Genomic and Transcriptomic Analysis Reveals Cuticular Protein Genes Responding to Different Insecticides in Fall Armyworm Spodoptera frugiperda

SIMPLE SUMMARY: The fall armyworm (FAW), Spodoptera frugiperda, is a notorious agricultural pest worldwide, causing great damage to a wide variety of crops. This pest exhibited a remarkable field-evolved resistance to multiple insecticides. According to the evidence, a few cuticular proteins (CPs) participate in the insecticide resistance of several insects. This study was designed to explore whether CP genes of the FAW exhibit functional roles in responding to insecticides stress. There are a set of CP genes significantly regulated in response to the exposure to different insecticides, implying that CP genes play an important role in the FAW against insecticides stress. The results inspire further functional validation of CP genes in FAWs to gain a better understanding of its resistance to insecticides. ABSTRACT: The fall armyworm (FAW), Spodoptera frugiperda, is a serious pest of crucial crops causing great threats to the food security of the world. It has evolved resistance to various insecticides, while the underlying molecular mechanisms remain largely unknown. Cuticular proteins (CPs), as primary components in cuticle, play an important role in insects’ protection against environmental stresses. Few of them have been documented as participating in insecticide resistance in several insect species. In order to explore whether CP genes of the FAW exhibit a functional role in responding to insecticides stress, a total of 206 CPs, classified into eight families, were identified from the genome of the FAW through a homology-based approach coupled with manual efforts. The temporal expression profiles of all identified CP genes across developmental stages and their responses to 23 different insecticides were analyzed using the RNA-seq data. Expression profiling indicated that most of the CP genes displayed stage-specific expression patterns. It was found that the expression of 51 CP genes significantly changed after 48 h exposure to 17 different insecticides. The expression of eight CP genes responding to four insecticides were confirmed by RT-PCR analysis. The results showed that their overall expression profiles were consistent with RNA-seq analysis. The findings provide a basis for further functional investigation of CPs implied in insecticide stress in FAW.