Transcriptomic comparison of Aspergillus niger growing on two different sugars reveals coordinated regulation of the secretory pathway

Abstract

Background: The filamentous fungus, Aspergillus niger, responds to nutrient availability by modulating secretion of various substrate degrading hydrolases. This ability has made it an important organism in industrial production of secreted glycoproteins. The recent publication of the A. niger genome sequence and availability of microarrays allow high resolution studies of transcriptional regulation of basal cellular processes, like those of glycoprotein synthesis and secretion. It is known that the activities of certain secretory pathway enzymes involved Nglycosylation are elevated in response to carbon source induced secretion of the glycoprotein glucoamylase. We have investigated whether carbon source dependent enhancement of protein secretion can lead to upregulation of secretory pathway elements extending beyond those involved in N-glycosylation.

Integrated Approaches for Assessment of Cellular Performance in Industrially Relevant Filamentous Fungi

“…In a study to assess the physiological characterization of A. niger grown in chemostats with xylose or maltose as the limiting substrate and growth controlled at the same rate. 80 The data obtained included transcription profiles and an estimation of quantitative physiological parameters. The increased secretion potential on maltose was related to the induced transcription of more than 90 genes that regulate protein secretion, leading to the identification of putative regulatory elements and a greater understanding of the secretory pathway in filamentous fungi.…”

“…One example is a study on the effect of glucoamylase over-expression in maltose-limited chemostats through transcriptomics. 80 A notable finding was the identification of a set of only 40 differentially expressed core genes that ensure high protein traffic through the secretory pathway. In a study of T. reesei, gene expression was correlated to protein production rate in chemostat cultures at a range of specific growth rates.…”

“…These have been applied to study the transcriptional response of A. niger at growth rates approaching zero. 80 Related studies by the same group focused on carbon starvation and showed a correlation between transcriptomics analysis and the morphological development of the culture-leading to the proposition of a model for the carbon starvation response of A. niger.…”

Molecular genetic analysis of vesicular transport in Aspergillus niger reveals partial conservation of the molecular mechanism of exocytosis in fungi

“…Experiments in A. niger in chemostat cultures grown at identical growth rates on different carbon sources (xylose or maltose) revealed different protein production rates. The specific production rate of extracellular proteins on maltose was about three times higher than on xylose at identical growth rates (Jørgensen et al, 2009). One possible mechanism to explain this uncoupling of growth and secretion in A. niger would be the existence of two parallel secretory pathways that independently deliver proteins destined for secretion (e.g.…”

Construction of an Engineering Strain Producing High Yields of α-TransglucosidaseviaAgrobacterium tumefaciens-Mediated Transformation ofAsperillus niger

“…Owing to its high secretion capacity and being generally regarded as safe (GRAS) status, A. niger has been in use for many decades to produce a large number of enzymes (e.g., -transglucosidase, glucoamylase) 1) and organic acids (e.g., citric acid). 2,3) The long history of using A. niger on an industrial scale makes it well developed as a transformation host to overexpress foreign proteins. In recent years, a number of genes have been cloned and expressed in the A. niger expression system.…”