Eukaryotic Expression of the Cytochrome c Oxidase Subunit I of Sitophilus zeamais and Its Interaction with Allyl Isothiocyanate

Novel Insights into the Control of Sitophilus zeamais in Grain by Chitosan-Nanoparticle-Contained dsSzCOX

Sitophilus zeamais is a highly destructive pest of stored grains worldwide. To develop novel RNA insecticides, the double-stranded RNA of S. zeamais cytochrome c oxidase (dsSzCOXs: dsSzCOXI, dsSzCOXII, and dsSzCOXIII) was successfully expressed in the pET28a-BL21(DE3)-RNaseIII- system and remarkably downregulated the expression level of SzCOXs in S. zeamais through injection or feeding methods, leading to high mortalities in both larvae and adults. Under their optimal expression conditions (isopropyl β-d-thiogalactoside, 0.6 mM), the yields of dsSzCOXI (at 28 °C for 4 h), dsSzCOXII (at 37 °C for 6 h), and dsSzCOXIII (at 37 °C for 6 h) were 8.49, 5.80, and 6.04 μg/mL respectively. The chitosan-based gene delivery system composed of dsSzCOXs (CS@dsSzCOXs) was established for the insecticidal effect of S. zeamais adults via mixing wheat seeds, with the mortality reaching 50% on day ten. Consequently, this nanoparticle-mediated gene delivery system is expected to be an effective approach for S. zeamais control.

Mitochondrial coding genes mediate insecticide tolerance in the oriental fruit fly, Bactrocera dorsalis (Hendel)

The oriental fruit fly, Bactrocera dorsalis (Hendel), an invasive insect pest infesting fruits and vegetables, possesses a remarkable capacity for environmental adaptation. The investigation of behind mechanisms of the stress adaptability in B. dorsalis holds significantly practical relevance. Previous studies on the molecular mechanism underlying stress resistance in B. dorsalis have predominantly focused on nuclear-coding genes, with limited exploration on organelle-coding genes. In this study, we assessed alterations in the mitochondrial physiological parameters of B. dorsalis under exposure to malathion, avermectin, and beta-cypermethrin at LD50 dosages. The results showed that all three insecticides were capable of reducing mitochondrial complex IV activity and ATP content. Expression patterns of mitochondrial coding genes across different developmental stages, tissues and insecticide exposures were analyzed by RT-qPCR. The results revealed that these mitochondrial coding genes were expressed in various tissues and at different developmental stages. Particularly noteworthy, atp6, cox2, and cytb exhibited substantial up-regulation in response to malathion and avermectin treatment. Furthermore, RNAi-mediated knockdown of atp6 and cox2 resulted in the increased toxicity of malathion and avermectin against B. dorsalis, and cox2 silencing was also associated with the decreased complex IV activity. These findings suggest that atp6 and cox2 most likely play pivotal roles in mediating tolerance or resistance to malathion and avermectin in B. dorsalis. Our results provide novel insights into the role of mitochondrial coding genes in conferring tolerance to insecticides in B. dorsalis, with practical implications for controlling this pest in the field.

Transcriptome analysis of Euwallacea interjectus reveals differentially expressed unigenes related to developmental stages and egg laying

Euwallacea interjectus (Curculionidae: Scolytinae) is an ambrosia beetle species in its early stages of research. Therefore, studying the related molecular mechanism associated with the development and egg laid is essential. Transcriptome sequencing was used in this study to compare the gene expression of the beetles at different developmental stages and female adults before and after oviposition. A total of 40,047 annotated unigenes were obtained. There were 4225 differentially expressed unigenes (DEUs) from larva to prepupa stage, 3651 DEUs between prepupa and pupa, 1675 DEUs generated from pupa to adult, and 4762 DEUs between females before and after oviposition. The most significant pathway differences between different development stages and before and after oviposition were selected through functional annotation of DEUs between different stages. Among them, there were many pathways related to protein metabolism including: neuroactive ligand-receptor interaction, endoplasmic reticulum and RNA transport. This study provides valuable information on the molecular regulation mechanism of development and the egg laid of E. interjectus.