Deletion of the col-26 Transcription Factor Gene and a Point Mutation in the exo-1 F-Box Protein Gene Confer Sorbose Resistance in Neurospora crassa .

L-Sorbose induces hyperbranching of hyphae, which results in colonial growth in The gene, which encodes a glucose sensor that acts in carbon catabolite repression (CCR), has been identified as a sorbose resistance gene. In this study, we found that the deletion mutant of , which encodes an AmyR-like transcription factor that acts in CCR, displayed sorbose resistance. In contrast, the deletion mutants of other CCR genes, such as a hexokinase (), an AMP-activated S/T protein kinase (), and a transcription factor (), showed no sorbose resistance. Double mutant analysis revealed that the deletion of , , and did not affect the sorbose resistance of the mutant. Genes for a glucoamylase (), an invertase (), and glucose transporters ( and ) were highly expressed in the mutant, even in glucose-rich conditions, but this upregulation was suppressed in the Δ;Δ double-deletion mutant. Furthermore, we found that a (L1) mutant with a single amino-acid substitution, S11L, in the F-box protein EXO-1 displayed sorbose resistance, unlike the deletion mutants of , suggesting that the function of EXO-1 is crucial for the resistance. Our data strongly suggest that CCR directly participates in sorbose resistance, and that COL-26 and EXO-1 play important roles in regulating the amylase and glucose transporter genes during CCR.