Characterization of sensor-specific stress response by transcriptional profiling of wsc1 and mid2 deletion strains and chimeric sensors in Saccharomyces cerevisiae.

Cell wall stress in the model yeast Saccharomyces cerevisiae is known to trigger an adaptive transcriptional response. This response is mediated by a specific MAPK cell wall integrity (CWI) signal transduction pathway and affects the expression of many genes whose products are involved in the remodeling of the cellular envelope. Cell wall damage is detected mainly by Wsc1 and Mid2, which are the dominant sensors of CWI pathway. Here, we first determined the transcriptional response to different cell stresses (Congo red, Caspofungin, and Zymolyase) in mid2Δ and wsc1Δ mutant strains using DNA microarrays. Mid2 turned out to be the main sensor involved in the detection of damage provoked by Congo Red, whereas the transcriptional response to Caspofungin is mediated almost exclusively by Wsc1. For stress caused by the degradation of cell wall glucans by Zymolyase, mid2Δ and wsc1Δ deletions show little effect, but the transcriptional response rather depends on the transmembrane protein Sho1, a component of the high-osmolarity glycerol (HOG) pathway. Using sensor chimeras of Wsc1 and Mid2 we studied the contribution of the cytoplasmic and extracellular regions of Mid2 and Wsc1 for sensing Caspofungin-cell wall stress. Genome-wide transcriptional characterization in addition to Slt2 MAPK phosphorylation and phenotypic analyses indicates an important role of the extracellular domain of Wsc1 in mediating signal specificity of this sensor to detect cell wall damage.