Identification and characterization of an RNAi efficiency-related nuclease in Diatraea saccharalis (Fabr.) (Lepidoptera: Pyralidae)

RNA interference (RNAi) is a conserved mechanism found in all eukaryotes, initiated by the presence of double-stranded RNA (dsRNA) in the cells that leads to the block of protein synthesis of a target gene. RNAi is being explored to develop species-selective biopesticides by delivering insect-specific dsRNA. The application of RNAi methods to control lepidopteran pests is difficult because of their recalcitrance to RNAi. Many studies concluded that degradation of dsRNA by double-stranded ribonucleases (dsRNases) contribute to the variability in RNAi efficiency observed among insects, and it could be one of the factors involved in reducing RNAi efficiency in Lepidoptera. Here, we identified a gene that encodes a protein RNAi efficiency-related nuclease (REase) of the sugarcane borer Diatraea saccharalis, named DsREase. Phylogenetic analysis revealed that this previously uncharacterized protein is homologous to other lepidopteran sequences, including the Ostrinia furnacalis REase, the first one characterized. Bioinformatic predicted analyses showed that this deduced protein contained a PIN domain, characteristic of nuclease proteins. Gene expression analysis revealed that Ds_REase is constantly expressed from the first to the sixth. However, the exposure of D. saccharalis larvae to dsRNA strongly up-regulated DsREase expression. We propose that the occurrence and up-regulation of DsREase by exposure to dsRNA may contribute to D. saccharalis recalcitrance to RNAi, and downregulation of this nuclease activity might improve the RNAi efficiency in D. saccharalis.