Transcriptional and metagenomic changes in soybean plants carrying fungus Beauveria bassiana

Entomopathogenic fungi, such as Beauveria bassiana, have been naturally isolated from various plant species and have also been introduced as endophytes to enhance plant health and resilience. These fungal endophytes are often associated with improved plant defense against insect pest herbivory. This study aimed to assess the endophytic capacity of B. bassiana ARSEF 2860 in soybean plants and to investigate the associated changes in gene expression and leaf microbiome composition one-week post-inoculation. Results demonstrated that B. bassiana successfully colonized the leaves, stems, and roots of soybean plants and induced significant alterations in both gene expression and microbial communities in leaves. Specifically, the fungal endophyte down-regulated genes related to responses to far-red light and the abscisic acid pathway, while up-regulating genes involved in photosynthesis, lipid and carbohydrate biosynthesis, and stress response. Additionally, the fungal inoculation reduced the total microbial reads in leaves, with a decrease in pathogenic bacterial species and an increase in probiotic bacterial species. Total fungal reads were also lower in B. bassiana-colonized plants compared to control samples, with plant-pathogenic fungal reads being reduced. These findings highlight the role of entomopathogenic fungal endophytes to promote plant growth by potentially enhancing photosynthesis, strengthening plant defense mechanisms, and suppressing plant pathogenic microbes.