| Summary: | <p>Abstract</p> <p>Background</p> <p><it>Pichia pastoris </it>is a well established yeast host for heterologous protein expression, however, the physiological and genetic information about this yeast remains scanty. The lack of a published genome sequence renders DNA arrays unavailable, thereby hampering more global investigations of <it>P. pastoris </it>from the beginning. Here, we examine the suitability of <it>Saccharomyces cerevisiae </it>DNA microarrays for heterologous hybridisation with <it>P. pastoris </it>cDNA.</p> <p>Results</p> <p>We could show that it is possible to obtain new and valuable information about transcriptomic regulation in <it>P. pastoris </it>by probing <it>S. cerevisiae </it>DNA microarrays. The number of positive signals was about 66 % as compared to homologous <it>S. cerevisiae </it>hybridisation, and both the signal intensities and gene regulations correlated with high significance between data obtained from <it>P. pastoris </it>and <it>S. cerevisiae </it>samples. The differential gene expression patterns upon shift from glycerol to methanol as carbon source were investigated in more detail. Downregulation of TCA cycle genes and a decrease of genes related to ribonucleotide and ribosome synthesis were among the major effects identified.</p> <p>Conclusions</p> <p>We could successfully demonstrate that heterologous microarray hybridisations allow deep insights into the transcriptomic regulation processes of <it>P. pastoris</it>. The observed downregulation of TCA cycle and ribosomal synthesis genes correlates to a significantly lower specific growth rate during the methanol feed phase.</p>
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