Symbiotic bacteria are important drivers of phenotypic diversity in insects. One of the widespread symbionts to have emerged belongs to the genus Arsenophonus, however, its biological functions in most host insects remain entirely unknown. Here we report two distinct Arsenophonus strains in the brown planthopper (BPH), Nilaparvata lugens, a major pest insect in Asian countries that causes significant economic damage through rice crop destruction. Genomic resequencing data suggested that one Arsenophonus strain (S-type) negatively affected the insecticide resistance of the host. Indeed, replacement of the resident Arsenophonus with the S-type Arsenophonus significantly decreased host insecticide resistance. Transcriptome and metabolome analysis revealed down-regulation of xenobiotic metabolism and increased amino acid accumulation in the S-type Arsenophonus infected host. This study demonstrates how a symbiont-mediated phenotypic change can occur. The results of this study will aid in developing strategies that work through imposing an ecological disadvantage on insect pests, which will be of great value for pest control in agricultural industry.

Ingested miR-2703 seems to be a good option for killing N. lugens nymphs, while NlCHSA may be a promising target for RNAi-based pest management. These findings provide important evidence for applications of small non-coding RNAs (snRNAs) in insect pest management. © 2016 Society of Chemical Industry.

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The chitin biosynthesis pathway is an important physiology process in arthropods. However, few microRNAs (miRNAs) involved in the regulation of the chitin biosynthesis pathway in insects have been reported until now. In this study, four groups of samples that either upregulated or downregulated the chitin biosynthesis pathway were collected for deep sequencing, and a total of 15 unique mature miRNAs with significantly different expression levels were found, including 11 known miRNAs and four novel miRNAs. Subsequently, we showed that miR‐2703 and its new target gene chitin synthase 1a are important for ecdysone‐induced chitin biosynthesis in Nilaparvata lugens, a serious insect pest of rice. The nymphs showed an obvious moulting defect phenotype, lower survival rate and significantly reduced chitin content after miR‐2703 feeding or injection. Furthermore, we found that the transcription level of miR‐2703 was not repressed by 20‐hydroxyecdysone signalling after Broad‐Complex (BR‐C) double‐stranded RNA (dsRNA) injection compared with the repressed levels after green fluorescent protein dsRNA injection, suggesting that the involvement of miR‐2703 in the 20‐hydroxyecdysone pathway contributes to BR‐C activity. miR‐2703 regulates the chitin biosynthesis pathway by targeting chitin synthase 1a in response to 20‐hydroxyecdysone signalling.

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Landfill accumulation can cause its leachate to seep into groundwater, which can lower the quality of local groundwater. Exploring the risks of groundwater contamination to human health in the area around a landfill can offer a clear understanding of the current situation of regional groundwater and provide a theoretical basis for groundwater remediation and governance. By taking a landfill in Kaifeng City, China as the research object, this study explored the chemical types and sources of groundwater in the study area, used the entropy-weighted water quality index (EWQI) to evaluate the groundwater quality and assessed human health risks in the study area. The results show that the groundwater in the study area is neutral (7.14 ≤ pH ≤ 7.86), and the water chemical type is HCO3−—Ca·Na. The EWQI results indicated that the overall water quality in the study area ranges from 48.4 to 250.26, which is above the medium level, and that the local water quality is poor. The deterioration of groundwater quality in the study area is mainly influenced by NH4+-N, Mn, As, F- and Pb. According to the human health risk assessment model, the non-carcinogenic risk to humans through oral and dermal exposure can be assessed. In this paper, five ions, NH4+-N, Mn, As, F- and Pb in groundwater, were selected for the analysis of groundwater in the study area to assess non-carcinogenic risk to humans through oral administration. The results showed that the hazard quotient (HQ) values for NH4+-N, Mn, As, F− and Pb varied in the following ranges: 9.14 × 10−4—0.03; 0.07—0.22; 0.02–0.07; 0.16—0.23; and 0.01—0.13, respectively (all of these are less than 1, and so the potential risks to human health can be ignored). The characteristic pollutant Pb was selected as a predictor to study the influence on groundwater quality in eastern fish ponds and farmlands under continuous leakage. The leakage can be detected timeously to reduce the effects downstream by using enhanced monitoring measures.