Cytochrome P450s Are Essential for Insecticide Tolerance in the Endoparasitoid Wasp Meteorus pulchricornis (Hymenoptera: Braconidae)

With the widespread application of insecticides, parasitoid wasps may also be under risk when exposed to insecticides directly at their free-living stages. The endoparasitoid wasp Meteorus pulchricornis is the predominant natural enemy of many lepidopteran pests, such as Spodoptera litura and Helicoverpa armigera. The cytochrome P450 monooxygenases constitute a ubiquitous and complex superfamily of hydrophobic, haem-containing enzymes. P450s are involved in the detoxification of many xenobiotics. However, their exact roles in the tolerance mechanism in parasitoids toward insecticides has received less attention. Here, 28 P450 genes in M. pulchricornis were identified from a previously constructed transcriptome dataset. These P450 genes belonged to CYP2, -3, and -4, and mitochondrial clans. Subsequently, eight candidate MpulCYPs were selected from four CYP clans to validate their expression patterns under phoxim, cypermethrin, and chlorfenapyr exposure by qRT-PCR. The results showed that all three insecticides had significant effects on the expression of MpulCYPs. To further study the function of P450s, CYP369B3 was silenced, and its expression levels of CYP369B3 were significantly decreased. Survival analysis indicated that after dsRNA injection, the mortality rate of wasps was significantly increased when M. pulchricornis females were exposed to insecticides compared to control groups. Our findings provide a theoretical base for elucidating the mechanism of insecticide tolerance and promote functional research on P450 genes in parasitoid wasps.

Second generation effects of larval metal pollutant exposure on reproduction, longevity and insecticide tolerance in the major malaria vector Anopheles arabiensis (Diptera: Culicidae)

Background Members of the Anopheles gambiae complex breed in clean, sunlit temporary bodies of water. Anthropogenic pollution is, however, altering the breeding sites of the vectors with numerous biological effects. Although the effects of larval metal pollution have previously been examined, this study aims to assess the transgenerational effects of larval metal pollution on the major malaria vector An. arabiensis. Methods Two laboratory strains of An. arabiensis, SENN (insecticide-susceptible) and SENN-DDT (insecticide-resistant), were used in this study. After being bred in water polluted with either cadmium chloride, copper nitrate or lead nitrate, several life history characteristics that can have epidemiological implications (fertility, apoptotic damage to reproductive structures, adult longevity and insecticide tolerance) were examined in the adults and compared to those of adults bred in clean water. Results All metal treatments reduced fecundity in SENN, but only lead treatment reduced fertility in SENN-DDT. Cadmium chloride exposure resulted in apoptosis and deformation of the testes in both strains. After breeding generation F0 in polluted water, F1 larvae bred in clean water showed an increase in longevity in SENN-DDT adult females. In contrast, after breeding the F0 generation in polluted water, longevity was reduced after cadmium and copper exposure in the F1 generation. Larval metal exposure resulted in an increase in insecticide tolerance in adults of the SENN strain, with SENN-DDT adults gaining the greatest fold increase in insecticide tolerance. Conclusions This study demonstrates that a single exposure to metal pollution can have transgenerational effects that are not negated by subsequent breeding in clean water.

Transcriptome Analysis and Identification of Insecticide Tolerance-Related Genes after Exposure to Insecticide in Sitobion avenae

Aphids cause serious losses to the production of wheat. The grain aphid, Sitobion avenae, which is the dominant species of aphid in all wheat regions of China, is resistant to a variety of insecticides, including imidacloprid and chlorpyrifos. However, the resistance and mechanism of insecticide tolerance of S. avenae are still unclear. Therefore, this study employed transcriptome analysis to compare the expression patterns of stress response genes under imidacloprid and chlorpyrifos treatment for 15 min, 3 h, and 36 h of exposure. S. avenae adult transcriptome was assembled and characterized first, after which samples treated with insecticides for different lengths of time were compared with control samples, which revealed 60–2267 differentially expressed unigenes (DEUs). Among these DEUs, 31–790 unigenes were classified into 66–786 categories of gene ontology (GO) functional groups, and 24–760 DEUs could be mapped into 54–268 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Finally, 11 insecticide-tolerance-related unigenes were chosen to confirm the relative expression by quantitative real-time polymerase chain reaction (qRT-PCR) in each treatment. Most of the results between qRT-PCR and RNA sequencing (RNA-Seq) are well-established. The results presented herein will facilitate molecular research investigating insecticide resistance in S. avenae, as well as in other wheat aphids.