MiR-2b-3p Downregulated Expression in the Larval Midgut to Decrease Cry1Ac Susceptibility of the Diamondback Moth, (L.).

Crystal (Cry) toxins, produced by , are widely used as effective biological pesticides in agricultural production. However, insects always quickly evolve adaptations against Cry toxins within a few generations. In this study, we focused on the Cry1Ac protoxin activated by protease. Our results identified as a trypsin gene that plays a key role in Cry1Ac virulence in larvae. In addition, miR-2b-3p, a member of the micoRNA-2 (miR-2) family, was significantly upregulated by Cry1Ac protoxin and targeted to downregulated its expression. The mRNA level of PxTrypsin-9, regulated by miR-2b-3p, revealed an increased tolerance of larvae to Cry1Ac at the post-transcriptional level. Considering that miR-2b and trypsin genes are widely distributed in various pest species, our study provides the basis for further investigation of the roles of miRNAs in the regulation of the resistance to Cry1Ac and other insecticides.