Abstract: Type 2C protein phosphatases are encoded in Saccharomyces cerevisiae by several related genes (PTC1-5 and PTC7). To gain insight into functions attributable to specific members of this gene family, we have investigated the transcriptional profiles of ptc1-5 mutants. Two main patterns were obtained: the one generated by the ptc1 mutation and the resulting from lack of Ptc2-5. ptc4 and ptc5 profiles were quite similar, while that of ptc2 was less related to this group. Mutation of PTC1 resulted in increased expression of numerous genes that are also induced by cell wall damage, such as YKL161c, SED1 or CRH1, as well as in higher amounts of active Slt2 MAP kinase, indicating that lack of the phosphatase activates the cell wall integrity pathway. ptc1 cells were even more sensitive than slt2 mutants to a number of cell wall damaging agents and both mutations had additive effects. The sensitivity of ptc1 cells was not dependent on Hog1. Besides these phenotypes, we observed that calcineurin was hyperactivated in ptc1 cells, which also were highly sensitive to calcium ions, heavy metals and alkaline pH, and exhibited a random haploid budding pattern. Remarkably, many of these traits are found in certain mutants with impaired vacuolar function. As ptc1 cells also display fragmented vacuoles, we hypothesized that lack of Ptc1 would primarily cause vacuolar malfunction, from which other phenotypes would derive. In agreement with this scenario, overexpression of VPS73, a gene of unknown function involved in vacuolar protein sorting, largely rescues not only vacuolar fragmentation, but also sensitivity to cell wall damage, high calcium, alkaline pH, as well as other ptc1 specific phenotypes.