Construction of miR-34-5p maize and its toxicity evaluation against Spodoptera frugiperda larvae

The fall armyworm, Spodoptera frugiperda, is a major agricultural pest with high reproductive potential and poses a significant threat to a wide range of crops. Currently, it has developed resistance to multiple insecticides. Therefore, alternative green control strategies are urgently needed.

Previous research revealed that overexpression or inhibition of microRNA, miR-34-5p, resulted in high mortality in multiple lepidopteran pests such as Spodoptera frugiperda. To further evaluate the potential application of miR-34-5p in pest control, we constructed genetically modified maize expressing miR-34-5p. After the fall armyworm fed on this maize for 96 hours, the expression level of miR-34-5p significantly increased by 2.5 fold, and the expression level of its target gene, the ecdysteroid receptor SfEcR, significantly decreased by 45.5%.

Bioassay results demonstrated that the cumulative mortality of S. frugiperda fed on miR-34-5p transgenic maize were significantly increased by 25.0%~40.0%, compared with that of larvae fed on wild-type maize. Surviving larvae exhibited significant developmental defects and low fecundity.

These results indicate that insect microRNA-based transgenic crops exhibit promising control efficacy against S. frugiperda, which provides a theoretical basis and technical support for the development of miRNA-based green pest control strategies.