Abstract
ABSTRACTDuring induced differentiation, the process often involves a commitment event, after which induced cells, when returned to noninducing conditions, continue to differentiate. The commitment event is rarely identified. Candida albicans differentiates from the white to opaque phenotype, a prerequisite for mating and a process accompanying colonization of the lower gastrointestinal tract and skin. In analyses of white cell populations induced to synchronously differentiate from the white to opaque phenotype, opaque commitment occurs at approximately the same time as evagination and chitin ring formation in the process of daughter cell formation, several hours after the master switch gene WOR1 is upregulated. Mutational analyses of transcription factor binding regions P1, P2, P3, P4, and P6 of the WOR1 promoter reveal that individual deletion of any of the five transcription factor binding regions does not eliminate morphological differentiation to the opaque cell phenotype under opaque-inducing conditions, but individual deletion of P2, P3, or P4, blocks opaque commitment and maintenance of the opaque phenotype after transition to noninducing conditions. These results suggest that commitment occurs at the level of the WOR1 promoter and that morphological differentiation can be dissociated from phenotypic commitment.
Highlights
During induced differentiation, the process often involves a commitment event, after which induced cells, when returned to noninducing conditions, continue to differentiate
We mean the time after which opaque-induced white cells, when replated under noninducing conditions, continue to transition to and maintain the opaque phenotype
The results show that opaque commitment occurs at the time induced cells evaginate and form a chitin ring at the mother cell-bud junction, several hours after upregulation of the TF WOR1, which encodes a transcription factor essential for switching
Summary
The process often involves a commitment event, after which induced cells, when returned to noninducing conditions, continue to differentiate. Mutational analyses of transcription factor binding regions P1, P2, P3, P4, and P6 of the WOR1 promoter reveal that individual deletion of any of the five transcription factor binding regions does not eliminate morphological differentiation to the opaque cell phenotype under opaque-inducing conditions, but individual deletion of P2, P3, or P4, blocks opaque commitment and maintenance of the opaque phenotype after transition to noninducing conditions These results suggest that commitment occurs at the level of the WOR1 promoter and that morphological differentiation can be dissociated from phenotypic commitment. By analyzing deletion derivatives of the WOR1 promoter, we demonstrate that three of five regulatory regions of WOR1 that bind TFs involved with the regulation of the phenotypic switch are individually required for commitment to the opaque phenotype, but are not necessary for expressing the opaque phenotype These results demonstrate that morphological differentiation can be dissociated from phenotypic commitment and that commitment occurs at the level of the WOR1 promoter. We demonstrate that cells lacking any one of three TF binding regions can express the opaque cell phenotype under inducing conditions, but cannot commit to the opaque phenotype, demonstrating that expression of the opaque phenotype can be dissociated from commitment to the opaque phenotype
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