Polymorphism of Saccharomyces cerevisiae aquaporins

Aquaporin water channels facilitate the transmembrane diffusion of water an d higher organisms possess a large number of isoforms. The genome of the ye ast Saccharomyces cerevisiae contains two highly similar aquaporin genes, A QYI and AQY2. AQY1 has been shown to encode a functional water channel but only in certain laboratory strains. Here we show that the AQY2 gene is inte rrupted by an 11 bp deletion in 23 of the 27 laboratory strains tested, wit h the exception of strains from the Sigma 1278b background, which also exhi bit a functional Aqy1p. However, although the AQY2 gene from Sigma 1278b is highly homologous to functional aquaporins, we did not observe Aqy2p-media ted water transport in Xenopus oocytes. A survey of 52 yeast strains reveal ed that all industrial and wild yeasts carry the allele encoding a function al Aqy1p, while none of these strains appear to have a functional Aqy2p. We conclude that natural and industrial conditions provide selective pressure to maintain AQY1 but apparently not AQY2. Copyright (C) 2000 John Wiley & Sons, Ltd.