ChIP ‐seq reveals a role for CrzA in the A spergillus fumigatus high‐osmolarity glycerol response ( HOG ) signalling pathway

A spergillus fumigatus is an opportunistic pathogen and allergen of mammals. Calcium signalling is essential for A . fumigatus pathogenicity and is regulated by the CrzA transcription factor. We used ChIP ‐seq ( C hromatin I mmunoprecipitation DNA sequencing) to explore CrzA gene targets in A . fumigatus . In total, 165 potential binding peaks including 102 directly regulated genes were identified, resulting in the prediction of the A [ GT ][ CG ] CA [ AC ][ AG ] CrzA ‐binding motif. The 102 CrzA putatively regulated genes exhibited a diverse array of functions. The phkB ( A fu3g12530) histidine kinase and the sskB ( A fu1g10940) MAP kinase kinase kinase of the HOG (high‐osmolarity glycerol response) pathway were regulated by CrzA . Several members of the two‐component system ( TCS ) and the HOG pathway were more sensitive to calcium. CrzA :: GFP was translocated to the nucleus upon osmotic stress. CrzA is important for the phosphorylation of the SakA MAPK in response to osmotic shock. The Δ sskB was more sensitive to CaCl 2 , NaCl , and paraquat stress, while being avirulent in a murine model of invasive pulmonary aspergillosis. The presence of CaCl 2 and osmotic stresses resulted in synergistic inhibition of Δ crzA and Δ sskB growth. These results suggest there is a genetic interaction between the A. fumigatus calcineurin‐ CrzA and HOG pathway that is essential for full virulence.