In vivo transcriptomic analysis of Beauveria bassiana reveals differences in infection strategies in Galleria mellonella and Plutella xylostella

BACKGROUND Insect pests have evolved various defense mechanisms to combat fungal infection, and fungi have developed multiple strategies to overcome the immune defense responses of insects. However, transcriptomic analysis of fungal strategies for infecting different pests has not been reported. RESULTS Transcriptomic profiling of Beauveria bassiana was performed at 12, 24 and 48 h after infecting Galleria mellonella and Plutella xylostella, and 540, 847 and 932 differentially expressed genes were detected, respectively. Functional categorization showed that most of these genes are involved in the ribosome, nitrogen metabolism and oxidative phosphorylation pathways. Thirty‐one differentially expressed virulence genes (including genes involved in adhesion, degradation, host colonization and killing, and secondary metabolism) were found, suggesting that different molecular mechanisms were used by the fungus during the infection of different pests, which was further confirmed by disrupting creA and fkh2. Virulence assay results showed that ΔcreA and Δfkh2 strains of B. bassiana had distinct fold changes in their 50% lethal time (LT50) values (compared with the control stains) during infection of G. mellonella (ΔcreA: 1.38‐fold > Δfkh2: 1.18‐fold) and P. xylostella (ΔcreA: 1.44‐fold