白麴菌(Saccharomycopsis fibuligera)SNF4基因之功能性探討

Abstract

Glucose repression occurs widely in fungi and bacteria. When glucose is present in the medium, the genes required for the utilization of alternative carbon sources are repressed, transcribed at low level or not at all. In yeast Saccharomyces cerevisiae, Snf4p is required for derepression of glucose-suppress genes in response to glucose depletion. Previous studies suggested that glucose repression is also present in yeast Saccharomycopsis fibuligera which has many applications in industries. By 454 sequencing and sequence similarity analysis, we identify a putative SNF4 gene of S. fibuligera, sfSNF4 which has 66% nucleotide sequence identities with S. cerevisiae SNF4. To understand the functional similarity of S. cerevisiae SNF4 and S. fibuligera SNF4, we use two-step swapping procedures to replace S. cerevisiae SNF4 gene with sfSNF4. We obtained 3 independent S. cerevisiae SNF4Δ:: sfSNF4 clones which the SNF4 gene was replaced by sfSNF4. However, the replacement of S. cerevisiae SNF4 with sfSNF4 dose not rescue the genetic defect of losing the SNF4 gene in S. cerevisiae for not been able to grow with non-fermentable carbon source. Interestingly, cells of S. cerevisiae SNF4Δ:: sfSNF4 grow poorly in glucose containing nutrient media (YPD) compare to wild type S. cerevisiae and shows obvious growth defect compare to wild type S. cerevisiae and S. cerevisiae SNF4Δ. We believe that the expression of sfSNF4 gene may interfere with the glucose metabolism of S. cerevisiae by disrupting the expression regulation of glucose repression. Our results suggest that there might be functional differences between S. cerevisiae SNF4 and S. fibuligera SNF4.