The alcohol dehydrogenase with a broad range of substrate specificity regulates vitality and reproduction of the plant-parasitic nematode Bursaphelenchus xylophilus

Transcriptome Study of Bursaphelenchus xylophilus Treated with Fomepizole Reveals a Serine/Threonine-Protein Phosphatase Gene that Is Substantially Linked with Vitality and Pathogenicity

Bursaphelenchus xylophilus, the pine wood nematode (PWN), is the causal agent of pine wilt disease (PWD), which causes enormous economic loss annually. According to our previous research, fomepizole, as a selective inhibitor of PWN alcohol dehydrogenase (ADH), has the potential to be a preferable lead compound for developing novel nematicides. However, the underlying molecular mechanism is still unclear. The result of molecular docking showed that the stronger interactions between fomepizole and PWN ADH at the active site of ADH were attributed to hydrogen bonds. Low-dose fomepizole had a substantial negative impact on the egg hatchability, development, oviposition, and lifespan of PWN. Transcriptome analysis indicated that 2,124 upregulated genes and 490 downregulated genes in fomepizole-treated PWN were obtained. Kyoto Encyclopedia of Genes and Genomes enrichment analysis of differentially expressed genes indicated that fomepizole could be involved in controlling PWN vitality mainly by regulating key signaling pathways, such as the ribosome, hippo signaling pathway, and lysosome. Remarkably, the results of RNA interference indicated that the downregulated serine/threonine-protein phosphatase gene (stpp) could reduce the egg hatchability, development, oviposition, and lifespan of PWN, which was closely similar to the consequences of nematodes with low-dose fomepizole treatment. In addition, the silencing of stpp resulted in weakness of PWN pathogenicity, which indicated that stpp could be a potential drug target to control PWN.

Effect of Associated Bacteria GD1 on the Low-Temperature Adaptability of Bursaphelenchus xylophilus Based on RNA-Seq and RNAi

To explore the effect of associated bacteria on the low-temperature adaptability of pinewood nematodes (PWNs), transcriptome sequencing (RNA-seq) of PWN AH23 treated with the associated bacterial strain Bacillus cereus GD1 was carried out with reference to the whole PWN genome. Bioinformatic software was utilized to analyze the differentially expressed genes (DEGs). This study was based on the analysis of DEGs to verify the function of daf-11 by RNAi. The results showed that there were 439 DEGs between AH23 treated with GD1 and those treated with ddH₂O at 10 °C. There were 207 pathways annotated in the KEGG database and 48 terms annotated in the GO database. It was found that after RNAi of daf-11, the survival rate of PWNs decreased significantly at 10 °C, and fecundity decreased significantly at 15 °C. It can be concluded that the associated bacteria GD1 can enhance the expression of genes related to PWN low-temperature adaptation and improve their adaptability to low temperatures.

Novel Lead Compound Discovery from Aspergillus fumigatus 1T-2 against Meloidogyne incognita Based on a Chemical Ecology Study

To replace biohazardous nematicides, there is an ever-increasing need to identify natural product-based agents to contain root-knot nematodes (RKNs) in agriculture. In this chemical ecology study, an antagonistic fungus Aspergillus fumigatus 1T-2, which could cause the formation of withering of the gut and vacuole-like structures in the nematode body, was isolated based on the gradually increased antagonistic interactions between the soil fungi and RKNs. Based on these typical morphological characteristics, a potent nematode-antagonistic compound 2-furoic acid, which had a simple structure, was successfully identified from 1T-2 fermentation broth by liquid chromatography-mass spectrometry (LC-MS). 2-Furoic acid showed effective mortality activity in vitro, of which the LC₅₀ value to Megalaima incognita at 24 h was 37.75 μg/mL. 2-Furoic acid had similar mortality activity to the positive control fosthiazate at 30 μg/mL. Continuous 2-furoic acid exposure had obvious negative influences on both nematode vitality and egg hatchability. Notably, significant variations were observed in nematodes and eggs with 2-furoic acid treatment, which might be induced by novel nematocidal mechanisms. Furthermore, the 1T-2 fermentation broth and 2-furoic acid had significant control efficacy on M. incognita under the greenhouse test-tube assay. Overall, these findings provide valuable insights into the use of 2-furoic acid with biocontrol potential as a preferable lead structure for the development of innovative nematicides.

Transcriptomics and coexpression network profiling of the effects of levamisole hydrochloride on Bursaphelenchus xylophilus

Bursaphelenchus xylophilus is one of the most dangerous forest pathogens in the world, causing devastating pine forest deaths with considerable economic losses. In this study, we investigated the B. xylophilus RNA sequence responses of two different concentrations of levamisole hydrochloride (LH). We observed that body-wall muscle twitching, paralysis and, ultimately, death. 2.5 mg/ml and 3.5 mg/ml LH have toxicological effects on B. xylophilus, with mortality increasing significantly with concentration (p < 0.05). RNA sequencing, differential gene expression analysis, and cluster analysis were performed, and 336, 384, 6 genes with significant variance in expression were identified. Gene Ontology annotation and Kyoto Encyclopedia of Genes and Genomes pathway analyses of the 12 intersecting genes revealed that these genes are mostly involved in metabolism of xenobiotics and have essential roles in drug sensitivity. Through the trend analysis of DEGs, it was divided into 8 modules, and the significant modules were selected to construct the co-expression network as the central genes of the drug metabolism-cytochrome P450 pathway (ko00982) and metabolism of xenobiotics by cytochrome P450 (ko00980). Eight highly related genes were identified, including cuticle collagen, cystathionine beta-synthase, endochitinase, pyruvate dehydrogenase E1 component subunit beta, aldehyde dehydrogenase, lipase, and zinc metalloproteinase. The expression levels of these genes were upregulated significantly at low concentrations and were significantly related to the resistance of B. xylophilus to LH. This study shows that B. xylophilus gene family expansions occurred in xenobiotic detoxification pathways through gene expression and potential horizontal correlated gene transfer with LH and helps to elucidate LH lethality and the evolutionary mechanisms underlying the adaptations of B. xylophilus to the environment. These results contributing to our understanding of B. xylophilus under LH and provide a data platform to providing a basis for its control.

Research Progress on Oviposition-Related Genes in Insects

Oviposition-related genes have remained a consistent focus of insect molecular biology. Previous research has gradually clarified our mechanistic understanding of oviposition-related genes, including those related to oviposition-gland-related genes, oogenesis-related genes, oviposition-site-selection-related genes, and genes related to ovulation and hatching. Moreover, some of this research has revealed how the expression of single oviposition-related genes affects the expression of related genes, and more importantly, how individual node genes function to link the expression of upstream and downstream genes. However, the research to date is not sufficient to completely explain the overall interactions among the genes of the insect oviposition system. Through a literature review of a large number of studies, this review provides references for future research on oviposition-related genes in insects and the use of RNAi or CRISPR/Cas9 technology to verify the functions of oviposition-related genes and to prevent and control harmful insects.