Transcription factor BbCDR1 regulates the orchestration between conidial formation and maturation in the entomopathogenic fungus Beauveria bassiana.

Background: The entomopathogenic fungus Beauveria bassiana has been widely used for pest biocontrol with conidia serving as the main active agents. Conidial yield and quality are two important characteristics in fungal conidia development, however, the regulatory mechanisms that orchestrate conidial formation and development are not well understood.

Results: In this study, we identified a ZnCys transcription factor BbCDR1 that inhibits conidial production while promoting conidial maturation. Compared with the wild type, the ΔBbCDR1 mutant exhibited a 1.88-fold increase in conidial yield but a reduction in conidial quality, including decreased cell wall integrity and trehalose synthesis. The deletion of BbCDR1 also led to reduced conidial germination rates under oxidative, osmotic, conidial wall disruption and UV stresses. Interestingly, ΔBbCDR1 exhibited an increase of fungal virulence with a 12.5% decrease in LT compared to the wild type.

Conclusions: Further analysis revealed that BbCDR1 represses the expression of BbbrlA and activates BbwetA, two components of the central developmental pathway (CDP) that regulate conidial initiation and maturation, respectively. These findings suggest that BbCDR1 plays a crucial role in conidial development and a new target gene for the genetic engineering of highly active fungal insecticides. © 2025 Society of Chemical Industry.