Common features and interesting differences in transcriptional responses to secretion stress in the fungi Trichoderma reesei and Saccharomyces cerevisiae.
BACKGROUND
Secretion stress is caused by compromised folding, modification or transport of proteins in the secretory pathway. In fungi, induction of genes in response to secretion stress is mediated mainly by the unfolded protein response (UPR) pathway. This study aims at uncovering transcriptional responses occurring in the filamentous fungi Trichoderma reesei exposed to secretion stress and comparing these to those found in the yeast Saccharomyces cerevisiae.


RESULTS
Chemostat cultures of T. reesei expressing human tissue plasminogen activator (tPA) and batch bioreactor cultures treated with dithiothreitol (DTT) to prevent correct protein folding were analysed with cDNA subtraction and cDNA-amplified fragment length polymorphism (AFLP) experiments. ESTs corresponding to 457 unique genes putatively induced under secretion stress were isolated and the expression pattern of 60 genes was confirmed by Northern analysis. Expression of these genes was also studied in a strain over-expressing inositol-requiring enzyme 1 (IREI) protein, a sensor for the UPR pathway. To compare the data with that of S. cerevisiae, published transcriptome profiling data on various stress responses in S. cerevisiae was reanalysed. The genes up-regulated in response to secretion stress included a large number of secretion related genes in both organisms. In addition, analysis of T. reesei revealed up regulation of the cpc1 transcription factor gene and nucleosomal genes. The induction of the cpcA and histone gene H4 were shown to be induced also in cultures of Aspergillus nidulans treated with DTT.


CONCLUSIONS
Analysis of the genes induced under secretion stress has revealed novel features in the stress response in T. reesei and in filamentous fungi. We have demonstrated that in addition to the previously rather well characterised induction of genes for many ER proteins or secretion related proteins also other types of responses exist.
Arvas
Mikko
M
VTT Biotechnology, Tietotie 2, Espoo, PL 1500, 02044 VTT, Finland. mikko.arvas@vtt.fi
Pakula
Tiina
T
Lanthaler
Karin
K
Saloheimo
Markku
M
Valkonen
Mari
M
Suortti
Tapani
T
Robson
Geoff
G
Penttilä
Merja
M
D000596:Amino Acids / Q000096:biosynthesis; D050976:Basic-Leucine Zipper Transcription Factors; D015152:Blotting, Northern; D019295:Computational Biology; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics; D020224:Expressed Sequence Tags; D005656:Fungal Proteins / Q000096:biosynthesis / Q000235:genetics; D015966:Gene Expression Regulation, Fungal; D015723:Gene Library; D023281:Genomics; D006657:Histones / Q000096:biosynthesis / Q000235:genetics; D011110:Polymorphism, Genetic; D017510:Protein Folding; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000096:biosynthesis / Q000235:genetics; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics; D014158:Transcription, Genetic; D014242:Trichoderma / Q000235:genetics* / Q000378:metabolism
D000596:Amino Acids; D050976:Basic-Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C501391:GCN4 protein, S cerevisiae; D006657:Histones; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors