Function of Tryptophan 2,3-Dioxygenase in Monochamus alternatus Hope Revealed by RNA Interference

Monochamus alternatus Hope (Coleoptera: Cerambycidae), an invasive beetle that has caused billions of dollars of economic losses, is a serious pest of Pinus massoniana in many Asian countries. An efficient RNAi system is helpful for functional genomics research on M. alternatus. In this study, a tryptophan 2,3-dioxygenase (TDO) related to the ommochrome synthesis in insects was identified. Using RNAi technology, the M. alternatus TDO gene was silenced by injecting dsRNA into pupae, and individuals were analyzed by phenotype and expression of the TDO gene by RT-qPCR. The results show that TDO is expressed in different developmental stages of M. alternatus, having its peak expression during the prepupal stage. White-eye phenotypes were observed in the pupal and adult stages after dsRNA injection, and a significant 81% decrease in TDO mRNA levels 48 h after injection was determined by RT-qPCR. This gene can be used as a genetic marker and is an important discovery for future genetic engineering tools to control M. alternatus populations.