Susceptibility of Hyphantria cunea larvae to Beauveria bassiana under Cd Stress: An integrated study of innate immunity and energy metabolism

Biological control is widely used for integrated pest management. However, there are many abiotic factors that can affect the biocontrol efficiency. In this study, we investigated the susceptibility of Hyphantria cunea larvae to Beauveria bassiana under Cd stress, and the corresponding mechanism was analyzed around innate immunity and energy metabolism. The results showed that mortality of H. cunea larvae treated with Cd and B. bassiana was significantly higher than those treated with B. bassiana alone, and the combined lethal effect exhibited a synergistic effect. Compared with the single fungal treatment group, the total hemocyte count in the combined Cd and fungal treatment group decreased significantly, accompanied by a decrease in phagocytosis, encapsulation, and melanization activity. The expression levels of three phagocytosis-related genes, one encapsulationpromoting gene, and one melanization-regulating gene were significantly lower in the combined treatment group than those in the single fungal treatment group. Furthermore, pathogen recognition ability, signal transduction level, and immune effector expression level were weaker in the combined treatment group than those in the single fungal treatment group. The expression levels of 14 key metabolites and 7 key regulatory genes in glycolysis and tricarboxylic acid cycle pathways were significantly lower in the combined treatment group than those in the single fungal treatment group. Taken together, the weakness of innate immunity and energy metabolism in response to pathogen infection resulted in an increased susceptibility of H. cunea larvae to B. bassiana under Cd pre-exposure. Microbial insecticide is a preferred strategy for pest control in heavy metalpolluted areas. Availability of data and material: All the data that support the findings of this study are available in the manuscript.