No abstract

MicroRNAs play critical roles in post-transcriptional regulation of gene expression, which participate in the modulation of almost all of the cellular processes. Although emerging evidence indicates that microRNAs are related with antineoplastic drugs resistance, whether microRNAs are responsible for insecticide resistance in mosquitos is poorly understood. In this paper, we found that miR-285 was significantly upregulated in the deltamethrin-resistant strain of Culex pipiens pallens, and overexpression miR-285 through microinjection increased mosquito survival rate against deltamethrin treatement. Using bioinformatic software, quantitative reverse transcription PCR, luciferase reporter assay and microinjection approaches, we conformed that CYP6N23 was the target of miR-285. Lower expression of CYP6N23 was observed in the deltamethrin-resistant strain. While, mosquito mortality rate was decreased after downregulating expression of CYP6N23 by dsRNA against CYP6N23 or miR-285 mimic microinjection. These findings revealed that miR-285 could target CYP6N23 to regulate pyrethroid resistance, providing new insights into mosquito insecticide resistance surveillance and control.

Cuticular proteins (CPs) are implicated in insecticide resistance in mosquito populations. Here, we investigated the role of cuticular genes in regulation of insecticide resistance in Culex pipiens pallens. We identified two CpCPRs (CpCPR63 and CpCPR47) that exhibited higher transcript levels in pyrethroid-resistant strains than in susceptible strains. Mosquito mortality was increased after knockdown of CpCPR genes by dsRNA injection. The RNA interference experiment suggested an interaction between CpCPR63 and CpCPR47, as silencing of one gene resulted in decreased expression of the other. These findings revealed that CpCPRs may regulate pyrethroid resistance and could be used as a potential genetic marker to monitor pyrethroid resistance in mosquitoes.

Piwi-interacting RNAs (piRNAs) are a newly identified class of small noncoding RNAs. They are associated with chromatin organization, messenger RNA stability, and genome structure. Although the overexpression of piRNA-3312 in deltamethrin-susceptible (DS) strain of Culex pipiens pallens (L.) was observed in our previous large-scale transcriptome data, the roles of piRNA in insecticide resistance have not been clearly defined. The aim of the present study was to investigate how piRNA-3312 is involved in insecticide resistance. The lower expression level of piRNA-3312 in deltamethrin-resistant (DR) strain of Cx. pipiens pallens was confirmed by quantitative real time polymerase chain reaction (qRT-PCR). Overexpression of piRNA-3312 in the DR strain made the mosquitoes more sensitive to deltamethrin, whereas inhibiting the expression of piRNA-3312 in the DS strain made the mosquitoes more resistant to deltamethrin. Piwi-interacting RNA-3312 was also found to bind 3' UTR (Untranslated Regions) of gut esterase 1 gene and could induce its degradation. In addition, knockdown of gut esterase 1 gene increased the sensitivity of DR strain to deltamethrin. In conclusion, we found that piRNA-3312 targeted the gut esterase 1 gene to negatively regulate the insecticide resistance. This finding facilitates the understanding of various functions of piRNAs and their association with insecticide resistance.

Piwi-interacting RNAs (piRNAs) are a novel class of noncoding single-strand RNAs. They play an important role in the germ cell maintenance, brain development, epigenetic regulation of cancer, and antiviral function. However, little is known about the relationship between the piRNAs and insecticide resistance in mosquitoes. In this study, we reported that piRNA-3878 was related with pyrethroid resistance in Culex pipiens pallens. The expression level of piRNA-3878 was lower in both laboratory and field-collected deltamethrin-resistant (DR) strains. Overexpression of piRNA-3878 increased the susceptibility of the DR strain, while inhibiting the expression of piRNA-3878 in DS strain made the mosquitoes more resistant to deltamethrin. Furthermore, we identified that CpCYP307B1 was the target of piRNA-3878. The mosquito mortality rate was increased after downregulating the expression of CpCYP307B1. These findings revealed that piRNA-3878 could target CpCYP307B1 to regulate pyrethroid resistance.