Oral Presentation 2-05

Genome-wide Transcriptional Analysis of

Xylose-growing Saccharomyces cerevisiae Strains

Marie Jeppsson,¹ Marco Sonderegger,² Uwe Sauer,² César Fonseca,³ Sofia Santos,³

Isabel Spencer-Martins,³ Bärbel Hahn-Hägerdal¹ and Marie F. Gorwa-Grauslund¹*

¹Department of Applied Microbiology

Lund University

PO Box 124

SE-221 00 Lund, Sweden

Phone: 46 46 222 0619

Fax: 46 46 222 4203

E-mail: Marie-Francoise.gorwa@tmb.lth.se

²Institute of Biotechnology, ETH Zürich, CH-8093 Zürich, Switzerland.

³Centro de Recursos Microbiologicos (CREM), Faculty of Sciences and Technology

New University of Lisbon

2829-516, Caparica, Portugal

Xylose utilisation by baker's yeast Saccharomyces cerevisiae has been made possible with the integration of the Pichia stipitis XYL1 (encoding xylose reductase) and XYL2 (encoding xylitol dehydrogenase) genes and the overexpression of the endogenous XKS1 gene (encoding xylulokinase), however the constructed strains display a low growth rate on xylose. The subsequent use of chemical mutagenesis, selection and/or breeding has led to the generation of S. cerevisiae strains with enhanced xylose growth. In the present investigation, genome-wide transcription analysis was applied to pinpoint the genetic changes responsible for the xylose-growing phenotype in these strains.

Strains with enhanced xylose growth were compared to control strains using data generated from Yeast Genome S98 Arrays processed in MicroArray Suite 5.0 (Affymetrix). Several data sets were compared simultaneously to identify altered expression levels shared by part or all the xylose-growing strains. Limitations in xylose utilisation have previously been attributed to low expression of genes in the pentose phosphate pathway and in sugar transport. The mRNA expression levels of genes in central metabolism and in hexose transport were therefore compared separately. The expression level of transcriptional regulators was also investigated. Results from the transcription analysis will be presented.