Functional study of the MsCYP9A319 in Micromelalopha sieversi in response to tannic acid stress.

Micromelalopha sieversi (Staudinger) is a major forest pest causing severe damage to poplar plantations in China. However, the molecular mechanisms underlying its adaptation to plant secondary metabolites remain largely unclear. In this study, a P450 gene designated MsCYP9A319 was screened from tannic acid-induced transcriptomes of M. sieversi and cloned. Sequence analysis revealed that MsCYP9A319 belongs to the CYP9 family and contains typical conserved domains of cytochrome P450 proteins. Real-time quantitative polymerase chain reaction (RT-qPCR) assays showed that MsCYP9A319 was highly expressed in the midgut and head of larvae, with the highest expression level in the 3rd instar, and was significantly induced by 0.1 mg/mL tannic acid. In addition, we performed molecular docking experiments, and the results indicated that MsCYP9A319 exhibited strong binding affinity to tannic acid, providing further evidence that this protein can specifically recognise tannic acid as its substrate. Furthermore, RNAi-mediated silencing of MsCYP9A319 significantly decreased larval tolerance to tannic acid. These results indicate that MsCYP9A319 participates in the response of M. sieversi to tannic acid stress, and provide a theoretical basis for elucidating host adaptation mechanisms and screening target genes for green pest control.