Figure 1.

Stress activated signaling pathways in Saccharomyces cerevisiae, S. pombe, and Aspergillus nidulans. In S. pombe and A. nidulans, Sty1/Spc1 (HogA/SakA) is activated by environmental stress such as oxidative and osmotic stress and induces transcription factors such as Atf1 (AtfA) for target gene expression. On the other hand, Hog1 activation for Sko1 in S. cerevisiae is dependent on osmotic stress. The TcsA/TcsB/NikA sensor kinases transmit oxidative stress signals to the HogA/SakA SAPK/MAPK cascade through YpdA and SskA in A. nidulans while Sln1 sensor kinase transmits osmotic stress signals to the Hog1 SAPK/MAPK cascade through Ypd1 and Ssk1 in S. cerevisiae. The Skn7 response regulator is also under the Sln1-Ypd1 signal transduction, but oxidative stress appears to activate Skn7 independently of the phosphorelay system. The solid lined arrows indicate signal transduction between two proteins and the dotted arrows indicate signal transduction from oxidative and/or osmotic stress. The thick lined arrows designate binding of transcription factors to target gene promoters. The circles around the proteins indicate transcription factors. Unknown signal transduction between two proteins and unidentified transcription factors are shown by question marks.