Identification, genomic organization and expression pattern of glutathione transferase in Pardosa pseudoannulata

The pond wolf spider, Pardosa pseudoannulata, is one of the dominant natural enemies in farmlands and plays important roles in controlling a range of insect pests. The spider is less sensitive to many insecticides than the target pests such as the brown planthopper, Nilaparvata lugens. The different sensitivity to a certain insecticide between species is mostly attributed to the differences in both molecular targets and detoxification enzymes. As one of the most important detoxification enzymes, glutathione transferases (GSTs) play a key role as phase II enzyme in the enzymic detoxification in organisms. Until now, there are few studies on spiders' GSTs, limiting the understanding of insecticide selectivity between insect pests and natural enemy spiders. In this study, based on the transcriptome and genome sequencing of P. pseudoannulata, thirteen full-length transcripts encoding GSTs were identified and analyzed. Interestingly, Delta family, which is thought to be specific to the Insecta, was identified in P. pseudoannulata. Further, vertebrate/mammalian-specific Mu family was also identified in P. pseudoannulata. The mRNA expression levels of cytosolic GSTs in different tissues were determined, and most GST genes were abundant in the gut and the fat body. To investigate GST candidates involving in insecticide detoxification, the mRNA levels of cytosolic GSTs were tested after spiders' exposure to either imidacloprid or deltamethrin. The results showed that PpGSTD3 and PpGSTT1 responded to at least one of these two insecticides. The present study helped understand the function of GSTs in P. pseudoannulata and enriched the genetic information of natural enemy spiders.