Figure 1.

(A) Schematic representation of the cell wall integrity (CWI) signaling pathway in fungi. Stress signals from the cell wall are sensed by receptors (R), which are strongly associated with GTPases such as guanidine nucleotide exchange factors (GEFs) and Ras homologs (RHOs). The phosphorylation cascade begins through the protein kinase C (PKC) that activates by phosphorylation of the MAPK module. After being phosphorylated, the MAPK moves to the nucleus, promoting gene transcription through the activation of specific transcriptional regulators. (B) Secondary metabolites differentially regulated consequent to the inhibition of the CWI signaling. 1,8-dihydroxynaphthalene (a), homogentisate (b), and dihydroxyindol (c) are known precursors of 1,8-dihydroxynaphthalene (DHN)-melanin, l-Dopa melanin, and pyomelanin respectively. Other represented molecules are: gliotoxin (d), ACT toxin (e), beauvericin (f), fusaric acid (g), fumonisin B1 (h), penicillin (i), triacetylfusarinine C (j), and ganoderic acid (k).