Transcriptional profiling of carotenoid producing S. cerevisiae cells

To obtain insight in the genome-wide response of heterologous carotenoid production in Saccharomyces cerevisiae, we have analyzed the transcriptome of S. cerevisiae strains overexpressing carotenogenic genes from the yeast Xanthophyllomyces dendrorhous. For this purpose, two strains producing different levels of carotenoids were grown in carbon-limited continuous cultures and genome-wide expression was analyzed. The strain producing low carotenoid levels did not exhibit a clear genome-wide transcriptional response, suggesting that low carotenoid levels do not result in cellular stress. Transcriptome analysis of a strain producing high carotenoid levels resulted in specific induction of genes involved in pleiotropic drug resistance (PDR). These genes encode ATP-binding cassette (ABC) type transporters and major facilitator transporters which are involved in secretion of toxic compounds out of cells. Our results suggest that production of high amounts of carotenoids in S. cerevisiae lead to toxicity and that these cells are prone to secrete carotenoids out of the cell. Indeed, secretion of beta-carotene into sunflower oil was observed upon addition of this hydrophobic solvent to the growth medium. Finally, it was observed that deletion of the ABC transporter pdr10, one of the induced PDR transporters, highly decreased the transformation efficiency of an episomal vector containing carotenogenic genes. The few colored transformants that were obtained had decreased growth rates and lower carotenoid production levels compared to control strains transformed with the same carotenogenic genes. These results indicate that Pdr10 might be specifically involved in carotenoid tolerance in S. cerevisiae strains.

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Verwaal R, Jiang Y, Wang J, Daran JM, Sandmann G, van den Berg JA, van Ooyen AJ