Carbon catabolite repressor gene BbCre1 influences carbon source uptake but does not have a big impact on virulence in Beauveria bassiana

A gene (BbCre1, GenBank accession number EF108309) encoding a carbon catabolite repressor (CreA) with two Cys2His2 zinc finger regions and a nuclear localization signal was cloned from the entomopathogenic fungus Beauveria bassiana. Overexpression and antisense strategies were used to investigate the biological functions of this gene. Compared with the wild type, the conidial yield and colony growth of BbCre1-overexpression transformants were significantly decreased on the plates with xylose or ethanol as the sole carbon source. With glucose as the sole carbon source, a significant difference was observed in the activity of Pr1A-like protease among BbCre1-overexpression transformants, antisense-BbCre1 transformants and the wild type. However, bioassays showed that knockdown or overexpression of BbCre1 did not have a significant impact on the virulence of B. bassiana to aphids. These results imply that the fungus remains virulent, even when simpler, less expensive nutrients are available, i.e. glucose.

Graphical abstractJournal of Invertebrate Pathology (JIP-10-122): Function of a gene encoding a carbon catabolite repressor, BbCre1, was analyzed using overexpression and antisense silencing strategies in Beauveria bassiana. With glucose as sole carbon source, the specific production rate of Pr1A-like protease of the antisense transformants was 1 to 2-fold increased for than that of the control strain during the exponential growth phase. Bioassays showed that antisense silencing or overexpression of BbCre1 did not have a significant impact on the virulence of B. bassiana to aphids. The results implicate that the fungus remains virulent even when the cheaper of nutrients, i.e. glucose, is available.Download full-size imageResearch highlights► BbCre1 encoding a carbon catabolite repressor is cloned from Beauveria bassiana. ► BbCre1 is regulated by glucose and involved in the carbon source uptake. ► BbCre1 affects the fungal Pr1A-like protease activity with glucose as carbon source. ► BbCre1 does not have a significant impact on the virulence of B. bassiana to aphids. ► Fungus remains virulent even when cheaper of nutrients, i.e. glucose, are available.