Abstract: 【Aim】 The nucleases in the digestive system of Lepidoptera are one of the main reasons for the low efficiency of RNAi. This study aims to explore the effects of RNAi efficiency-related nuclease (REase) of Bombyx mori BmREase on the low efficiency of RNAi in B. mori. 【Methods】 The full-length cDNA sequence of BmREase was homologously cloned from B. mori by RT-PCR and bioinformatically analyzed, and phylogenetic analysis was carried out by maximum likelihood method. qRT-PCR was used to detect the specific expression of BmREase in different tissues (head, cuticle, fat body, midgut, trachea, Malpighian tubules and silk gland) of B. mori at the wandering stage. Furthermore, by injecting the dsRNAs of BmREase, ecdysone receptor (EcR) gene BmEcR, ultraspiracle (USP) gene BmUSP and cytokine sp-tzle1 (Spz1) gene BmSpz1 of B. mori into the wandering B. mori for RNAi, we analyzed whether interferring the expression of BmREase can improve the interference efficiency of dsRNAs of target genes.【Results】The full-length cDNA sequence of BmREase (GenBank accession no.: XM_021350017.2) of B. mori was obtained by RT-PCR amplification. The open reading frame of BmREase is 2 241 bp in length, encoding 746 amino acid residues. Bioinformatics analysis showed that BmREase has a very similar structure to human exonuclease I 3qe9.1, and the active domain composed of Thr7, His33, Ala37, Arg93, Lys97, Tyr159, Asp160, Ser161 and Asn174 can bind to the nucleic acid sequence, indicating that BmREase has nuclease activity. qRT-PCR results showed that BmREase was highly expressed in the wandering midgut and Malpighian tubules of B. mori, indicating that the nuclease mainly exists in the digestive system of B. mori. The expression level of BmREase in the wandering B. mori injected with dsRNA was higher than that of the blank control group. When BmREase was interfered by RNAi, the interference efficiency of dsBmEcR, dsBmUSP and dsBmSpz1 were increased.【Conclusion】 BmREase, which has a similar function to human exonuclease, may affect the interference efficiency of dsRNA in B. mori. This study is instructive for using RNAi to study the gene function of B. mori and to further develop RNAi for pest control.

Key words: Bombyx mori, RNA interference, dsRNA, RNAi efficiency-related nuclease; BmREase, dsRNA exonuclease