科研之友
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摘要
Aspergillus niger is an important organism for the production of industrial enzymes such as hemicellulases and pectinases. The xylan-backbone monomer, D-xylose, is an inducing substance for the coordinate expression of a large number of polysaccharide-degrading enzymes. In this study, the responses of 22 genes to low (1 mM) and high (50 mM) D-xylose concentrations were investigated. These 22 genes encode enzymes that function as xylan backbone-degrading enzymes, accessory enzymes, cellulose-degrading enzymes, or enzymes involved in the pentose catabolic pathway in A. niger. Notably, genes encoding enzymes that have a similar e. g., xylan backbone degradation) respond in a similar manner to different concentrations of D-xylose. Although low D-xylose concentrations provoke the greatest change in transcript levels, in particular, for hemicellulase-encoding genes, transcript formation in the presence of high concentrations of D-xylose was also observed. Interestingly, a high D-xylose concentration is favorable for certain groups of genes. Furthermore, the repressing influence of CreA on the transcription and transcript levels of a subset of these genes was observed regardless of whether a low or high concentration of D-xylose was used. Interestingly, the decrease in transcript levels of certain genes on high D-xylose concentrations is not reflected by the transcript level of their activator, XlnR. Regardless of the D-xylose concentration applied and whether CreA was functional, xlnR was constitutively expressed at a low level.
- 出版日期2012-5
