FIG. 7.

Schematic model for implication of the cell integrity pathway in the ΔkexB (A) and wild-type (B) strains. The cell integrity MAP kinase pathway is shown by the dotted box. pkcA (47), mpkA (7), and rlmA (Fujioka et al., unpublished; accession no. BAD01583) were isolated from Aspergillus fungi. The yeast BCK1 and MKK1 orthologs have not yet been isolated from Aspergillus species; however, putative ORFs (bckA, mkkA) homologous to the two genes are found in A. oryzae genome sequences (O. Mizutani, K. Abe, and T. Nakajima, unpublished data). The cell integrity pathway in the ΔkexB strain is constitutively activated (A), although the pathway is not activated (resting) unless the wild-type strain senses some stress such as hypoosmolarity (B). A. oryzae KexB is predicted to be required for precise proteolytic processing of sensor proteins in the cell integrity pathway and/or of cell wall-related enzymes whose genes are under transcriptional control by the pathway.