Screening of lethal genes for feeding RNAi by leaf disc-mediated systematic delivery in Tetranychus urticae

The screening of effective lethal genes was conducted via the systemic delivery of dsRNA for the RNA interference (RNAi)-based management of Tetranychus urticae. Four candidate genes (ß subunit of coatomer protein complex, T-COPB; M1 metalloprotease, T-M1MP; Ribosomal protein S4, T-RPS4; A subunit of V-ATPase, T-VATPase) with a reference gene (EGFP) were tested for the experiment. The permeated dsRNA to the leaf disc (ca. 15-mm diameter) was detected at 12 h post-treatment, indicating that dsRNA could move through veins on the leaf. In the evaluation of toxicity, dsRNA treatment of the T-COPB, T-M1MP, T-RPS4 and T-VATPase exerted 65.4%, 15.9%, 36.1% and 21.1% mortalities at 120 h post-treatment, respectively. Reduction of all target gene transcripts following dsRNA treatment was confirmed by quantitative PCR, demonstrating that RNAi based on feeding dsRNA could kill T. urticae. In summary, the dsRNA delivery via leaf disc was effective in screening lethal genes and some genes, such as T-COPB, T-M1MP, T-RPS4 and T-VATPase, can be applicable for establishing a RNAi-based control system against T. urticae.