Cell wall stress sensor. Involved in activation of a response that includes both stress-related increased chitin synthesis and the MPK1 mitogen-activated protein kinase cell integrity pathway. High-copy activator of the SKN7 transcription factor. Required during induction of MPK1 tyrosine phosphorylation under a variety of stress conditions. Required for PKC pathway activation under low pH conditions. Required for cell integrity signaling during pheromone-induced morphogenesis. Activates ROM1 or ROM2 catalyzed guanine nucleotide exchange toward RHO1 in cell wall integrity signaling. Interacts with ZEO1. Localizes uniformly around the cell periphery. Also localized to the mother-bud junction. O-mannosylated by PMT2. Belongs to the MID2 like cell wall stress sensor family.