Cellular secretion of hydrolases from entomopathogenic Beauveria bassiana ERL836

Entomopathogenic fungal isolates, Beauveria bassiana ERL836 and JEF007, exhibit insecticidal activity against various insect pests. While gene expression in these isolates has been extensively studied using RNA-sequencing, the contribution of fungal peptides to elucidating fungal pathogenesis remains relatively unexplored. This study investigated the peptide profiles of the two fungal supernatants. Supernatants obtained from liquid cultures of ERL836 and JEF007 were evaluated against Tenebrio molitor larvae using spray and feed-supplementation assays. Significantly higher mortality was observed in the ERL836 treatment when applied by spraying, and in the JEF-007 treatment when administered via feed supplementation. Subsequently, the supernatants were subjected to LC/MS-based peptide sequencing and annotation using the UniProt database to analyze differentially expressed peptides (DEPs) between ERL836 and JEF007. The DEP analysis revealed that approximately half of the secreted peptides were more abundant in the ERL836 supernatant, with the remainder more abundant in JEF-007. The highly expressed ERL836 DEPs were primarily enriched in Gene Ontology (GO) terms linked to hydrolase activity-related enzymes. Phylogenetic analysis indicated that ERL836 expressed unique hydrolases with distinct sequences including chitinases, trypsin, and serine protease. Additionally ERL836 highly expressed secretion-related proteins, including signal transduction-related histidine kinase, transmembrane-related protein, and chitinase transcription factor 1β. This study suggests that ERL836 preferentially secretes abundant pathogenesis-related peptides, some of which are unique hydrolases compared to the other B. bassiana isolates. The identification of these virulence-related hydrolases could provide an updated perspective on the fungal mode of action in ERL836.