved in the formation of crustosic acid, which undergoes decarboxylation and isomerization to the predominant terrestric acid.

Complete Decoration of the Indolyl Residue in cyclo-l-Trp-l-Trp with Geranyl Moieties by Using Engineered Dimethylallyl Transferases.

Mutation of the gatekeeping residues for prenyl donor selectivity in six dimethylallyl transferases significantly increased their activities toward geranyl diphosphate. Forty-two geranylated derivatives were obtained from 15 cyclic dipeptides by using the engineered enzymes. Taking cyclo-l-Trp-l-Trp as an example, the geranyl moiety can be attached to all seven possible positions of the indole nucleus.

Monitoring the Chemical Profile in Agarwood Formation within One Year and Speculating on the Biosynthesis of 2-(2-Phenylethyl)Chromones.

Agarwood is highly valued for its uses as incense, perfume, and medicine. However, systematic analyses of dynamic changes of secondary metabolites during the process of agarwood formation have not yet been reported. In this study, agarwood was produced by transfusing the agarwood inducer into the trunk of , and changing patterns of chemical constituents, especially 2-(2-phenylethyl)chromones (PECs), in wood samples collected from the 1st to 12th month, were analyzed by GC-EI-MS and UPLC-ESI-MS/MS methods.

New Eudesmane-Type Sesquiterpenoids from the Mangrove-Derived Endophytic Fungus Penicillium sp. J-54.

Four new eudesmane-type sesquiterpenoids, penicieudesmol A-D (-), were isolated from the fermentation broth of the mangrove-derived endophytic fungus sp. J-54. Their structures were determined by spectroscopic methods, the in situ dimolybdenum CD method, and modified Mosher's method.

Four new bi-phenylethylchromones from artificial agarwood.

Four new bi-phenylethylchromones (1-4) were isolated from the EtOAc extract of artificial agarwood induced by holing method originating from Aquilaria sinensis (Lour.) Gilg. The structures of new compounds were unambiguously elucidated by one- and two-dimensional NMR and HRESIMS measurements, and the absolute configuration was determined by analysis of circular dichroism (CD) spectra.

5,6,7,8-Tetrahydro-2-(2-phenylethyl)chromones from artificial agarwood of Aquilaria sinensis and their inhibitory activity against acetylcholinesterase.

Thirteen previously undescribed 5,6,7,8-tetrahydro-2-(2-phenylethyl)chromones named tetrahydrochromone A-M, together with nine known ones, were isolated from artificial agarwood (induced by holing) originating from Aquilaria sinensis (Lour.) Gilg. The structures of these compounds were unambiguously determined based on extensive NMR spectroscopic analyses, and the absolute configuration was resolved by CD analyses, X-ray crystallographic, chemical and Mosher's method.

Characterization and Analysis of 2-(2-Phenylethyl)-chromone Derivatives from Agarwood (Aquilaria crassna) by Artificial Holing for Different Times.

A total of fifty-six chromones, including seven 5,6,7,8-tetrahydro-2-(2-phenylethyl)-chromones (THPECs), five 5,6-epoxy-2-(2-phenylethyl)chromones (EPECs), seven 5,6:7,8-diepoxy-2-(2-phenylethyl)chromones (DEPECs) and thirty-seven 2-(2-phenylethyl)chromones of the flidersia type (FTPECs), were characterized by HPLC/DAD/ESI/MS/MS in three agarwood samples (from Aquilaria crassna) induced by artificial holing with different holing times. The characteristic fragmentation behavior of DEPECs and EPECs, and the methods to distinguish these four types of chromones by MS analysis were described for the first time. In addition, it was found that the relative contents of DEPECs and EPECs were down-regulated, while the relative contents of THPECs and FTPECs were up-regulated for the samples from two, four and five years of the agarwood formation time.

Sesquiterpenoids from Chinese Agarwood Induced by Artificial Holing.

Two new sesquiterpenoids, 3-oxo-7-hydroxylholosericin A (1) and 1,5;8,12-diepoxy-guaia-12-one (2), together with seven known sesquiterpenoids 3-9, were isolated from Chinese agarwood induced by artificial holing originating from Aquilaria sinensis (Lour.) Gilg. Their structures were identified by spectroscopic techniques (UV, IR, 1D and 2D NMR) and MS analyses.

2-(2-Phenylethyl)chromone derivatives in artificial agarwood from Aquilaria sinensis.

Seven new 2-(2-phenylethyl)chromone derivatives (1-7) including a chlorinated one (4), together with eight known ones (8-15), were isolated from the EtOAc extract of artificial agarwood originating from Aquilaria sinensis (Lour.) Gilg. All structures including the absolute configurations were unambiguously elucidated by spectroscopic (NMR, UV, IR, MS) methods, Mosher's method, and comparison with reported data in the literatures.