Characterization of lipases revealed tissue-specific triacylglycerol hydrolytic activity in Spodoptera frugiperda

Lipids perform a diverse and unique array of functions in insects. Lipases are key enzymes in lipid metabolism, and their metabolic products are crucial for development and reproduction of insects. Here, a total of 110 lipase genes were identified in the genome of Spodoptera frugiperda. Cluster analysis indicated that neutral lipases constitute the majority of lipases. Tissue expression profile analysis displayed that most lipase genes were highly expressed in the larval gut of S. frugiperda. Some lipases exhibited a diet-specific expression pattern, which implied their roles in host adaptation. Key domain analysis proved that none of the neutral lipases highly expressed in the gut has an integrated lid domain, while most lipases highly expressed in the fat body contained both the integrated lid domain and β9 loop, indicating the activity loss of neutral lipases in guts. The assay of triacylglycerol (TAG) hydrolytic activity confirmed that the gut had the lowest activity when compared to that of fat body and epidermis. Interestingly, the opposite TAG hydrolytic activity trends across mating were observed between adult males and females, implying that lipase played different roles in the reproduction of both sexes. In conclusion, neutral lipases lost TAG hydrolytic activity in S. frugiperda guts, but retained the activity in fat body. Neutral lipases would play vital roles in many physiological processes in insects, especially in insect reproduction, which provides palpable targets for novel insecticide development to control insect population growth.