d -Xylose Concentration-Dependent Hydrolase Expression Profiles and the Function of CreA and XlnR in Aspergillus niger

Abstract

<jats:title>ABSTRACT</jats:title><jats:p><jats:named-content content-type="genus-species">Aspergillus niger</jats:named-content>is an important organism for the production of industrial enzymes such as hemicellulases and pectinases. The xylan-backbone monomer,<jats:sc>d</jats:sc>-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)<jats:sc>d</jats:sc>-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<jats:named-content content-type="genus-species">A. niger</jats:named-content>. Notably, genes encoding enzymes that have a similar function (e.g., xylan backbone degradation) respond in a similar manner to different concentrations of<jats:sc>d</jats:sc>-xylose. Although low<jats:sc>d</jats:sc>-xylose concentrations provoke the greatest change in transcript levels, in particular, for hemicellulase-encoding genes, transcript formation in the presence of high concentrations of<jats:sc>d</jats:sc>-xylose was also observed. Interestingly, a high<jats:sc>d</jats:sc>-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<jats:sc>d</jats:sc>-xylose was used. Interestingly, the decrease in transcript levels of certain genes on high<jats:sc>d</jats:sc>-xylose concentrations is not reflected by the transcript level of their activator, XlnR. Regardless of the<jats:sc>d</jats:sc>-xylose concentration applied and whether CreA was functional,<jats:italic>xlnR</jats:italic>was constitutively expressed at a low level.</jats:p>

Xylanase Gene Transcription in Trichoderma reesei Is Triggered by Different Inducers Representing Different Hemicellulosic Pentose Polymers

“…xyn1 and xyn2 were previously reported to be subject to regulation by the C 2 H 2 carbon catabolite repressor CRE1 via a doublelock mechanism (19,38) that controls xylanase transcription at two different levels, by direct repression through CRE1, and indirectly through the CRE1-mediated repression of the transcriptional activator XYR1 (39). Binding sites for the carbon catabolite repressor CRE1 are present in all xylanase genes ( Fig.…”

Transcriptional Regulation and Responses in Filamentous Fungi Exposed to Lignocellulose

“…Other reviews also summarises some of the relevant inducers and induction mechanisms [13,29]. In A. niger, xylose (a sugar that forms the backbone of xylan and is found in other hemicelluloses and pectins) induces cellulase as well as hemicellulase-encoding genes [50]. The effect of this molecule is concentration dependent where higher xylose concentrations can be repressive in a CreA-dependent manner, rather than inductive [51].…”

Organic acid production in Aspergillus niger and other filamentous fungi

“…µL) contained 7.5 µL of 2x ABsolute QPCR SYBR Green mix, 100 nM forward and reverse primers and 2.5 µL cDNA (diluted 1:100). The primers used for qPCR analysis were designed using the software QuantPrime (Arvidsson et al, 2008), and are listed in S2 were used as reference for normalization of the expression data (Mach-Aigner et al, 2012;van der Veen et al, 2009). Dissociation (or melting) curve analysis was performed on each qPCR reaction to confirm that the primer pairs used produced a single amplification product.…”

“…Reverse transcription, quantitative PCRs and calculations were performed following the protocols and instruments described in Mach-Aigner et al, 2012(Mach-Aigner et al, 2012. Primer sequences are provided in Additional file 9.…”