Horizontally transferred genes as natural and specific RNAi targets in a pest spider mite (Panonychus citri)

RNAi has great potential as a novel strategy to control spider mite pests without targeting natural control agents such as predatory mites. To achieve this, an efficient RNAi target gene for spider mite control must also be ineffective against non-target predatory mites. Several genes obtained through horizontal gene transfer (HGT) have been shown to facilitate the adaptation of spider mites and thus fit the requirement of specific RNAi targets; however, comprehensive analyses of HGT genes in spider mites are still rare. Here, we identified and investigated the potential of HGT genes as RNAi targets in a key spider mite, Panonychus citri. A total of 78 HGT genes were identified with no evidence of homol- ogy in predatory mites. RNAi of six selected genes resulted in significant mortalities ranging from 50.7 to 68.5%, with RNAi of intradiol ring cleavage dioxygenase 1 (PcIDR1) resulting in the highest mortality. To test the specificity of HGT genes as RNAi targets, we predicted the off-target sites of PcIDR1 in the predatory mite Neoseiulus barkeri and tested their response to dsPcIDR1. Ingestion of dsPcVATPase, a commonly used RNAi target, but not dsPcIDR1 disrupted off-target genes and the predatory response of N. barkeri. In conclusion, our study demonstrates that HGT genes can serve as natural and specific RNAi targets for spider mite control without adverse effects on predatory mites.

Automated summary

RNAi has the potential to control spider mite pests without harming natural predators. This study identified and investigated HGT genes as potential RNAi targets for spider mite control. The results showed that these genes can be used as natural and specific RNAi targets without adverse effects on predatory mites.