Adaptation of <it>Hansenula polymorpha </it>to methanol: a transcriptome analysis

• Main Authors: Kuipers Oscar P, de Jong Anne, Susanna Kim A, Baerends Richard JS, van Zutphen Tim, Veenhuis Marten, van der Klei Ida J
• Format: Article
• Language: English
• Published: BMC 2010-01-01
• Series: BMC Genomics
• Online Access: http://www.biomedcentral.com/1471-2164/11/1

<p>Abstract</p> <p>Background</p> <p>Methylotrophic yeast species (e.g. <it>Hansenula polymorpha, Pichia pastoris</it>) can grow on methanol as sole source of carbon and energy. These organisms are important cell factories for the production of recombinant proteins, but are also used in fundamental research as model organisms to study peroxisome biology. During exponential growth on glucose, cells of <it>H. polymorpha </it>typically contain a single, small peroxisome that is redundant for growth while on methanol multiple, enlarged peroxisomes are present. These organelles are crucial to support growth on methanol, as they contain key enzymes of methanol metabolism.</p> <p>In this study, changes in the transcriptional profiles during adaptation of <it>H. polymorpha </it>cells from glucose- to methanol-containing media were investigated using DNA-microarray analyses.</p> <p>Results</p> <p>Two hours after the shift of cells from glucose to methanol nearly 20% (1184 genes) of the approximately 6000 annotated <it>H. polymorpha </it>genes were significantly upregulated with at least a two-fold differential expression. Highest upregulation (> 300-fold) was observed for the genes encoding the transcription factor Mpp1 and formate dehydrogenase, an enzyme of the methanol dissimilation pathway. Upregulated genes also included genes encoding other enzymes of methanol metabolism as well as of peroxisomal β-oxidation.</p> <p>A moderate increase in transcriptional levels (up to 4-fold) was observed for several <it>PEX </it>genes, which are involved in peroxisome biogenesis. Only <it>PEX11 </it>and <it>PEX32 </it>were higher upregulated. In addition, an increase was observed in expression of the several <it>ATG </it>genes, which encode proteins involved in autophagy and autophagy processes. The strongest upregulation was observed for <it>ATG8 </it>and <it>ATG11</it>.</p> <p>Approximately 20% (1246 genes) of the genes were downregulated. These included glycolytic genes as well as genes involved in transcription and translation.</p> <p>Conclusion</p> <p>Transcriptional profiling of <it>H. polymorpha </it>cells shifted from glucose to methanol showed the expected downregulation of glycolytic genes together with upregulation of the methanol utilisation pathway. This serves as a confirmation and validation of the array data obtained. Consistent with this, also various <it>PEX </it>genes were upregulated. The strong upregulation of <it>ATG </it>genes is possibly due to induction of autophagy processes related to remodeling of the cell architecture required to support growth on methanol. These processes may also be responsible for the enhanced peroxisomal β-oxidation, as autophagy leads to recycling of membrane lipids. The prominent downregulation of transcription and translation may be explained by the reduced growth rate on methanol (t_dglucose 1 h vs t_dmethanol 4.5 h).</p>