Identification and expression of detoxification genes provide insights into host adaptation of the walnut pest Atrijuglans aristata.

BACKGROUND

Despite the presence of a large number of toxic components, primarily juglone, in walnut green husks, these components have failed to prevent infestations of the specialized pest Atrijuglans aristata. At present, it remains unclear whether detoxification genes play a pivotal role in enhancing host fitness of A. aristata. In this study, we explored the adaptation mechanisms of A. aristata to host plants by identifying and expressing gene families associated with detoxification, as well as assessing the binding affinity of their protein products with juglone.

RESULTS

We identified 84 P450 (P450 monooxygenases), 48 COE (carboxylesterases), 34 GST (glutathione S-transferases), 26 UGT (UDP-glycosyltransferases), and 57 ABC (ATP-binding cassette) transporter genes in the genome of A. aristata. The P450 gene family of A. aristata was divided into four classes based on phylogenetic relationships. Comparative transcriptome analysis revealed that 383 genes in the larval guts of A. aristata were significantly down-regulated after starvation treatment compared with normal feeding. These genes were frequently enriched in pathways related to P450 detoxification metabolism. Through homology modeling and molecular docking analysis of the 12 significantly down-regulated P450 genes, it was found that all 12 proteins exhibited strong binding affinities with the ligand molecule juglone.

CONCLUSIONS

The gene number of the detoxification-related families in the A. aristata genome is close to that of other specialized insect species. Twelve candidate P450 genes identified in comparative transcriptome analysis are inferred to be involved in host adaptation of A. aristata. These results provide a theoretical basis for the management of walnut pests.