The adaptive response of Saccharomyces cerevisiae to weak acids involves the Haa1p-regulon.
Alexandra R. Fernandes (1), Rita C. Vargas (2), Nuno P. Mira (2), Inês Canelhas (2), Isabel Sá-Correia (2)
(1) Biological Sciences Research Group, Centro de Engenharia Biológica e Química, Instituto Superior Técnico, 1049-001 Lisboa, Portugal., Universidade Lusófona de Humanidades e Tecnologias, Campo Grande,376, 1749-029 Lisboa, Portugal; (2) Biological Sciences Research Group, Centro de Engenharia Biológica e Química, Instituto Superior Técnico, 1049-001 Lisboa, Portugal.
The HAA1 gene was proved to be a determinant of Saccharomyces cerevisiae resistance to weak acids: the duration of the adaptation period preceding cell division under weak acid stress was longer for a cell population with this gene deleted. This delay was associated to a more drastic loss of cell viability following sudden exposure of the non-adapted Δ haa1 population to the acids, being maximal for short-chain carboxylic acids (acetic acid followed by propionic acid) and negligible for the more lipophilic benzoic and octanoic acids. The possible involvement in this phenomenon of 10 Haa1-regulated genes [1], many of which are predicted to encode membrane proteins, was examined. Although only YGP1, TPO2 and TPO3 were confirmed to play a role in yeast resistance to acid stress, the yeast response to sudden exposure to weak acids involves their Haa1-dependent transcriptional activation, ranging from 1.5- to 19-fold. YGP1 encodes a putative cell-wall glycoprotein and TPO2 and TPO3 encode proteins predicted to belong to family DHA12 of multidrug resistance transporters of the Major Facilitator Superfamily (MFS) and recently characterized as polyamine transporters located on the plasma membrane. Results also indicate that Haa1 may have other target genes that confer resistance to short-chain carboxylic acids in yeast. [1] Keller, G, Ray, E, Brown, PO, Winge, DR (2001) J. Biol. Chem. 276:38697-38702.