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

Abstract

Disruption of the kexB encoding a subtilisin-like processing protease in Aspergillus oryzae (ΔkexB) leads to substantial morphological defects when the cells are grown on Czapek-Dox agar plates. We previously found that the disruption of kexB causes a constitutive activation of the cell wall integrity pathway. To understand how the disruption of the kexB affects cell wall organization and components, we analyzed the cell wall of ΔkexB grown on the plates. The results revealed that both total N-acetylglucosamine content, which constitutes chitin, and chitin synthase activities were increased. Whereas total glucose content, which constitutes β-1,3-glucan and α-1,3-glucan, was decreased; this decrease was attributed to a remarkable decrease in α-1,3-glucan. Additionally, the β-1,3-glucan in the alkali-insoluble fraction of the ΔkexB showed a high degree of polymerization. These results suggested that the loss of α-1,3-glucan in the ΔkexB was compensated by increases in the chitin content and the average degree of β-1,3-glucan polymerization.

Summary of the alteration in the cell wall composition of the A. oryzae ∆kexB.

Key words:

• Aspergillus oryzae
• processing protease (KexB)
• cell wall integrity
• α-1,3-glucan

Acknowledgments

We thank Dr Youji Kato, Dr Kentaro Furukawa, and Dr Tomonori Fujioka for helpful suggestions. The generous gift of TFA-treated soluble curdlan from Dr Seiji Oyama is highly appreciated. The generous gift of an α-1,3-glucanase from Dr Shigekazu Yano and Dr Takashi Tachiki is also highly appreciated.

Notes

Abbreviation: CWIS, cell wall integrity signaling.

Additional information

Funding

This work was supported by the Japan Society for the Promotion of Science [KAKENHI Grant-in-Aid for Scientific Research (B) grant number 26292037].