Mechanisms of pyrethroid resistance in Culicidae mosquitoes from Hainan Island, China

BackgroundMosquito-borne diseases represent critical global public health threats. Insecticide-based prevention and interventions remain essential for disease and vector management. However, insecticide resistance in mosquitoes threatens the effectiveness of these management measures. This study investigated the susceptibility to pyrethroid insecticides and associated resistance mechanisms in five dominant mosquito populations on Hainan Island, China.MethodsWorld Health Organization (WHO) tube bioassays were conducted to evaluate insecticide resistance profiles in Aedes albopictus, Culex quinquefasciatus, Armigeres subalbatus, Aedes aegypti, and Culex tritaeniorhynchus. We assessed the synergistic effects of pre-exposure to 4% piperonyl butoxide (PBO) on deltamethrin mortality rates in Aedes albopictus and Culex quinquefasciatus populations. We genotyped kdr alleles at codon 1534 of the voltage-gated sodium channel gene in Ae. albopictus and at codon 1014 in Cx. quinquefasciatus.ResultsAll five mosquito species exhibited significant resistance to pyrethroid insecticides. Ae. albopictus populations from seven localities were resistant to 0.25% permethrin, 0.03% deltamethrin, and 0.03% alpha-cypermethrin, with mortality rates ranging from 0% to 35.0%, 4.0% to 51.0%, and 2.0% to 27.0%, respectively. Similarly, Cx. quinquefasciatus populations from five sites demonstrated resistance to 0.25% permethrin, 0.4% deltamethrin, and 0.5% alpha-cypermethrin, with all mortality rates below 90%. Three Armigeres subalbatus populations also exhibited resistance to permethrin, deltamethrin, and lambda-cyhalothrin, with one population showing probable resistance to deltamethrin. Pre-exposure to 4% PBO significantly increased mortality rates in both Ae. albopictus and Cx. quinquefasciatus compared with mosquitoes exposed to deltamethrin alone. However, PBO pre-exposure only partially restored the susceptibility of the mosquitoes to pyrethroids. Molecular analysis revealed a higher frequency of kdr mutations (F1534C and F1534S) in resistant Ae. albopictus (mean 67.6% ± 24.3%) compared with susceptible mosquitoes (mean 31.6% ± 12.4%) across four of the five populations. For Cx. quinquefasciatus, the kdr mutation frequency was significantly greater in resistant mosquitoes (mean 82.9% ± 15.0%) than in susceptible mosquitoes (mean 52.8% ± 32.6%).ConclusionsThe results indicated potential multiple resistance mechanisms in mosquitoes in Hainan and highlight the need for systematic monitoring and mapping of insecticide resistance. Innovative mosquito control strategies are needed to support the development and implementation of effective, evidence-based vector control programs.Graphical Abstrac

Author Correction: Bacterial and fungal gut communities of Agrilus mali at different developmental stages and fed different diets

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.</jats:p

Effects of tutin and its derivatives on GAD and GABA-T in Pseudelatia separata (Lepidoptera: Noctuidae)

Tutin inhibits the receptors of the neurotransmitter γ-aminobutyric acid (GABA). In this work, we compared tutin with its derivatives, 2-(4-methoxybenzoyloxy)-tutin (T1), 2-(3,5-dinitrobenzoyloxy)-tutin (T2), 2-(6-chloronicotinoyloxy)-tutin (T3), and 2-(4-nitrobenzoyloxy)-tutin (T4), in terms of their effects on feeding and the feedback regulation mechanism of GABA metabolism. Spectrophotometry was used to determine the glutamic acid decarboxylase (GAD) and γ-aminobutyric acid transaminase (GABA-T) activities of these compounds in 3rd instar larvae of Pseudelatia separata. Clear antifeedant activities were manifested by T1 and especially T3, whereas T4 stimulated feeding in P. separata. GAD and GABA-T activities in larvae treated with all five toxins differed significantly from the control and from one other (P &lt; 0.05) in terms of treatment types and exposure times. The effects of the toxins on GAD and GABA-T were time-dependent for 48 h. GAD activities were inhibited by tutin, T2, T3, and T4, and were enhanced by T1. GABA-T activities were increased by all the toxins in varying degrees. Variation of GABA content in P. separata larvae resulted from the disturbance of GAD and GABA-T by tutin and its derivatives. Results suggest that T3, with its nicotinoyl group, is the most promising novel active ingredient for pest control.</jats:p

Tunable antenna radome based on graphene frequency selective surface

In this paper, a graphene-based frequency selective surface (FSS) is proposed. The proposed FSS exhibits a tunable bandpass filtering characteristic due to the alterable conductivity of the graphene strips which is controlled by chemical potential. Based on the reconfigurable bandpass property of the proposed FSS, a cylindrical antenna radome is designed using the FSS unit cells. A conventional omnidirectional dipole can realize a two-beam directional pattern when it is placed into the proposed antenna radome. Forward and backward endfire radiations of the dipole loaded with the radome is realized by properly adjusting the chemical potential. The proposed antenna radome is extremely promising for beam-scanning in terahertz and mid-infrared plasmonic devices and systems when the gain of a conventional antenna needs to be enhanced

Effects of Nutrient Elements on Growth and Expression of Insect-Defense Response Genes in Zanthoxylum bungeanum Maxim

In China, Zanthoxylum bungeanum Maxim, known as &ldquo;Huajiao,&rdquo; has a pleasant, fragrant flavor and several therapeutic properties. The nutritional content of plants is necessary for their defense response to insects. In this study, we analyzed the effects of soil fertilization treatments such as nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and special compound fertilizer for pepper (HZ) on the different growth parameters and expression of insect-defense-response genes in Z. bungeanum. The results show that the height and weight of prickly ash significantly differed after the application of fertilizers with different concentrations. Additionally, seedlings that were treated with low concentrations of nutrient fertilizers (N1, P1, K1, Ca1, and HZ1) were significantly higher, and they were selected for transcriptome analysis. According to transcriptomic analysis, a total of 65,566 unigenes were discovered, among which 61,379 corresponded to annotated protein-coding genes and 4187 to transcripts of novel protein-coding genes. A total of 294 unigenes were detected as candidate genes for regulating the defense response to insects, including 204 protease inhibitors, 29 plant lectins, and 61 other defense response genes. Additionally, trypsin inhibitors, cystatin, phytepsin, metalloproteinase, MMP, caffeic acid, resveratrol, and thiol proteinase inhibitors, ACA, TDC, and 28 BES1 were enriched in Z. bungeanum. Specifically, the leaves of Z. bungeanum that were treated with Ca and HZ fertilizations were dominated by the protease inhibitors. In addition, the type of fertilizer significantly affects gene expression in plants. The functional annotations were predicted by the number of differentially expressed genes and classified by GO and KEGG ontology enrichment analysis. Moreover, according to the GO database, biological processes were the largest group and contained a high frequency of differentially expressed genes. According to KEGG pathway results, significantly enriched genes belonged to the biosynthesis of secondary metabolisms, amino acid metabolism, and folding, sorting, and degradation. Overall, it was found that the type of fertilizer with low concentrations had an effect on Z. bungeanum&rsquo;s primary and secondary metabolism, and these findings provided grounds for further research in forest protection science