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

Abstract

Sodium tolerance in yeast is enhanced by continuous activation of calcineurin, a Ca(2+)/calmodulin-dependent protein phosphatase that is required for modulation of the Na(+) efflux mechanism. We isolated several salt-tolerant mutations with the treatment of ethylmethane sulfonate under high salt stress. One of the mutations was mapped in the PMR1 gene. Pmr1p, the P-type Ca(2+)-ATPase in the Golgi apparatus, regulates a cytosolic Ca(2+) level in various responses. Cytosolic Ca(2+) concentration in the pmr1 mutant is highly maintained, and thus calcineurin is activated continuously. The treatment of FK506, a specific inhibitor of calcineurin, abolishes the salt-tolerant phenotype 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 mutation confers salt tolerance through continuous activation of calcineurin and that Pmr1p might act as a major Ca(2+)-ATPase under high salt stress.