Detecting the Role of Salivary Protein Genes in <i>Spodoptera frugiperda</i> Adaptation to Different Host Plants

<i>Spodoptera frugiperda</i> possesses a remarkably broad host range and causes substantial economic losses in global agricultural production. Insect saliva secreted onto plant surfaces plays a vital role in regulating both plant defense responses and insect adaptation. However, the mechanisms by which <i>S. frugiperda</i>salivary proteins that respond to plant defense responses and regulate host adaptation remain elusive. The two-sex life table evaluation indicates that the host adaptability of <i>S. frugiperda</i> varies under different feeding schemes. Transcriptome analysis of differentially expressed genes in the salivary glands revealed that <i>PTL</i>, <i>CSP2</i>, and <i>SPI</i> are specifically responsive to host plants but not to an artificial diet. In <i>S. frugiperda</i> fed on adaptive host plants, the primary secretory proteins PDI and esterase FE4 are involved in enhancing host adaptation. When fed on nonadaptive host plants, <i>S. frugiperda</i> invests more energy in synthesizing detoxification metabolic enzymes such as trypsin, SPSL, and CLE2A. This study offers valuable insights into the adaptation mechanisms of phytophagous insects and identifies candidate genes involved in insect-plant interactions, offering targets for sustainable pest control strategies.