Proteome and transcriptome analysis of the cellular responses to production of the heterologous protein, <i>Melanocarpus albomyces</i> laccase, in the filamentous fungus <i>Trichoderma reesei</i>

Trichoderma reesei Rut-C30 and its transformant producing Melanocarpusalbomyces laccase were cultivated in lactose-containing minimal medium inchemostats and subjected to proteome and transcriptome analysis to identifydifferentially expressed genes under these conditions. The cultures were carriedout using a dilution rate (0.03/h) previously shown to be optimal for productionof endogenous extracellular proteins under these conditions. The TRAC methodfor multiplexed transcriptional analysis was first applied to analyse theexpression levels of a selected set of genes and to monitor the steady state inthe chemostat cultures. The results indicated that UPR (unfolded proteinresponse) pathway was not activated as a response to laccase production. Onthe contrary, the expression levels of e.g. the foldase and chaperone genes pdi1and bip1 were expressed at a slightly higher level in the host. Also theexpression levels of the genes encoding the endogenous secreted cellulases,egl1 and cbh1, were slightly higher in the host strain. Both proteome andgenome wide transcriptional analysis using oligonucleotide microarrays revealedonly a modest number of cellular responses to laccase production. Altogether 32genes were differentially expressed between the strains, only five of the genesbeing upregulated in the laccase producing strain, and the rest having a higherexpression level in the host strain and including many genes encodingextracellular enzymes. Proteome analysis using 2D gel electrophoresis with DIGEshowed increased expression of a group of proteins including e.g. heat shockproteins as well ubiquitin associated proteins and proteins involved in ERassociated protein degradation. The result indicates that although laccaseexpression does not induce apparent UPR, other type stress responses areinduced e.g. activated protein degradation. The results were also compared tothose obtained in previous studies on the production human tissue plasminogenactivator (tPA) in T. reesei