Abstract
The haloacid dehalogenase (HAD) superfamily is one of the largest enzyme families, consisting mainly of phosphatases. Although intracellular phosphate plays important roles in many cellular activities, the biological functions of HAD enzymes are largely unknown. Pho13 is 1 of 16 putative HAD enzymes in Saccharomyces cerevisiae. Pho13 has not been studied extensively, but previous studies have identified PHO13 to be a deletion target for the generation of industrially attractive phenotypes, namely, efficient xylose fermentation and high tolerance to fermentation inhibitors. In order to understand the molecular mechanisms underlying the improved xylose-fermenting phenotype produced by deletion of PHO13 (pho13Δ), we investigated the response of S. cerevisiae to pho13Δ at the transcriptomic level when cells were grown on glucose or xylose. Transcriptome sequencing analysis revealed that pho13Δ resulted in upregulation of the pentose phosphate (PP) pathway and NADPH-producing enzymes when cells were grown on glucose or xylose. We also found that the transcriptional changes induced by pho13Δ required the transcription factor Stb5, which is activated specifically under NADPH-limiting conditions. Thus, pho13Δ resulted in the upregulation of the PP pathway and NADPH-producing enzymes as a part of an oxidative stress response mediated by activation of Stb5. Because the PP pathway is the primary pathway for xylose, its upregulation by pho13Δ might explain the improved xylose metabolism. These findings will be useful for understanding the biological function of S. cerevisiae Pho13 and the HAD superfamily enzymes and for developing S. cerevisiae strains with industrially attractive phenotypes.