3.5. Transcriptional changes in central metabolic pathways induced by gcr2
To better understand the effect of gcr2 on xylose metabolism, the fold changes of DE genes in the glycolytic pathway, the PPP, and the citric acid cycle were systematically compared between glucose and xylose conditions (Fig. 4). Two significant transcriptional changes were observed on both glucose and xylose conditions. First, gcr2 led to the down-regulation of some glycolytic genes, most critically theGPM1 gene, encoding phosphoglycerate mutase, which is a key enzyme of the lower glycolic pathway. Second, gcr2 up-regulated non-oxidative PPP genes, most critically the TAL1 gene, encoding transaldolase. However, in greater detail, gcr2 -mediated transcriptional changes in central metabolic pathways were more prominent during xylose metabolism. In addition to GPM1 gene,TDH2 , ENO1 , and CDC19 genes in the lower glycolytic pathway were significantly down-regulated only under xylose conditions. Moreover, SOL4 , GND2 , and TKL2 genes in oxidative and non-oxidative PPP were up-regulated considerably only under xylose conditions.