Oberti, H. | bioRxiv Science

bioRxiv2025

From omics to enhanced fungal virulence: Overexpression of a putative secreted protein improves Beauveria bassiana biocontrol potential against the insect pests Piezodorus guildinii and Tenebrio molitor

The entomopathogenic fungus Beauveria bassiana is widely used as a biocontrol agent, but its efficacy varies depending on the target insect species. Piezodorus guildinii, a major soybean pest, exhibits low susceptibility to B. bassiana. Thus, biocontrol of this pest requires improving virulence of B. bassiana. Here, we used genomic and transcriptomic analyses to identify novel genes associated with the enhanced virulence of B. bassiana strain ILB308 when exposed to the insect epicuticular hydrocarbon n-pentadecane. Comparative analysis with the lower-virulence strain ILB205 revealed differentially expressed genes (DEGs) linked to genetic information process pathways and immune evasion. Among these DEGs, we identified BbCBM9_1, a secreted carbohydrate-binding protein, as a candidate virulence factor. Overexpression of BbCBM9_1 in ILB205 led to enhanced virulence against P. guildinii and Tenebrio molitor, as well as improved conidial germination, tolerance to oxidative and cell wall stress, and increased growth in nutrient-rich and glycerol-supplemented media. This demonstrates that the enhanced virulence observed in ILB308 grown on n-pentadecane can be replicated by overexpressing an associated gene in a low-virulence strain. Our study, highlights the potential of integrating transcriptomics and targeted genetic modifications to optimize fungal biocontrol agents for improved pest management.

microbiology↗

bioRxiv2024

Novel genomic features in entomopathogenic fungus Beauveria bassiana: supernumerary chromosomes and putative virulence genes involved in the infection process of soybean pest Piezodorus guildinii.

Biological control methods involving entomopathogenic fungi like Beauveria bassiana have shown to be a valuable approach in integrated pest management as an environmentally friendly alternative to control pests and pathogens. Identifying genetic determinants of pathogenicity in B. bassiana is instrumental for enhancing its virulence against insects like the resistant soybean pest Piezodorus guildinii. This study focused on comparative genomics of different B. bassiana strains and gene expression analyses to identify virulence genes in the hypervirulent strain ILB308, especially in response to infection of P. guildniii and growth on hydrocarbon HC15, a known virulence enhancer. Strain ILB308 showed the highest number of virulence-related features, such as candidate virulence proteins, effectors, small secreted proteins, and biosynthetic gene clusters. ILB308 also had a high percentage of unique DNA sequences, including six putative supernumerary scaffolds. Gene expression analysis at 4 days post-inoculation revealed upregulation of known virulence factors, including Tudor domain proteins, LysM motif-containing proteins, and subtilisin-like proteases, and novel genes like secreted effectors and heat-labile enterotoxins. Growth on HC15 led to the upregulation of genes associated with oxidoreductase activity related to cuticular alkane degradation and fermentation metabolism/antioxidant responses in the hemolymph. The presence of supernumerary chromosomes and unique virulence genes in ILB308 may contribute to its higher virulence and could be considered as potential targets for enhancing fungal virulence through genetic manipulation. Author SummaryUnderstanding mechanisms of virulence and virulence enhancement in Beauveria bassiana can lay the basis for the development of improved biocontrol agents. Here we used genomic and transcriptomic approaches to study the infection process of ILB308 -an hypervirulent strain- against insect pest Piezodorus guildinii. We found that this strain has putative supernumerary chromosomes and an enriched set of presumed virulence proteins like secreted effectors. We infer that the particular assortment of strain specific genes and supernumerary chromosome/s play a role in the degree of virulence exhibited by ILB308 and could be used for future strain improvement strategies.

genomics↗