Transcriptome analysis of xylose metabolism in the thermotolerant methylotrophic yeast Hansenula polymorpha

Abstract

The thermotolerant methylotrophic yeast Hansenula polymorpha is able to grow at elevated temperature up to 48 °C as one of a few yeast strains which are naturally capable of alcoholic fermentation of xylose, a pentose sugar abundant in lignocellulosic biomass. However, the current level of ethanol production from xylose by H. polymorpha is still very low compared to those of other xylose-fermenting strains. Therefore, it is necessary to analyze and remodel the xylose metabolism in H. polymorpha at the whole genome level to identify and overcome these limits. In the present study, the transcriptomes of H. polymorpha grown on xylose were compared with those of glucose-grown cells under both aerobic and microaerobic conditions. Approximately, two percent of H. polymorpha genes were either up- or down-regulated by more than two-fold during the growth on xylose. The majority of the up-regulated genes were involved in metabolism. Some genes involved in xylose metabolism, such as XYL1, XYL2, and TAL1 were also up-regulated, despite the fact that the differences in their induction level were only about three-fold. On the other hand, the majority of the down-regulated genes were involved in metabolism and cellular transport. Interestingly, some genes involved in glycolysis and ethanol fermentation were also repressed during growth on xylose, suggesting that these genes are good targets for engineering H. polymorpha to improve xylose fermentation.

Proteome analysis of xylose metabolism in Rhodotorula toruloides during lipid production

“…Additional metabolic processes displaying significant changes in protein levels between glucose- and xylose-grown R. toruloides cells included biosynthesis of amino acids and phospholipids as well as oxidative stress response. Similar effect of xylose on ethanol-producing yeasts has been reported previously [44–46]. Some of these effects, such as downregulation of leucine biosynthesis and upregulation of xylose transporters during growth on xylose were reminiscent of proteomic changes observed in ethanol-producing yeasts during cultivation on either xylose or glucose.…”

“…A number of previous proteomic and transcriptomic studies have investigated metabolism of xylose in ethanol-producing yeasts [44–46], while this study of R. toruloides represents the first proteomic investigation of an oleaginous yeast during conversion of xylose to lipids. As the major constituent of hemicellulose, xylose is the second-most abundant monosaccharide in nature after glucose [4].…”

“…While xylose utilization by oleaginous yeasts is poorly understood, a number of studies have investigated xylose metabolism in ethanol-producing yeasts: e.g. in engineered Saccharomyces cerevisiae [44], Schefferomyces stipitis [45], and Ogataea polymorpha [46]. These studies reported that the carbon source affected levels of proteins involved in e.g.…”

Transcriptional activator Cat8 is involved in regulation of xylose alcoholic fermentation in the thermotolerant yeast Ogataea (Hansenula) polymorpha

“…Role of CAT8 in regulation of xylose metabolism is poorly understood. Transcriptome analysis of the natural xylose-metabolizing yeast O. polymorpha did not find changes in CAT8 expression between xylose- and glucose-containing media [ 26 ]. In recombinant S. cerevisiae capable of xylose metabolism, xylose caused only weak repression of CAT8 relative to glucose suggesting xylose growing cells are in between totally repressed and derepressed state regarding catabolite repression [ 27 ].…”

Construction of advanced producers of first- and second-generation ethanol in Saccharomyces cerevisiae and selected species of non-conventional yeasts (Scheffersomyces stipitis, Ogataea polymorpha)

“…The role of CAT8 in regulation of xylose metabolism was poorly understood. Transcriptome analysis of the natural xylose-metabolizing yeast O. polymorpha did not find changes in CAT8 expression between xylose-and glucosecontaining media [88].…”