Transcriptional responses of yeast to preferred and non-preferred nitrogen sources in C-lim chemostat cultures

Aerobic, glucose-limited chemostat cultures of Saccharomyces cerevisiae grown with six different nitrogen sources were subjected to transcriptome analysis. The use of chemostats enabled an analysis of nitrogen-source-dependent transcriptional regulation at a fixed specific growth rate. A selection of preferred (ammonium and asparagine) and non-preferred (leucine, phenylalanine, methionine and proline) nitrogen sources was investigated. For each nitrogen source, distinct sets of genes were induced or repressed relative to the other five nitrogen sources. A total number of 131 of such signature transcripts were identified in this study. In addition to signature transcripts, genes were identified that showed a transcriptional co-response to two or more of the six nitrogen sources. For example, 33 genes were transcriptionally up-regulated in leucine-, phenylalanine- and methionine-grown cultures, which was partly attributed to the involvement of common enzymes in the dissimilation of these amino acids. In addition to specific transcriptional responses elicited by individual nitrogen sources, their impact on global regulatory mechanisms such as nitrogen catabolite repression (NCR) could be monitored. NCR-sensitive gene expression in the chemostat cultures showed that, ammonia and asparagine were rich nitrogen sources. By this criterion, leucine, proline and methionine were poor nitrogen sources and phenylalanine showed an intermediate NCR response.

15

Boer VM, Tai SL, Vuralhan Z, Arifin Y, Walsh MC, Piper MD, de Winde JH, Pronk JT, Daran JM