In-vitro-expressed pxy-mir-34 shows high toxicity to multiple lepidopteran pests

Lepidopteran pests cause enormous economic losses to agriculture globally. The control of these pests relies heavily on chemical insecticides, resulting in severe insecticide resistance and food safety concerns. Therefore, there is an urgent need to develop alternative green strategies. Our previous research revealed that the miRNA of the diamondback moth Plutella xylostella, pxy-miR-34-5p, may be a novel molecular target for multiple lepidopteran pests. However, the application strategy for pxy-miR-34-5p is not yet clear. In this study, pxy-mir-34 was successfully expressed in Escherichia coli to produce artificial miR-34 (amiR-34) on a large scale. Treatment with amiR-34 significantly repressed the expression of the ecdysone receptor (EcR) and 12 other key genes involved in the growth and development of P. xylostella. Feeding bioassays showed that amiR-34 was highly toxic to multiple lepidopteran pests, and pot experiments demonstrated that spraying with amiR-34 led to larval mortalities of 81.7%, 89.3%, and 90.8% for P. xylostella, Spodoptera frugiperda, and Spodoptera exigua, respectively, with a persistence of up to five d. These results indicate that amiR-34 has great potential for controlling multiple lepidopterous pests and they lay an important foundation for developing miRNA-based green pest control strategies.