The proteomic landscape of fall armyworm oral secretion reveals its role in plant adaptation

Abstract BACKGROUND The fall armyworm (FAW, Spodoptera frugiperda (J.E. Smith)) is a polyphagous agricultural pest with rapidly evolving adaptations to host plants. We found the oral secretion (OS) of FAW from different plants influences plant defense response differentially, suggesting its role in adapting to host plants. However, the protein expression profile of FAW OS respond to different plants is largely unknown. RESULTS Here, from the mass spectrometry assay, we identified a total of 256 proteins in the OS of FAW fed on cotton ( Gossypium hirsutum L.), tobacco ( Nicotiana benthamiana Domin), maize ( Zea mays L.) and artificial diet. The FAW OS primarily comprise of 60 proteases, 32 esterases and 92 non‐enzymatic proteins. It displays high plasticity across different diets. We found that more than half of the esterases are lipases which have been reported as insect elicitors to enhance plant defense response. The lipase accumulation in cotton‐fed larvae was the highest, followed by maize‐fed larvae. In the presence of lipase inhibitors, the enhanced induction on defense genes in wounded leaves by OS was attenuated. However, the putative effectors were most highly accumulated in the OS from FAW larvae fed on maize compared to those fed on other diets. We identified that one of them (VRLP4) reduces the OS‐mediated induction on defense genes in wounded leaves. CONCLUSION Together, our investigation presents the proteomic landscape of the OS of FAW influenced by different diets and reveals diet‐mediated plasticity of OS is involved in FAW adaptation to host plants. © 2024 Society of Chemical Industry.