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