The filamentous fungus Aspergillus niger is well known for its exceptional high capacity to secrete proteins. However, system-wide insights into its secretory capacities are sparse and rational strain improvement approaches are thus limited. To gain a global view on the transcriptional basis of the secretory pathway of A. niger, we have investigated its transcriptomic fingerprint when specifically forced to overexpress the hydrolytic enzyme glucoamylase (GLA). An A. niger wild-type strain and an GLA over-expressing strain where cultivated under maltose-limited chemostat conditions. Elevated glaA mRNA and extracellular GLA levels in the over-expressing strain were accompanied by reinforced transcription of 772 genes and down-regulation of 815 genes when compared to the wild-type situation. Using GO term enrichment analysis, four higher order categories were identified in the up-regulated gene set: i) translocation, ii) protein glycosylation, iii) vesicle transport and iv) ion homeostasis. Among these, about 130 genes have predicted functions for the protein passage through the endoplasmaticum reticulum including well-known target genes of the HacA transcription factor, e.g. bipA, clxA, prpA, tigA and pdiA. To identify those genes, which are generally important for high-level secretion in A. niger, we compared the GLA transcriptome with six other secretion stress transcriptomes of A. niger, including a constitutive active HacA transcriptome, several UPR stress transcriptomes and a carbonsource induced secretion transcriptome. Overall, 40 genes were commonly up-/down-regulated under these three conditions (36 genes up-regulated, 4 down-regulated), thus defining the core set of genes important for ensuring high protein traffic through the secretory pathway.
Full conference title:
27th Fungal Genetics Conference
- Fungal Genetics Conference 27th (2013)