Functional analysis of the MAP kinase gene mpkB that possibly contributes to cell wall integrity signaling pathway in Aspergillus nidulans

Akira Yoshimi1, Tomonori Fujioka2, Junichiro Marui1, Daisuke Hagiwara1, Osamu Mizutani3, Kentaro Furukawa4, Keietsu Abe1

Author address: 

1Tohoku University, Sendai, Japan, 2Kumiai Chemical Industry Co., Ltd, Tokyo, Japan, 3National Research Institute of Brewing, Higashihiroshima, Japan, 4Göteborg University, Göteborg, Sweden


The cell wall of filamentous fungi is a complex structure that is essential for the maintenance of cell’s shapes and integrity, for the prevention of cell lysis, and for protection against adverse environmental conditions. Because a mitogen activated protein kinase (MAPK) is a key enzyme of cell wall integrity signaling (CWIS), the transcriptional regulation of MAPK gene and of cell wall-related genes (CWGs) is important in fungal cell wall biogenesis. We previously reported that the transcriptional regulation of the MAPK gene mpkA and of CWGs in Aspergillus nidulans differs significantly from that in Saccharomyces cerevisiae (1). Except for alpha-1,3-glucan synthase genes, the transcription of most CWGs coding for beta-1,3-glucan synthase and chitin synthases were regulated by non-MpkA signaling pathway in A. nidulans (1). A. nidulans possesses a MAP kinase MpkB that has the putative phosphorylation motif TEY (same as that of MpkA), and of which amino acid sequence indicates similar to those of yeast Kss1p and Fus3p. To investigate the in vivo function of the mpkB gene and its possible contribution to CWIS pathway, we constructed A. nidulans mpkB gene disruptant (mpkB8710;) strains. The mpkB8710; strains exhibited increased sensitivity to beta-1,3-glucan synthase inhibitor micafungin as well as the mpkA8710; strain, suggesting that the mpkB gene was also involved in cell wall integrity in A. nidulans. To confirm whether the regulation of CWGs depended on MpkB pathway, we analyzed levels of transcription of CWGs by quantitative RT-PCR. The results suggested that transcription of the agsA gene encoding an alpha-1,3-glucan synthase seemed to be regulated by MpkB-dependent signaling in A. nidulans. Additionally, the phosphorylation pattern of MpkA and MpkB induced by micafungin was assessed. Transcriptional analyses of mpkA8710; and mpkB8710; strains with DNA microarrays will be also discussed.

abstract No: 


Full conference title: 

    • ECFG 9th (2008)