# Essential role of sugar transporters BbStp13 in fungal virulence, conidiation, and cell wall integrity in entomopathogenic fungus Beauveria bassiana

## TL;DR

This study shows that the sugar transporter BbStp13 is crucial for the fungus Beauveria bassiana to infect insects, produce spores, and maintain cell wall strength.

## Contribution

The study identifies BbStp13 as a novel sugar transporter essential for fungal virulence and development in Beauveria bassiana.

## Key findings

- Deletion of BbStp13 reduces the fungus's ability to infect insect cuticles.
- BbStp13 is vital for conidia production, especially under low sugar conditions.
- BbStp13 helps maintain cell wall integrity and evade host immune responses.

## Abstract

Fungi primarily utilize sugar as energy sources, with their uptake facilitated by sugar transporters. Beauveria bassiana is an entomopathogenic fungus widely applied in pest biological control. This study identified 43 sugar transporter proteins in B. bassiana, of which 27 exhibited higher expression in aerial mycelia, indicating a greater reliance on sugar transport during aerial development. Notably, one transporter, BbStp13, demonstrated significantly elevated expression in aerial mycelia. Using homologous replacement and ectopic insertion techniques, BbStp13 deletion and complementation strains were constructed. The deletion of BbStp13 resulted in reduced virulence of B. bassiana, particularly during cuticle infection. Sugar transporters are also crucial for conidia development, a process essential for fungal dispersal. Deletion of BbStp13 impaired conidia production, especially under sugar-limited conditions. Furthermore, BbStp13 proteins mediate host–fungus interactions by modifying carbohydrate profiles on the fungal cell surface, thus influencing host immune recognition. Additionally, the BbStp13 protein is vital for maintaining cell wall homeostasis, contributing to the fungus’s resistance to host hemocoel stresses. In conclusion, the sugar transporter BbStp13 is central to maintaining fungal virulence, conidia development, cell wall integrity, and immune evasion during infection. This study broadens our understanding of sugar transporters in fungal physiology and provides deeper insights into the mechanisms underlying the lifestyle of entomopathogenic fungi. Furthermore, these findings identify potential targets for optimizing the efficacy of B. bassiana as a biological control agent, paving the way for more effective pest management strategies.