Onygenaleosides A-F, 6/5 Bicyclic Ring Skeleton Triterpene Glycosides with Insecticidal Activity from Onygenales sp. YX1425.

Six new squalene derived polyether glycosides, onygenaleosides A-F (1-6), that possess a 6/5 bicyclic fused ring skeleton were isolated from the cultures of Onygenales sp. YX1425, along with two known analogues (7 and 8). The planar structures of the new compounds were elucidated based on analysis of NMR and MS spectroscopy data, and the absolute configuration of 1 was determined by the advanced Mosher method and quantum chemical calculations. Compound 2 was active against Spodoptera frugiperda with an LC50 value of 193.4 ± 1.1 µg/mL.

Mass Spectrometry-Guided Discovery of Multi-N-Methylated Cyclodecapeptides Auyuittuqamides E-H from Sesquicillium sp. QL0466.

Mass spectrometry-based dereplication and prioritization led to the discovery of four multi-N-methylated cyclodecapeptides, auyuittuqamides E-H (1-4), from a soil-derived Sesquicillium sp. The planar structures of these compounds were elucidated based on analysis of HRESIMS and NMR data. Absolute configurations of the chiral amino acid residues were assigned by a combination of the advanced Marfey's method, chiral-phase LC-MS analysis, and J-based configuration analysis, revealing that 1-4 contain both d- and l-isomers of N-methylleucine (MeLeu). Differentiation of d- and l-MeLeu in the sequence was achieved by advanced Marfey's analysis of the diagnostic peptide fragments generated from partial hydrolysis of 1. Bioinformatic analysis identified a putative biosynthetic gene cluster (auy) for auyuittuqamides E-H, and a plausible biosynthetic pathway was proposed. These newly identified fungal cyclodecapeptides (1-4) displayed in vitro growth inhibitory activity against vancomycin-resistant Enterococcus faecium with MIC values of 8 µg/mL.

Characterization of Bacterial Communities Associated with Rhynchophorus ferrugineus Olivier (Coleoptera: Curculionidae) and its Host Phoenix sylvestris.

This study measured the changes of microorganisms in the midgut and habitat niche of Rhynchophorus ferrugineus Olivier, an invasive quarantine pest, by Illumina sequencing. The bacterial diversity in the R. ferrugineus larvae midgut and their habitat niche was compared to the uninfected P. sylvestris. The Proteobacteria and Firmicutes occupied a dominant position in the R. ferrugineus midgut and infected P. sylvestris, while in the uninfected P. sylvestris the predominant bacterial phylum was the Cyanobacteria. Enterobacter, Dysgonomonas, and Entomoplasma were the dominant bacterial genera in R. ferrugineus midgut and also within the infected trees and uninfected trees with low relative abundance. These bacteria could be exploited as the biopesticide vector to control R. ferrugineus population. Besides, Sphingobacterium, Shinella, and Rhodobacter genera had the same distribution pattern in the infected and uninfected P. sylvestris, and these bacteria were not found in the midgut of R. ferrugineus. Interestingly, Paludibacter and Parabacteroides were only distributed in the wood fiber of the infected P. sylvestris, which could be used as potential microbial markers to detect if the palm plants are damaged by the R. ferrugineus. The results of this study will be beneficial to the development of control strategies for R. ferrugineus.

Isolation, Characterization, and Bioherbicidal Potential of the 16-Residue Peptaibols from Emericellopsis sp. XJ1056.

Eco-friendly bioherbicides are urgently needed for managing the problematic weed Amaranthus retroflexus. A mass spectrometry- and bioassay-guided screening approach was employed to identify phytotoxic secondary metabolites from fungi for the development of such bioherbicides. This effort led to the discovery of six phytotoxic 16-residue peptaibols, including five new compounds (2-6) and a known congener (1), from Emericellopsis sp. XJ1056. Their planar structures were elucidated through the analysis of tandem mass and NMR spectroscopic data. The absolute configurations of the chiral amino acids were determined by advanced Marfey's method and chiral-phase liquid chromatography-mass spectrometry (LC-MS) analysis. Bioinformatic analysis and targeted gene disruption identified the biosynthetic gene cluster for these peptaibols. Compounds 1 and 2 significantly inhibited the radicle growth of A. retroflexus seedlings, and 1 demonstrated potent postemergence herbicidal activity against A. retroflexus while exhibiting minimal toxicity to Sorghum bicolor. Structure-activity relationship analysis underscored the importance of trans-4-hydroxy-l-prolines at both the 10th and 13th positions for the herbicidal activities of these peptaibols.

Proteolytic Activation of Bacillus thuringiensis Cry3Aa Toxin in the Red Palm Weevil (Coleoptera: Curculionidae).

The red palm weevil (RPW), Rhynchophorus ferrugineus (Oliver) is an important pest of palms that causes significant damage by boring into and feeding within palm stem tissues. Here, we studied the proteolytic process of Cry3Aa in the RPW to understand the mechanism of Cry toxicity. The bioassays showed that Cry3Aa toxin is weakly toxic to the RPW. Proteolytic activation assays indicated the Cry3Aa protein is digested into smaller fragments than the 55-kDa activated fragments under different conditions. In particular, at higher mass ratios of gut protease and Cry3Aa protein (5:1, 2:1, and 1:1, respectively), and at 36.9°C for 16 h in a solution of pH 8.6, the Cry3Aa protoxin is over-digested by the gut proteases of weevil larvae. Moreover, the zymogram analysis of the gut proteases revealed the RPW larvae harbors intestinal digestive enzymes mainly composed of serine proteases. This study describes the proteolytic activation process of Cry3Aa in the midgut of RPW larvae.