Mutation in PMR1, a Ca2+-ATPase in Golgi, confers salt tolerance in Saccharomyces cerevisiae by inducing expression of PMR2, an Na+-ATPase in plasma membrane

Sodium tolerance in yeast is enhanced by continuous activation of calcineur in, a Ca2+/calmodulin-dependent protein phosphatase that is required for mo dulation of the Na+ efflux mechanism. We isolated several salt-tolerant mut ations with the treatment of ethylmethane sulfonate under high salt stress. One of the mutations was mapped in the PMR1 gene. Pmr1p, the P-type Ca2+- ATPase in the Golgi apparatus, regulates a cytosolic Ca2+ level in various responses. Cytosolic Ca2+ concentration in the pmr1 mutant is highly mainta ined, and thus calcineurin is activated continuously. The treatment of FK50 6, a specific inhibitor of calcineurin, abolishes the salt-tolerant phenoty pe of the pmr1 mutant. Activated calcineurin induces the expression of PMR2 , encoding the P-type Na+-ATPase, through the specific transcription factor , Tcn1p/Crz1p. Also, expression of the PMR2::lacZ reporter gene in the pmr1 mutant was higher than that in wild type. We propose that the pmr1 mutatio n confers salt tolerance through continuous activation of calcineurin and t hat Pmr1p might act as a major Ca2+-ATPase under high salt stress.