Signal peptide peptidase serves as a target gene to improve the biological control efficacy of Beauveria bassiana against Lepidopteran insect Bombyx mori

BACKGROUND Pest resistance to chemical and biological control methods remains a persistent challenge. Thus, target genes and resistance‐related mechanisms must be identified to improve control efficiency. Although a large number of studies have been dedicated to enhancing the biological control efficacy of insect pathogenic fungi (such as Beauveria bassiana ), the robust pest immune responses still limit its applicability. We therefore aimed to investigate the role of signal peptide peptidase (SPP) in the resistance of silkworm to B. bassiana . To this end, we examined its impact on chitin synthesis and explored potential metabolic interventions to enhance biological control efficacy against pests. RESULTS SPP‐knockout silkworm ( BmSPP KO ) infected with B. bassiana were susceptible to this fungus. This increased susceptibility was attributed to disruption of the chitin synthesis pathway in the cuticle. BmSPP KO silkworms exhibited reduced expression of genes associated with chitin synthesis, along with decreased hexokinase and glucose 6‐phosphate contents in the epidermis compared to those in B. bassiana ‐infected wild‐type silkworms. This disruption inhibited chitin synthesis in the epidermis, leading to reduced thickness of the chitin layer. However, monosaccharide supplementation reversed this susceptibility phenotype. CONCLUSION This study indicates that the host's SPP is a promising target gene for pest control because disruption of its function can enhance the virulence of B. bassiana . This discovery provides a basis for the broad‐spectrum enhancement synergistic of B. bassiana .