Upregulation of genes involved in gluconeogenesis and the glyoxylate cycle suppressed the drug sensitivity of an N-glycan-deficient Saccharomyces cerevisiae mutant.

Saccharomyces cerevisiae strain TIY20, which produces a mammalian high-mannose type N-glycan, exhibits a severe growth defect due to disruption of yeast-specific outer chain mannosyltransferases. We have isolated a more fit strain, YAB103, from TIY20 by the use of a novel mutagenesis technique based on the disparity theory of evolution. To determine why YAB103 lacked the growth defect and the hygromycin B sensitivity of its parent, TIY20, gene expression profiles of YAB103 and TIY20 were analyzed using DNA microarrays. Expression of genes that encode enzymes in the gluconeogenesis pathway and glyoxylate cycle, which produce glucose 6-phophate and its derivatives, was up-regulated in YAB103. Up-regulation of these genes suppressed the drug sensitivity of the TIY20 strain. Furthermore, we found that YAB103 had a thicker cell-wall due to an increase in glucan content. To our knowledge, this is first report linking N-glycosylation to gluconeogenesis and the glyoxylate cycle.