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Dissecting the complex regulation of pentose utilization in Aspergillus niger

Summary

This research identifies how the fungus Aspergillus niger recognizes and responds to different types of sugars found in plant cell walls. Scientists discovered that the fungus uses two control proteins (AraR and XlnR) that are activated by specific sugar molecules: L-arabitol for AraR and D-xylose for XlnR. Importantly, the fungus can distinguish between left and right-handed versions of these sugars, showing remarkable chemical specificity. This understanding is important for biotechnology applications including biofuel and biochemical production.

Background

L-arabinose and D-xylose are major components of plant cell wall polysaccharides and important carbon sources for microorganisms. Fungi convert these pentose sugars through the pentose catabolic pathway (PCP), which is controlled by two transcriptional activators, XlnR and AraR. While it is known that XlnR is active during growth on D-xylose and AraR on L-arabinose, the actual monomeric inducers of these regulators have not been definitively established.

Objective

This study aimed to identify the specific monomeric inducers of the transcriptional regulators AraR and XlnR in Aspergillus niger through comparative transcriptomics and metabolic analysis of PCP intermediates and their chiral counterparts.

Results

L-arabitol was identified as the monomeric inducer of AraR, while D-xylose was identified as the inducer of XlnR. The induction of both regulators was shown to be chiral-specific, with L-xylose and D-arabinose failing to induce their respective regulators. Metabolic mutants revealed complex regulation and suggested additional pathways for sugar conversion.

Conclusion

This comprehensive study definitively established that L-arabitol and D-xylose are the specific monomeric inducers of AraR and XlnR respectively in A. niger, and demonstrated that this induction is chiral-sensitive. These findings provide important insights into the complex regulation of fungal pentose utilization relevant for biotechnological applications.
  • Published in:Current Research in Microbial Science,
  • Study Type:Experimental Study,
  • Source: 10.1016/j.crmicr.2025.100482, PMID: 41127560
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