Identification and expression analysis of GST genes in response to quercetin induction in Hyphantria cunea

Objective Glutathione S-transferases (GSTs) are important detoxification enzymes in insects, playing an important role in the physiologhical adaptation of phytophagous insects to plant secondary substances. In this study, we screened and identified GST genes and analyzed their expression patterns induced by quercetin in Hyphantria cunea midgut, laying the foundation for elucidating the function of GST genes in detoxification and metabolism of quercetin in H. cunea.

Method Based on the quercetin-induced midgut transcriptome of H. cunea, the GST genes in response to quercetin induction were screened and identified. The family categories of GST genes were analyzed by constructing phylogenetic tree. The dose effect and time effect of quercetin on GST gene induction were studied by real-time fluorescence quantitative PCR.

Result Six GST genes were identified from the gut in response to quercetin induction. Phylogenetic analysis showed that HcGST-E1, HcGST-E2 and HcGST-E3 belong to the GST Epsilon family, HcGST-S1 and HcGST-S2 belong to the GST Sigma family, and HcGST-O1 belongs to the GST Omega family. Various mass fraction of quercetin had different induction effects on GST genes. The tested mass fraction of quercetin (0.5%, 1.0%, 2.0% and 4.0%) significantly up-regulated HcGST-E1 expression, below 2.0% of quercetin significantly increased HcGST-E3 expression, and 0.5% quercetin significantly enhanced HcGST-O1 expression. By contrast, the tested mass fraction of quercetin significantly induced the down-regulation of the expression level of HcGST-S1 and 0.5% and 1.0% of quercetin significantly down-regulated the expression level of HcGST-S2. Three up-regulated GST genes were significantly up-regulated within 24 h or 36 h by quercetin.

Conclusion Quercetin could significantly induce the expression levels of six GST genes in the midgut of H. cunea, but the expression patterns are various for each induced gene. HcGST-E1, HcGST-E3 and HcGST-O1 are significantly up-regulated in response to the quercetin induction. It is, therefore, speculated that these 3 genes are the key genes involved in the detoxification of quercetin in H. cunea.