Here we show that the TGN complex named exomer is required for alkali cation tolerance in yeast because of its roles in the sorting and polarization of the plasma membrane Na+-ATPase Ena1 and on the signal processing through the RIM101 pathway, thus widening the functional repertoire of the yeast exomer.

30Yeast exomer is a heterotetrameric complex assembled at the trans-Golgi 31 network (TGN) that is required for the delivery of a distinct set of proteins to the plasma 32 membrane using ChAPs proteins Chs6 and Bch2 as dedicated cargo adaptors. Our 33 results show, however, a significant functional divergence between them, suggesting an 34 evolutionary specialization among the ChAPs proteins. Moreover, the characterization 35 of exomer mutants in several fungi indicates that exomer function as a cargo adaptor is 36 a late evolutionary acquisition associated with several gene duplications of the fungal 37