Substantial decrease in cell wall α-1,3-glucan caused by disruption of the kexB gene encoding a subtilisin-like...

Area of Science:

• Mycology
• Biochemistry
• Cell Biology

Background:

• The kexB gene encodes a subtilisin-like protease crucial for fungal development.
• Disruption of kexB in Aspergillus oryzae leads to morphological defects and constitutive activation of the cell wall integrity pathway.
• Understanding cell wall composition changes is key to explaining these phenotypes.

Purpose of the Study:

• To investigate the impact of kexB disruption on the cell wall composition of Aspergillus oryzae.
• To elucidate the relationship between kexB function, cell wall integrity, and cell wall component alterations.

Main Methods:

• Analysis of cell wall components in wild-type and ΔkexB Aspergillus oryzae strains.
• Quantification of N-acetylglucosamine (chitin) and glucose (glucans) content.
• Assay of chitin synthase activities.
• Determination of glucan polymerization degree.

Main Results:

• ΔkexB strains showed increased N-acetylglucosamine content and chitin synthase activity.
• Total glucose content was decreased, primarily due to a reduction in alpha-1,3-glucan.
• Beta-1,3-glucan in the alkali-insoluble fraction exhibited a higher degree of polymerization in ΔkexB.

Conclusions:

• The loss of alpha-1,3-glucan in ΔkexB mutants is compensated by increased chitin and enhanced beta-1,3-glucan polymerization.
• These compositional changes likely contribute to the observed morphological defects and altered cell wall integrity pathway activation.
• The study highlights the intricate regulation of fungal cell wall biosynthesis and integrity.