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Kre6-dependent β-1,6-glucan biosynthesis only occurs in the conidium of Aspergillus fumigatus

Summary

Researchers discovered that a specific sugar compound called β-1,6-glucan is found in the spore-like reproductive structures (conidia) of the fungus Aspergillus fumigatus but not in its growing filaments (mycelium). Using advanced nuclear magnetic resonance technology, they identified the KRE6 gene as responsible for making this sugar and found that removing this gene makes the fungus more vulnerable to certain chemicals that damage fungal cell walls.

Background

The structural role of β-1,6-glucan has been under-investigated in filamentous fungi compared to yeasts. Previous studies showed that the mycelial cell wall of Aspergillus fumigatus lacked β-1,6-glucans, yet a KRE6 ortholog was present in the genome, prompting reinvestigation of β-1,6-glucan occurrence in this fungus.

Objective

This study aimed to determine whether β-1,6-glucans are present in Aspergillus fumigatus and to characterize the function of the Kre6 protein in glucan biosynthesis using solid-state NMR and functional genomic approaches.

Results

ssNMR analysis revealed that β-1,6-glucan is present exclusively in conidial cell walls and absent from mycelial cell walls. Deletion of the KRE6 gene resulted in complete depletion of β-1,6-glucan in conidia with compensatory increase in β-1,3/1,4-glucan. The kre6Δ mutant showed increased sensitivity to cell wall inhibitors Congo Red and Calcofluor White but otherwise exhibited growth phenotype similar to wild-type.

Conclusion

This study demonstrates for the first time that β-1,6-glucans are synthesized in A. fumigatus conidia in a KRE6-dependent manner, highlighting significant structural differences between conidial and mycelial cell walls. Although β-1,6-glucan is not essential for fungal growth, it plays a role in cell wall organization and integrity.
  • Published in:mSphere,
  • Study Type:Research Study,
  • Source: 10.1128/msphere.00341-25, PMID: 40920062
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